Department of Pharmaceutics, College of Pharmaceutical Sciences, Govt. Medical College, Thiruvananthapuram, Kerala, India
In recent years more nanomaterials has been incorporated into biosensors for clinical applications such as the disease diagnosis and therapeutic drug monitoring. Because of their high sensitivity and quick response, nanomaterial-assisted biosensors have great importance as platforms for pharmaceutical research and disease diagnosis. The efficiency of biosensors has been significantly improved by using nanomaterials like gold nanoparticles, silver nanoparticles, nanocomposites, graphene, metal oxide nanoparticles, quantum dots, and carbon tube. They enable signal amplification, increase electron transfer kinetics and increase active surface area for biomolecule immobilization. These nanomaterial-incorporated biosensors are widely used to support early detection and point-of-care testing by detecting inflammatory proteins, glucose, infectious disease targets, cardiac markers, and cancer biomarkers. Nanomaterial-based biosensors are crucial for drug discovery, enzyme inhibition studies, therapeutic drug monitoring, pharmaceutical quality control, and personalized medicine in pharmaceutical research. These biosensors have advanced applications but also have challenges in reproducibility, stability of biological recognition elements, matrix interference in clinical samples and toxicity concerns of some nanomaterials are significant obstacles to commercialization. The recent advancements in nanomaterial-assisted biosensors, their signal enhancement mechanisms, their clinical and pharmaceutical applications, and future trends like wearable biosensors, microfluidic lab-on-a-chip systems, and artificial intelligence-integrated sensing platforms represent a major step toward highly sensitive, rapid, and point-of-care diagnostic technologies. This review focuses on these innovations which enable rapid, accurate, and real time detection in diverse healthcare settings.
Biosensors are analytical devices that combine a biological recognition element with a physicochemical transducer to detect specific analytes with high selectivity and sensitivity. Over the past two decades, biosensor technology has gained tremendous attention in clinical diagnostics, pharmaceutical research, and environmental monitoring. The increasing burden of chronic diseases such as cancer, diabetes, cardiovascular disorders, and infectious diseases has created an urgent demand for rapid, cost-effective, and reliable diagnostic platforms. Conventional diagnostic techniques such as enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), high-performance liquid chromatography (HPLC), and mass spectrometry provide accurate results but require expensive instrumentation, skilled personnel, and time-consuming procedures. Therefore, biosensors have become promising alternatives due to their simplicity, portability, and potential for real-time monitoring. [6,15] Recent developments in nanotechnology have significantly transformed biosensor design and performance. Nanomaterials possess unique physical and chemical properties such as high surface-to-volume ratio, enhanced electrical conductivity, catalytic activity, tunable optical properties, and biocompatibility. These properties allow nanomaterials to improve the sensitivity and detection limit of biosensors, enabling the detection of analytes even at femtomolar or picomolar concentrations. Nanomaterials also provide an ideal surface for immobilisation of biological recognition elements such as antibodies, aptamers, enzymes, and nucleic acids, improving stability and signal output.[12] Nanomaterial-assisted biosensors are increasingly applied in clinical diagnosis for the detection of biomarkers associated with cancer, cardiac diseases, neurological disorders, and infectious diseases. These biosensors have shown significant advantages in point-of-care testing (POCT), where rapid diagnosis is essential for timely clinical decision-making. Additionally, biosensors have become valuable tools in pharmaceutical research, supporting drug screening, evaluation of drug-protein interactions, therapeutic drug monitoring (TDM), pharmacokinetic studies, and quality control analysis of pharmaceutical formulations. The integration of nanomaterials with microfluidic devices, wearable sensors, smartphone-based readout systems, and artificial intelligence (AI) algorithms has further accelerated the development of next-generation biosensing platforms.[3] Despite these advantages, challenges remain in terms of reproducibility, fabrication complexity, long-term stability, interference from complex biological matrices, and standardisation for clinical use. Furthermore, concerns regarding the toxicity and environmental impact of certain nanomaterials must be addressed to ensure safe clinical translation. Therefore, a comprehensive understanding of nanomaterial-based biosensors is essential for their development into reliable diagnostic and pharmaceutical research tools.[2] This review focuses on recent developments in nanomaterial-assisted biosensors, discussing different types of nanomaterials used in biosensing, their signal amplification mechanisms, and their wide applications in clinical diagnosis and pharmaceutical research. The review also highlights current limitations and future perspectives, emphasising the importance of clinical validation, commercialisation strategies, and regulatory approval pathways for the successful implementation of nano-enabled biosensors.
2. Biosensors: Principle And Classification
A biosensor is an analytical device that converts a biological response into a measurable signal. The basic components of a biosensor include (i) a biological recognition element (bioreceptor), (ii) a transducer, and (iii) a signal processing/display system. The bioreceptor selectively interacts with the target analyte, while the transducer converts this interaction into a quantifiable electrical, optical, or mechanical signal. The generated signal is then amplified and processed to provide a readable output.[26]
Figure 1: Parts of biosensor
The bioreceptor plays a crucial role in the selectivity of biosensors. Commonly used bioreceptors include enzymes, antibodies, nucleic acids, aptamers, whole cells, and molecularly imprinted polymers. The choice of bioreceptor depends on the target analyte and the intended application. For example, enzymes are widely used for glucose biosensing, antibodies are preferred for immunosensors targeting proteins and cancer biomarkers, and nucleic acids are used for DNA/RNA detection in infectious diseases. Based on the type of signal transduction, biosensors are classified into electrochemical, optical, piezoelectric, and thermal biosensors.
2.1 Electrochemical Biosensors
Electrochemical biosensors are the most widely used biosensors due to their high sensitivity, low cost, portability, and compatibility with miniaturised devices. These biosensors detect analytes by measuring changes in electrical properties such as current, potential, or impedance. Electrochemical biosensors are further classified into amperometric, potentiometric, conductometric, and impedimetric biosensors.
2.1.1 Potentiometric Sensors
In potentiometric sensors, a very small current is allowed to measure the potential difference between the reference electrode and the indicator electrode without polarising the electrochemical cell. The reference electrode is meant for providing a constant half-cell potential, while the indicator electrode exhibits a variable potential depending upon the concentration of a specific analyte in a solution. The potential change is related to the logarithm of concentration. Mostly, a potentiometric sensor comprises a membrane (either a solid like glass and inorganic crystal or a plasticised polymer) with a unique composition and the ISE composition is chosen to indicate a potential that is primarily associated with the ion of interest via a selective binding process at the membrane-electrolyte interface.[15]
2.1.2 Amperometric Sensors
Amperometry is a method of electrochemical analysis in which the signal of interest is current, and it is linearly dependent upon the concentration of the analyte. As the chemical species are oxidised or reduced (redox reactions) on inert metal electrodes, electrons are transferred from the analyte to the working electrode or vice versa. The electron flow direction depends upon the properties of the analyte, and it can be controlled by the potential applied to the working electrode. Two or three electrodes may be present in an amperometric cell. Usually, the working electrode is a noble metal like platinum (Pt) or gold (Au), and the potential applied to the working electrode is measured and controlled by a reference electrode, usually Ag/AgCl, that provides a fixed potential. Sometimes a third electrode, known as the counter or the auxiliary electrode, is also used. By amperometric measurement, a linear current vs. ion-concentration characteristics can be obtained using diffusion-controlled processes in the limiting current operating mode. The measured cell current, i.e. the diffusion current, determines the analyte concentration quantitatively. Based on the amperometric measurements, there are three “generations” of biosensors due to the different electron transfer processes. First-generation biosensors cause the electrical response because of the diffusion of the normal product of the reaction to the transducer, and the second-generation biosensors involve specific “mediators” between the reaction and the transducer for the improved response. In the third-generation biosensors, the reaction itself causes the response without the direct involvement of any product or mediator diffusion.
2.1.3 Conductometric Sensors
Conductometric sensors measure the electrolyte conductivity that varies when the cell is exposed to different environments. The sensing effect is due to the change in the number of mobile charge carriers in the electrolyte. The electrolyte shows ohmic behaviour with the non-polarised electrodes in the AC supply mode operations during conductometric measurements. Since the conductivity is a linear function of the ion concentration in the electrolyte, the method can be used for sensor applications. However, it is nonspecific for a given type of ion, and so it functions as a non-selective sensor. The most essential conditions for using this sensor are the absence of polarisation and limiting current operation mode. Thus, small amplitude alternating bias is used for the measurements with frequencies where the capacitive coupling is still not determining the impedance measurement.
2.2 Optical Biosensors
Optical biosensors detect biological interactions by measuring changes in light properties such as absorbance, fluorescence, luminescence, or refractive index. Optical biosensors are highly suitable for real-time monitoring and multiplexed detection. Techniques such as surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence resonance energy transfer (FRET), and colourimetric detection are commonly employed. Nanomaterials such as gold nanoparticles, quantum dots, and plasmonic nanostructures have greatly enhanced optical biosensor performance by improving signal intensity and detection sensitivity.[16]
2.3 Piezoelectric Biosensors
Piezoelectric biosensors detect changes in mass or mechanical properties on the sensor surface by measuring changes in resonance frequency. Quartz crystal microbalance (QCM)-based biosensors are widely used examples. When biomolecules bind to the sensor surface, the mass change results in a frequency shift, which can be correlated with analyte concentration. These biosensors offer label-free detection and are useful for studying biomolecular interactions, drug binding studies, and protein analysis.
2.4 Thermal Biosensors
Thermal biosensors detect changes in temperature generated during biochemical reactions. These sensors measure the heat produced or absorbed when analytes interact with enzymes or biological components. Although thermal biosensors provide direct measurement of biochemical reactions, they are less commonly used compared to electrochemical and optical biosensors due to limited sensitivity and higher instrumentation requirements.[6]
3. Nanomaterials Used In Biosensors
Nanomaterials are defined as particles with at least one dimension in the nanoscale range (1–100 nm). Due to their unique physicochemical properties, nanomaterials have become essential components in modern biosensors. Their high surface area, enhanced electrical conductivity, catalytic activity, and tunable optical properties significantly improve biosensor performance. In addition, the enlarged surface area also allows larger amounts of electric current or light to be delivered to optical or electrochemical detectors. Nanomaterials also provide an excellent platform for immobilisation of bioreceptors, resulting in enhanced stability and higher biomolecule loading. The major classes of nanomaterials used in biosensors include metallic nanoparticles, carbon-based nanomaterials, metal oxide nanomaterials, quantum dots, and nanocomposites.
3.1 Metallic Nanoparticles
Metallic nanoparticles such as gold (AuNPs), silver (AgNPs), platinum (PtNPs), and palladium nanoparticles are extensively used in biosensor fabrication. Among these, AuNPs are most widely applied due to their excellent biocompatibility, chemical stability, ease of functionalization, and strong conductivity. Gold nanoparticles (AuNPs), also known as gold colloids or colloidal gold, are nanometre-sized spheres made primarily of gold. Typically, AuNPs range from 1 to 50 nm in size. Despite the availability of other types of metallic nanoparticles, AuNPs are preferred in biosensing due to their superior stability. In addition, gold itself does not show any adverse effect to the bioreceptors, which can easily be conjugated to AuNPs using thiol (–SH) chemistry. AuNPs do not destroy or denature target biomolecules, while many other metal nanoparticles do (e.g., silver nanoparticles destroy most bacteria). The overall larger surface area accommodates a higher number of bioreceptors to be used for a given volume, enhancing the optical or electrochemical signals and signal-to-noise ratio (S/N ratio). AuNPs have also been a popular subject for catalysis and enzyme studies, again due to the larger surface area. Gold nanoparticles enhance biosensor performance by increasing electrode surface area and facilitating electron transfer between redox-active species and the electrode. They also support stable immobilisation of antibodies, enzymes, and nucleic acids through thiol-gold bonding. Silver nanoparticles are frequently used in optical biosensors due to their strong plasmonic properties and ability to enhance Raman signals. Platinum nanoparticles exhibit excellent catalytic properties and are widely used in biosensors for hydrogen peroxide and glucose detection. These nanoparticles improve sensitivity by accelerating electrochemical reactions.
3.2 Carbon-Based Nanomaterials
Carbon nanomaterials have attracted strong interest in biosensor development due to their high conductivity, mechanical strength, and large surface area. Major carbon nanomaterials include carbon nanotubes (CNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), and carbon dots. CNTs improve electron transfer kinetics and provide a porous network structure for immobilisation of biomolecules. Graphene and its derivatives offer a large surface area, high conductivity, and strong adsorption capability, enabling highly sensitive detection of biomolecules. Carbon dots are fluorescent nanomaterials used in optical biosensors due to their tunable emission and biocompatibility. Pure carbon molecules can be interconnected to form hexagonal or honeycomb-shaped structures. If these structures form a single-layered, two-dimensional sheet, it becomes graphene. If they make a cylindrical tube, it becomes CNTs. The existence of hexagon-shaped structures made purely out of carbon has long been speculated since the 1950s, but the actual isolation and synthesis came relatively later. CNTs can be made as single-walled tubes, referred to as single-wall carbon nanotubes (SWCNTs), or with multiple layers of tubes, referred to as multiwall carbon nanotubes (MWCNTs). The highly ordered structure of CNTs creates remarkable tensile strength and high resistivity, while the atomic-scale cylindrical structure provides excellent flexibility (i.e., it can easily be bent without being broken). These unique features have prompted many scientists and engineers to develop much more durable yet resilient materials. Just like other nanomaterials, the surface-to-volume ratio of CNTs is high. This feature leads to more bioreceptor immobilisation and improved signal transduction. Conjugation of bioreceptors to CNTs is difficult, since CNTs are made purely out of carbon. Typically, carboxyl groups are added to CNTs to accommodate their binding to the amine groups on bioreceptors. It is possible to utilise electrostatic attraction or hydrogen bonding between these carboxyl and amine groups. However, the better-practised method is to utilise carbodiimide (in the form of RN = C=NR’), to covalently conjugate the carboxyl group on CNTs with the amine group on bioreceptors. This forms a very stable peptide bond (–CO–NH–) between the CNTs and bioreceptors. Alternatively, polymer coatings can be added to CNTs, similar to the QDs, followed by a linker molecule such as streptavidin/biotin or protein. Similar to CNTs, graphene can also provide remarkable strength, stiffness, and stability, which can be utilised for various materials applications. Graphene can be made into single or multi-layered sheets, analogous to CNTs. Specifically, for graphene, excellent heat and electricity conductance have been noted, which is an important characteristic useful in electrochemical biosensing. Graphene is essentially a single-atom-thick (for a single layer) sheet of carbon atoms in a honeycomb pattern. This unique structure allows for extremely rapid electron transfer kinetics. Similar to ZnO nanostructure-based biosensors, these electrochemical signals can be amplified via FET devices. Due to these characteristics, graphene has been popularly evaluated for electrochemical kinetic measurements, such as cyclic voltammetry or electrochemical impedance spectroscopy (EIS). GO is less robust, has a higher detection limit, and shows slower electron transfer than graphene. For both graphene and GO, DNA probes can be formed into hairpin shapes and can be subsequently stacked on top of a hexagonal carbon structure, utilising π-stacking interactions, thus requiring no chemical modification to graphene. Upon binding to a target DNA sequence, the hairpin structure opens up, leading to a significant decrease in the charge transfer resistance. Similar to other nanomaterials, both CNTs and graphene sheets can be deposited onto an electrode surface, and secondly, bioreceptors can be conjugated onto them. The reported detection limits are again in the range of 1–10 μm for most chemicals, roughly equivalent to a few tens of ng/ml. The detection limits for CNTs or graphene in DNA and biomolecule sensing are quite low, typically in the range of pM or sub-pM scale. The mismatch of a single base pair (known as a single-nucleotide polymorphism or SNP) can be detected with this approach, meaning excellent selectivity and sensitivity. A nano-porous gold electrode surface (GCE or graphene) is used for a sandwich immunoassay (e.g., cancer marker detection using an antibody to cancer marker) in conjunction with an enzyme (e.g., horseradish peroxidase, HRP)
3.3 Metal Oxide Nanomaterials
Various nanostructures can be fabricated using metal oxide materials based on copper, iron, nickel, tin, titanium, zinc, or zirconium. Due to their oxidised status, they are not charged but still hydrophilic, thus quite biocompatible, which is a good trait for biosensor applications. Various types of nanostructures have been fabricated using metal oxides such as nanobelts, nanocombs, nanofibers, nanoflakes, nanoforks, nanonails, nanoneedles, nanopores, nanorods, nanosheets, nanoparticles, nanotubes, nanowalls, etc. These nanostructures provide high surface-to-volume ratios, allowing for higher loading of bioreceptors, as well as catalytic capability (similar to AuNPs). ZnO nanostructures are particularly popular in biosensor applications, due to their low material cost, nontoxicity, and high surface charge (advantageous for electrochemical biosensing). ZnO can easily be incorporated into complementary metal–oxide–semiconductors. This similarity allows them to be jointly incorporated into small, integrated biosensor devices. Due to the compatibility with semiconductor devices, ZnO nanostructures have primarily been evaluated for use in electrochemical biosensors. In addition, electrochemical signals from ZnO nanostructure-based biosensors can also be amplified and transmitted via field-effect transistor (FET) devices, allowing for the possibility of wireless remote biosensing. ZnO is a widely used nanomaterial due to its biocompatibility, high isoelectric point, and strong adsorption capacity for proteins. TiO? is commonly used in photocatalytic biosensors and surface modification. Fe?O? nanoparticles are magnetic and are frequently used for the separation and enrichment of biomarkers in clinical samples. Cerium oxide nanoparticles exhibit enzyme-like activity (nanozymes), enabling signal amplification in biosensors. Typical detection limits are 1–10 μm for most chemicals (glucose, cholesterol, alcohol, lactic acid, etc.), which is roughly equivalent to a few tens of ng/ml. These numbers are essentially within the same range as AuNP-enhanced biosensors. Similar to AuNP-enhanced biosensors, ZnO nanostructure-enhanced biosensors can also be used for immunoassays (ELISA), aptasensors as well as DNA sensors, again with improved sensitivity and lower detection limits
3.4 Quantum Dots
Quantum dots are semiconductor nanocrystals with excellent fluorescence properties, high photostability, and tunable emission wavelengths. They typically comprise two different semiconductor materials like lead sulphide, lead selenide and cadmium sulphide. Unlike gold nanoparticles, quantum dots do exhibit some toxicity to cells and potentially denature some proteins. They are widely applied in optical biosensors for the detection of DNA, proteins, and cancer biomarkers. Quantum dot-based biosensors often provide higher sensitivity compared to conventional fluorescent dyes due to their strong brightness and resistance to photobleaching.
3.5 Polymeric Nanomaterials and Nanocomposites
Polymeric nanomaterials such as conducting polymers (polyaniline, polypyrrole) and polymer-based nanoparticles are also used for biosensor fabrication. These materials provide good flexibility, biocompatibility, and stable immobilisation environments for bioreceptors. Nanocomposites are hybrid materials formed by combining two or more nanomaterials, such as AuNP-graphene, CNT-metal oxide, or polymer-metal nanoparticle composites. Nanocomposites offer synergistic effects, including improved conductivity, stability, and signal amplification. These hybrid materials are particularly useful in electrochemical biosensors for clinical diagnosis due to their improved sensitivity and selectivity.[21]
Table 1: Different types of nanomaterials and clinical examples
|
Type of Nanomaterial |
Key Properties |
Clinical Examples |
Pharmaceutical Uses |
|
Metallic Nanoparticle |
Plasmonic effects, easy conjugation |
LSPR for PSA detection (1 pg/mL), SERS for miRNA |
Antibiotic residue sensing (e.g., tetracycline at nm) |
|
Carbon |
2D conductivity, mechanical strength |
FETs for COVID-19 antigens (10 fg/mL), dopamine in CSF |
Metabolite profiling (e.g., paracetamol oxidation) |
|
Quantum dots |
Size-tunable emission, multiplexing |
FRET-based cardiac troponin assays |
Liposome drug release tracking |
|
MXenes |
Hydrophilicity, metallic conductivity |
Sweat glucose wearables (5 μm LOD) |
Nanoformulation stability tests |
|
Nanozymes |
Enzyme-like activity, stability |
Peroxidase-mimicking for H2O2 in wounds |
Oxidative stress biomarkers in drug trials. |
4. Role Of Nanomaterials In Signal Enhancement
Nanomaterials significantly strengthen biosensor sensitivity and its performance. They can be explained through multiple mechanisms. Nanomaterials increase the surface area and the number of binding sites available for the immobilisation of antibodies, enzymes, or aptamers, thereby increasing bioreceptor loading and enhancing reactions with analytes. They enhance the transfer of electrons between the electrode and analyte, which generates electrochemical responses. Metallic nanoparticles and carbon-based nanomaterials will give higher conductivity, thereby reduce resistance and increase current output. Many of the nanomaterials have catalytic properties. Platinum nanoparticles, metal oxide nanoparticles, and nanozymes accelerate redox reactions, which help to amplify signals. Nanomaterials such as AuNPs and AgNPs enhance optical signals through localised surface plasmon resonance (LSPR), which enables colourimetric and SPR-based detection. Magnetic nanoparticles help in sample preparation and biomarker enrichment, which improves detection in complex biological fluids like serum and plasma. That’s why nanomaterial-assisted biosensors have greater sensitivity and analytical performance.[14]
5. Immobilization Techniques
5.1. Drop-Casting: It is a deposition method in which nanoparticles in solution are manually deposited on the electrode, which leads to the formation of thin films on electrode surfaces. Nanomaterials, that is mixed with binders, are widely used for such fabrication of thin films on the electrode surface. A homogeneous dispersion is prepared by mixing nanomaterials often with a binder in a solvent, which is then drop-casted to the electrode surface and dried. Various nanomaterials, such as metallic, carbonaceous, and their hybrids, are used for the casting method. Drop casting of conductive nanoparticles on the electrode surfaces offers better electrochemical properties.
5.2. Dip-Coating: The substrate is immersed in a coating solution for a definite time period and withdrawn vertically at a fixed speed, following solvent evaporation. The withdrawal speed and the evaporation condition play an important role in the film formation process. Nanomaterials can be deposited using the dip-coating method on the electrode surface. Dip-coating requires a considerable volume of the coating solution for immersion. This is a critical issue for cases: (a) when the solution is not stable enough over time; (b) when the handling of a large volume of the solution is risky, and the solution is harmful, or (c) when it is expensive or can only be synthesised in small quantities.
5.3. Spin-Coating. It is also used for thin-film fabrication. The process involves casting a solution of interest onto the substrate, which is then spread across the substrate by spinning it. During the spinning step, some amount of solution may be expelled from the surface. The solution remaining on the substrate surface forms the shape of a thin film once solvent evaporation completes. The thickness of the thin film can be controlled by altering the spin speed and concentration of the solution used for casting. Besides, multilayer films may also be deposited by repeating the above steps. Polymers are extensively used for spin coating due to their good film-forming characteristics and ability to allow functional modification in them. It is another commonly used technique for nanomaterial deposition during bioelectrode fabrication. Spin coating is often used during the fabrication of microelectrodes through photolithography. Before performing photolithography, a photoresist is deposited on the electrode surface, usually by the spin-coating method. The spin coating method is adapted for fabricating thick, multilayer, uniform films.
5.4. Electrochemical Deposition: This thin film deposition technique utilises a three-electrode system (Working electrode, Reference Electrode, and Counter Electrode), which is dipped into a solution containing the components to be deposited. The deposition on the working electrode can be done using the following various methods. It is mostly done by applying a constant potential at the working electrode or by sweeping the potential for multiple cycles using CV. Other methods, such as constant current techniques, are also explored for the depositions. In this method, the morphologies of the deposited particles are controlled by the applied current density.
5.5. Electrospray Deposition (ESD). Here, a small capillary is used through which the solution of interest flows. The capillary is separated by a few millimetres from the counter electrode and held at a high voltage of a few kV, which results in the generation of charged molecules. At the tip of the capillary, a typical cone-like shape, known as a “Taylor cone”, forms where the repulsion of these charged molecules is counterbalanced by the liquid’s surface tension. Once a critical point is achieved where the liquid’s surface tension cannot hold the charged molecules further, a Coulomb explosion takes place that results in a fine jet of charged droplets issuing from the apex of the cone. The size of these charged droplets reduces further due to solvent evaporation, and finally, a gas of molecular ions forms, moving toward the counter electrode. This technique has even been used to develop a prototype for a paper-based cholesterol biosensor, where a nanocomposite prepared from graphene, polyvinylpyrrolidone (PVP), and polyaniline (PANI) was deposited on a paper using electro-spraying.[12]
6. Applications In Clinical Diagnosis
6.1. Cancer Diagnosis
A cancer diagnosis needs the detection of biomarkers at very low concentrations. Nanomaterial-assisted biosensors will give sensitive detection by using nanomaterials as conductive substrates, signal amplifiers, and immobilisation matrices. Early detection improves the survival rate and reduces metastatic progression. Nanomaterials such as gold nanoparticles, graphene, carbon nanotubes and quantum dots can be used in the biosensor.
6.2. Infectious Disease Diagnosis
Nanomaterial-based biosensors provide rapid and accurate identification of pathogens in clinical samples. They significantly reduce diagnostic time compared to conventional culture and molecular methods. Gold nanoparticles and magnetic nanoparticles enhance target binding, signal transduction, and sensitivity, making them ideal for outbreak control and point-of-care testing.
6.3. Cardiovascular Disease Diagnosis
These biosensors enable early diagnosis of myocardial infarction and heart failure by detecting cardiac biomarkers in blood. Nanomaterials improve electron transfer efficiency and signal amplification, allowing rapid and highly sensitive detection, especially in emergency clinical settings.
6.4. Diabetes Monitoring
Nanomaterial-based biosensors enable continuous glucose monitoring systems with high sensitivity and real-time output. Materials such as graphene, ZnO nanoparticles, and platinum nanoparticles enhance enzymatic and non-enzymatic glucose sensing, supporting improved diabetes management.[8]
6.5. Neurological Disease Diagnosis
These biosensors detect ultra-low levels of neurodegenerative biomarkers in blood and cerebrospinal fluid. Nanomaterials enhance sensitivity and selectivity, enabling early diagnosis before clinical symptoms become severe.[24]
6.6. Hormonal and Metabolic Disorder Detection
Nanobiosensors enable rapid hormone quantification in serum and saliva. They provide improved sensitivity compared to conventional immunoassays and support real-time endocrine monitoring.[6]
7. Applications In Pharmaceutical Research
In pharmaceutical research, these biosensors play critical roles across multiple stages, from early drug discovery to quality control, therapeutic monitoring, and pharmacokinetic studies.
7.1 Detection and Quantification of Pharmaceutical Compounds
Nanomaterial-based electrochemical and optical biosensors enable sensitive, real-time detection of active pharmaceutical ingredients (APIs), impurities, and metabolites in complex matrices like biological fluids, formulations, or environmental samples. They support high-throughput screening and quality assurance in drug manufacturing. Electrochemical sensors: Often use gold nanoparticles (AuNPs), carbon nanotubes (CNTs), graphene, or metal oxide nanocomposites for detecting drugs such as antibiotics (e.g., tetracycline), anticancer agents, analgesics (e.g., acetaminophen), and neurotransmitter-related compounds. These platforms offer low limits of detection (often nanomolar to femtomolar) and are useful for stability testing and impurity profiling.[12] Optical biosensors: Leverage quantum dots (QDs), graphene quantum dots (GQDs), or plasmonic nanoparticles (e.g., AuNPs) for fluorescence, surface plasmon resonance (SPR), or colourimetric detection. They are applied in monitoring drug-nanoformulations and molecular-level interactions. Examples include sensors for specific drugs like nifedipine, levodopa, progesterone, or neuropharmaceuticals, where nanomaterials enhance electrocatalytic activity or fluorescence quenching/amplification.
7.2 Therapeutic Drug Monitoring (TDM) and Pharmacokinetics
Biosensors facilitate continuous or point-of-care monitoring of drug concentrations in blood, plasma, or tissues, aiding personalised dosing, bioavailability assessment, and pharmacokinetic/pharmacodynamic (PK/PD) studies. Nanomaterials improve signal stability and enable integration with wearable or microfluidic devices for real-time data. Applications in anticancer drug monitoring, where nanomaterials boost sensitivity for low-concentration analytes in complex biofluids. Optical nanomaterial-based systems for molecular drug or nano-drug tracking in biopharmaceutical development, supporting at-home diagnostics and continuous monitoring.[16]
7.3. Drug Discovery and Screening
In high-throughput screening, nanomaterial-enhanced biosensors detect biomolecular interactions, enzyme inhibition, or receptor binding relevant to drug candidates. They accelerate identification of hits by providing label-free or amplified readouts for small molecules, proteins, or nucleic acids. Integration with aptamers or enzymes on platforms like graphene or CNTs for screening anticholinesterase drugs, dopamine-related compounds, or other targets. Use in detecting biomarkers or cellular responses during preclinical studies, including neuropharmaceutical compounds and their effects on neurotransmitters.[12]
7.4. Analysis of Drug Delivery Systems and Nanoformulations
Nanomaterials in biosensors help characterise nanoparticle-based drug carriers (e.g., liposomes, polymeric NPs) by monitoring release kinetics, targeting efficiency, or stability. Conversely, the same nanomaterials (e.g., AuNPs, CNTs) are often components of both the delivery system and the sensing platform. Support for evaluating the pharmacokinetics of nanoparticles themselves, including biodistribution and cellular uptake. Biosensor-integrated systems for controlled drug release and health management, combining sensing with delivery (e.g., redox-responsive mesoporous silica nanoparticles).[16]
7.5. Other Emerging Applications
Detection of counterfeit or substandard drugs. Environmental monitoring of pharmaceutical residues (e.g., antibiotics in wastewater). Integration with point-of-care testing (POCT) devices, microfluidics, or AI for multiplexed analysis in pharmaceutical R&D. Advantages in pharmaceutical contexts include miniaturisation, cost-effectiveness, reduced sample volumes, and compatibility with complex matrices, outperforming traditional techniques like HPLC or spectroscopy in speed and portability. Challenges remain in selectivity against interferents, long-term stability, and regulatory validation for clinical or industrial use. Recent advances emphasise hybrid nanomaterials (e.g., Au-GQD hybrids, MXenes, or carbon-metal composites) for multifunctional sensing and enzyme-free aptasensors, expanding utility in precision medicine and biopharmaceuticals.[12]
CHALLENGES AND LIMITATIONS
8.1. Lack of Standardisation in Nanomaterial Synthesis and Functionalization
The poor standardisation in nanoparticle synthesis, size control, morphology, surface chemistry, and functionalization protocols is one of the main obstacles in biosensor fabrication. Small variations in precursor concentration, pH, temperature, and reaction time can lead to significant differences in nanoparticle physicochemical properties. The performance of the biosensor depends heavily on surface area, catalytic activity, and electronic conductivity; batch-to-batch variability affects sensitivity and reproducibility. The functionalization steps, such as antibody immobilisation, aptamer binding, or polymer coating, are often not uniform, resulting in unstable signal responses. [14].
8.2. Device-to-Device Variations
Nanomaterial biosensors often show excellent sensitivity in laboratory-scale prototypes, but their reproducibility remains a major problem. Due to differences in electrode preparation (drop casting, electrodeposition, spin coating), thickness of nanomaterial films, nonuniform dispersion, and agglomeration, there will be variations in the device. For electrochemical biosensors, even small changes in nanomaterial loading can alter electron transfer kinetics and affect charge transfer resistance. It severely limits their applicability in routine clinical diagnosis, where repeatability is mandatory [13].
8.3. Nanomaterial Aggregation and Stability Problems
Metallic nanoparticles and carbon-based nanostructures may undergo aggregation, oxidation, or surface restructuring during storage. It affects their electroactive surface area and catalytic properties, leading to signal drift and decreased sensitivity. Aggregation results in reduced availability of active binding sites for biomolecule immobilisation and also alters optical properties in plasmonic biosensors. For clinical applications, biosensors must maintain stability under varying conditions such as humidity, temperature fluctuations, and long-term shelf storage [1].
8.4. Surface Fouling and Biofouling in Complex Biological Samples
An important limitation in clinical diagnosis is the reduced biosensor performance in real biological fluids such as serum, saliva, plasma, urine, or whole blood. These samples contain proteins, lipids, salts, metabolites, and cells that may adsorb onto nanomaterial-modified electrodes, causing biofouling. This results in reduced active binding sites, decreased conductivity, and increased background noise.[12,15]
8.5. Non-Specific Binding and Cross-Reactivity
Nanomaterials possess high surface energy and large surface area, which enhance sensitivity but also increases the probability of non-specific interactions. In immunosensors, non-specific binding of serum proteins (albumin, globulins) can generate background signals. In aptamer-based systems, cross-reactivity with structurally similar molecules may reduce specificity. This is a major limitation in clinical diagnostics, especially for cancer biomarkers, where closely related proteins coexist.
8.6. Immobilisation of Biorecognition Elements
The biosensor performance depends on the effective immobilisation of biomolecules such as antibodies, enzymes, and aptamers. But improper immobilisation can cause denaturation, reduced binding affinity, poor orientation, and loss of activity. Random immobilisation of antibodies may block antigen-binding sites, reducing sensitivity. Additionally, enzymes immobilised on nanomaterial surfaces may lose catalytic activity due to pH microenvironment changes, conformational instability, and nanoparticle surface interactions. [6,12]
8.7. Regulatory Approval and Clinical Validation
A major limitation is the translation of the biosensor into clinical validation. Most nanomaterial-based biosensors are tested using spiked samples rather than real patient samples. Clinical translation requires validation in terms of sensitivity, specificity, stability, precision, and inter-laboratory reproducibility. Moreover, regulatory agencies require strict quality assurance and biosafety evaluation, which is difficult due to the complex nature of nanomaterials. [2].
FUTURE TRENDS
Future trends in nanomaterial-assisted biosensors are strongly focused on improving real-time clinical applicability, portability, and intelligent data processing. Major advancements are expected in wearable and flexible biosensors capable of continuous monitoring of biomarkers in sweat, saliva, tears, and interstitial fluid, which can support personalised healthcare and early disease screening. In addition, microfluidic lab-on-a-chip and point-of-care diagnostic platforms integrated with nanomaterials will enable rapid, low-volume, and multiplex detection of disease biomarkers, making diagnostics more accessible in resource-limited settings. Emerging approaches such as nanozyme-based biosensors will provide enhanced stability compared to enzyme-based systems, while hybrid nanocomposites (MOFs, MXenes, quantum dots, graphene-based materials) will further strengthen signal amplification and ultra-low detection limits. Moreover, integration with AI and machine learning algorithms will allow automated signal interpretation, improved accuracy, and predictive disease monitoring, thereby enhancing applications in both clinical diagnostics and pharmaceutical drug screening.
CONCLUSION
Nanomaterial-assisted biosensors represent a transformative analytical technology in clinical diagnosis and pharmaceutical research due to their exceptional sensitivity, rapid response, miniaturisation capability, and compatibility with multiple sensing mechanisms. They have demonstrated significant potential in early disease detection, cancer biomarker analysis, infectious disease monitoring, therapeutic drug monitoring, and pharmaceutical screening applications. However, their widespread clinical translation remains limited by challenges such as nanomaterial instability, aggregation, biofouling, nonspecific binding, toxicity concerns, poor reproducibility, fabrication complexity, and lack of standardised regulatory frameworks. Continued research addressing these limitations through stable nanomaterial design, antifouling surface engineering, scalable fabrication methods, and large-scale clinical validation will be essential for commercialisation. Overall, future developments integrating smart digital healthcare tools, AI-based analysis, and multiplex point-of-care platforms are expected to expand the real-world implementation of nanomaterial-assisted biosensors in personalised medicine and advanced pharmaceutical development.
REFERENCES
Ancy L. Raj*, Reshmi Krishna A., Nanomaterial-Assisted Biosensors for Clinical Diagnosis and Therapeutic Drug Monitoring: Recent Developments and Challenges, Int. J. of Pharm. Sci., 2026, Vol 4, Issue 5, 454-469. https://doi.org/10.5281/zenodo.20008375
10.5281/zenodo.20008375
