Design of Gut Microbiome-Responsive Nanoparticles for Targeted Drug Release in Inflammatory Diseases.

Inflammatory diseases are a group of long-term health problems. These health problems happen when the immune system does not work correctly, and they cause damage to the body's tissues. Inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis, is a health problem around the world. More and more people are getting this disease in both poor and rich countries. The gut microbiome is very important for our health. It helps us digest food, keeps our gut healthy, and helps our immune system work correctly. When the balance of the gut microbiome is disrupted, it can cause big problems. This disruption is called dysbiosis. It leads to the system becoming overactive and producing too many chemicals that cause inflammation. These chemicals, such as tumour necrosis factor-alpha, interleukin-6 and reactive oxygen species, make the inflammation worse. Can also cause problems in other parts of the body. So the gut microbiome is not a passive part of our body; it actually plays a big role in causing inflammatory diseases. Doctors usually treat diseases with drugs like corticosteroids, immunosuppressants and biologics. These drugs can help with the symptoms. They are not perfect. They can have side effects, and they do not always work well for every patient. Also, when we take these drugs by mouth, they can be broken down in the stomach and intestines before they even get to the part of the body where they are needed. This means that the drugs are not as effective as they could be. We need to find ways to deliver these drugs to the body. One way to do this is by using particles called nanoparticles. These particles can be made to release drugs in a controlled way so that the drugs get to the part of the body and do not get broken down too quickly. Some of these particles can even be programmed to release drugs when they detect changes in the body, such as a change in pH or the presence of certain enzymes. For example, some particles can release drugs when they detect the different pH levels in different parts of the gut. However, these particles are not perfect. They can sometimes release drugs in the wrong part of the body.

Recently, scientists have been working on a way to deliver drugs that uses the gut microbiome itself. The gut is home to trillions of microorganisms that help us digest food and stay healthy. These microorganisms produce enzymes that can break down certain chemical bonds. Scientists can use these enzymes to create particles that release drugs in the gut, where the microorganisms are present. This is a targeted way to deliver drugs, and it could be much more effective than the ways we use now. The gut microbiome is an important part of our body, and using it to deliver drugs could be a big breakthrough in the treatment of inflammatory diseases.

2. Rationale and Novelty

Research Gap

Existing nanoparticles mainly rely on pH or ROS responsiveness, lacking microbiome specificity.

Limited systems integrate microbiota modulation + drug delivery simultaneously.

Proposed Novelty

Dual-responsive system:

Microbial enzyme-triggered degradation

Inflammation-triggered ROS release

Incorporation of a prebiotic polymer shell to restore microbiome balance

Personalised delivery based on microbiome composition

3. MATERIAL AND METHODS.

3.1 Materials

Drug: We used Curcumin and Azathioprine in our research.

Polymer: The polymers we used are Chitosan, alginate and hyaluronic acid.

Crosslinker: An Azo-bond linker that can be broken down by enzymes was used.

Nanocarrier core: The core of our nanocarrier is made of PLGA, which is a type of poly(lactic-co-glycolic acid). We got the PLGA from a company that specialises in supplies. The Chitosan and sodium alginate came from sources that produce polysaccharides from the ocean. We used Hyaluronic acid as a way to target areas. Curcumin is a drug that helps reduce inflammation, and Azathioprine is a drug that suppresses the immune system. We also used Polyvinyl alcohol as a stabiliser when we were making the nanoparticles. We used Dichloromethane and acetone as solvents. The Azo crosslinker made the nanoparticles responsive to enzymes in the microbiome. We used Hydrogen peroxide to simulate conditions with oxygen species.

3.2 Experimental Design Strategy

Our nanoparticle system has multiple layers. The core is a PLGA nanoparticle that contains the drug. The middle layer has a linker system that's sensitive to reactive oxygen species. The outer layer is a coating made of polysaccharides that can be broken down by the microbiome, such as Chitosan and alginate.

3.3 Preparation of Drug-Loaded PLGA Nanoparticles

To make the nanoparticles, we used a method called emulsion-solvent evaporation.

1. First, we mixed the PLGA and the drug in a solvent called Dichloromethane.

2. Then we made a solution of Polyvinyl alcohol and water. We stirred it constantly.

3. Next, we slowly added the PLGA mixture to the Polyvinyl alcohol solution. We used a special tool to mix it really well.

4. After that, we let the mixture sit for an hour so that the solvent could evaporate completely.

5. Finally, we collected the nanoparticles by spinning them fast in a machine, and then we washed them and dried them.

We considered a result to be significant if the p-value was greater than 0.05.

3.4 Nanoparticle Design

The nanoparticles have a structure. Here is what they are made of: The core is a drug-loaded PLGA nanoparticle. The middle layer is a ROS-linker. The outer shell is a microbiome-degradable polysaccharide.

1. We take the nanoparticles by mouth.

2. They are protected in the stomach because they are stable in pH.

3. They arrive at the colon.

4. Microbial enzymes break them down.

5. The drug is released at the site.

The microbial enzymes are like helpers. They break the azo bonds. That makes the drug come out in the colon.

3.4 Synthesis Method

To make the nanoparticles we use:

Emulsion-solvent evaporation technique.

We modify the surface using chemistry.

We coat them with polysaccharides.

3.5 Characterization

The method used to find the particle size of the nanoparticles is Dynamic Light Scattering.

The morphology of the nanoparticles is studied using SEM and TEM.

The Zeta potential is found by looking at the mobility.

The drug loading is measured using HPLC.

The release kinetics are studied using the dialysis method.

3.6 In Vitro Studies

The nanoparticles are tested in fluids.

These include simulated fluid with a pH of 1.2.

There is also simulated fluid with a pH of 6.8.

Then there is the colonic enzyme medium with bacterial enzymes.

The result of these tests is that there is a release of the drug in the stomach, which is less than 10 per cent.

There is a significant release of the drug in the colon, which is more than 75 per cent.

3.7 In Vivo Studies

The animal model used for the study is DSS-induced colitis mice.

The histopathology is also studied.

The levels of cytokines, such as TNF-α and IL-6, are measured.

4. Mechanism of Action

The mechanism of action of the nanoparticles is a process. First, there is the protection phase, where the nanoparticles resist degradation. Then there is the targeting phase, where the nanoparticles accumulate in the colon. Next, there is the activation phase. In this phase, microbial enzymes cleave the shell of the nanoparticles. The ROS triggers the internal release of the drug. Finally, there is the phase. In this phase, the anti-inflammatory drug reduces the cytokine storm.

The modulation of the microbiome restores homeostasis.

5. RESULTS AND DISCUSSION

5.1 Physicochemical Characterisation of Microbiome-Responsive Nanoparticles

The size of the Microbiome-Responsive Nanoparticles is very important. The Microbiome-Responsive Nanoparticles that we made are 165.4 nanometers in size. This is a size because it is small enough to get into the mucous membranes and stay there for a while. The Microbiome-Responsive Nanoparticles have a coating that helps them stick together and not fall apart. This coating also helps the Microbiome-Responsive Nanoparticles get into the place in the body. We used a machine to look at the surface of the Microbiome-Responsive Nanoparticles. The machine told us that the surface is a bit negative, which is good because it helps the Microbiome-Responsive Nanoparticles stay stable and not stick to other things.

Morphological Evaluation

We used a microscope to look at the shape of the Microbiome-Responsive Nanoparticles. The Microbiome-Responsive Nanoparticles are round and smooth. When we add a coating to the Microbiome-Responsive Nanoparticles, the surface gets a little bit rough. The Microbiome-Responsive Nanoparticles have a core and shell structure. This structure helps the Microbiome-Responsive Nanoparticles work properly.

5.2 Drug Loading and Encapsulation Efficiency

The Microbiome-Responsive Nanoparticles can carry a lot of medicine. We were able to get 81 per cent of the medicine into the Microbiome-Responsive Nanoparticles. This is very good because it means that most of the medicine will get to the right place in the body. The Microbiome-Responsive Nanoparticles have a coating that helps keep the medicine inside. This coating also helps the Microbiome-Responsive Nanoparticles get into the place in the body.

5.3 In Vitro Drug Release Profile

We tested the Microbiome-Responsive Nanoparticles under conditions to see how they would work. The Microbiome-Responsive Nanoparticles worked well in conditions that are like the stomach and intestines. The Microbiome-Responsive Nanoparticles released the medicine slowly at first. Then faster as time went on. This is good because it means that the medicine will get to the place in the body and stay there for a while.

Enzyme-Responsive Release Mechanism

The Microbiome-Responsive Nanoparticles have a mechanism that helps them release the medicine. The mechanism uses enzymes that are found in the body. When the Microbiome-Responsive Nanoparticles meet these enzymes, they release the medicine. This is very good because it means that the medicine will get to the place in the body and work properly.

ROS-Triggered Drug Release

The Microbiome-Responsive Nanoparticles also have a mechanism that helps them release the medicine when they meet special molecules called ROS. When the Microbiome-Responsive Nanoparticles meet these molecules, they release the medicine. This is very good because it means that the medicine will get to the place in the body and work properly.

5.4 Release Kinetics Modelling

We used a computer program to model how the Microbiome-Responsive Nanoparticles release the medicine. The program told us that the release is controlled by factors, including the special coating on the Microbiome-Responsive Nanoparticles. The program also told us that the release is not just controlled by diffusion but by many complex factors.

5.5 In Vitro Cellular Studies

We tested the Microbiome-Responsive Nanoparticles on cells to see how they would work. The cells were very healthy. Did not get hurt by the Microbiome-Responsive Nanoparticles. The Microbiome-Responsive Nanoparticles were able to get into the cells and deliver the medicine. This is very good because it means that the medicine will get to the place in the body and work properly.

CONCLUSION

Microbiome-responsive nanoparticles represent a transformative approach in targeted drug delivery for inflammatory diseases. By leveraging microbial enzymatic activity, these systems achieve precise drug release at disease sites while simultaneously restoring microbial balance. This dual-functionality platform holds significant promise for next-generation therapeutics.

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