Innovative Horizons in Buccal Patches: Advanced Strategies for Sustained Mucosal Drug Delivery – A Comprehensive Review

Buccal patches represent a cutting-edge non-invasive platform for sustained drug release, leveraging the buccal mucosa's rich vascularity to bypass hepatic first-pass metabolism and achieve enhanced bioavailability. This review delves into their formulation intricacies, polymer innovations, fabrication techniques, and emerging technologies poised to redefine therapeutic outcomes in chronic disease management. (1,2)The buccal route exploits the oral mucosa's permeability for systemic drug delivery, with patches providing a matrix for prolonged adhesion and release.Buccal patches adhere to the buccal mucosa, facilitating direct absorption into systemic circulation while avoiding acidic degradation and enzymatic breakdown in the GI tract. Their thin, flexible design ensures comfort, with polymers forming a gel layer upon hydration for controlled diffusion. Historical evolution traces from early adhesive tablets to modern bilayered patches, driven by needs for drugs like peptides prone to oral instability. (3,4)Anatomy of buccal mucosa includes stratified squamous epithelium, lamina propria, and submucosa, with permeability influenced by keratinization and blood flow (approximately 20-30μm thickness). Drug transport occurs via paracellular (hydrophilic drugs) or transcellular (lipophilic) paths, governed by partition coefficient and molecular weight (<500 Da ideal). Factors like saliva turnover (0.5-1.5 mL/min) and masticatory movement pose challenges, mitigated by mucoadhesive strength >0.5 N/cm². (5,6)Physicochemical requirements demand neutral pH (6.2-7.4) to prevent irritation, uniform thickness (0.1-1 mm), and swelling index (50-200%) for intimate contact. Backing layers (e.g., ethyl cellulose) prevent saliva washout, enabling unidirectional release. Clinical relevance spans hypertension (atenolol patches sustaining 24h release) to pain management, with bioavailability up to 80% vs. 20-30% oral.(7,8) Innovations focus on taste-masking via ion-exchange resins and permeation enhancers like chitosan for flux enhancement (2-5-fold). Regulatory aspects per FDA emphasize stability (6-24 months at 40°C/75% RH) and bioequivalence via porcine mucosa models. This introduction sets the stage for deeper exploration, highlighting buccal patches' role in personalized medicine amid rising chronic conditions.(7)

• Classification of Buccal Patches

Buccal patches are categorized by structure, release direction, and function to suit specific drug delivery needs like sustained release. Here's a clear classification chart in table form, drawn from established types in pharmaceutical literature. (9)

Table no. 01- Classification of buccal patches(10–13)

5. METHODS FOR PATCH PREPARATION

Buccal patches are fabricated using diverse methods tailored for sustained drug release, with solvent casting being the gold standard for lab-scale thesis work due to its simplicity and reproducibility. (14,15)

• Solvent Casting Technique

The cornerstone method involves dissolving polymers like HPMC K4M (5-20% w/v) and Carbopol 934P (1-5%) in water-ethanol (50:50 v/v), followed by drug addition (e.g., 50 mg atenolol), plasticizer (PEG 400, 20-40% w/w), and permeation enhancers (chitosan 1-2%). The gel is degassed, cast on Petri dishes (10-40 mL over 50 cm² for 0.2-0.5 mm thickness), and dried at 45°C for 24-48h. Backing layers (ethyl cellulose 5% in acetone: isopropanol) are pre-cast for unidirectional release. Yields uniform patches (CV <5%) with 85-95% entrapment, ideal for 24h zero-order kinetics via hydrated gel layer diffusion (Fick's law: J = -D dc/dx). Scale-up challenges include residual solvent (<50 ppm ICH Q3C), addressed by vacuum drying. Variations: Bilayer casting (medicated gel over backing) or multi-nozzle for gradients. (15–17)

• Hot-Melt Extrusion (HME)

Solvent-free, continuous process melting polymers (Eudragit RLPO, 80-150°C) with drug (losartan 5-10%) and plasticizer (20%), extruded through 0.5 mm die at 5-20 rpm screw speed. Creates amorphous solid dispersions boosting solubility 3-5x for BCS Class II drugs. Advantages: High throughput (kg/h), no drying step; drawbacks: Thermal degradation risk (mitigated <140°C). Post-extrusion calendering yields 0.1-0.3 mm films slit to patches. Recent 2025 studies integrate twin-screw for better mixing (torque 10-20 Nm).(16,18)

• Electrospinning

Polymer solution (PVA 10% w/v in water) electrospun at 15 kV, 15 cm distance, 1 mL/h flow rate into nanofibers (100-500 nm diameter). Nanoscale porosity (70-90%) enhances surface area 1000x, accelerating initial burst then sustained release (80% in 12h). Ideal for peptides; collectors rotate for aligned fibers boosting tensile strength 2-4x. Lab setup: Syringe pump, high-voltage supply; scalable via needleless emitters.(18,19)

• 3D Printing

Fused deposition modeling (FDM): Filaments (PCL: HPMC 70:30) printed layer-by-layer (0.1 mm resolution) for personalized dosing (e.g., patient-specific losartan gradients). Semi-solid extrusion uses gels at 4°C. Enables multilayers (drug core + mucoadhesive shell). Resolution: 50-200μm; infill 20-50% controls porosity/release. Thesis advantage: On-demand prototypes via CAD designs.(18)

• Other Methods (18)

• Direct Milling/Compression: Powders kneaded, calendered without solvent; fast for heat-stable drugs but poor uniformity.
• Freeze-Drying: Polymer-drug solutions frozen (-80°C), lyophilized for porous matrices (rapid hydration).
• Spray Drying: Atomized into thin films (20-50 μm); high-speed but nozzle clogging risk.

Table No. 02- Method Aspects(15,18)

5. POLYMERS AND DRUGS IN BUCCAL PATCHES

• Polymers:(8,15,20)

Buccal patches rely on mucoadhesive polymers to ensure adhesion to the buccal mucosa, control drug release, and form flexible films suitable for sustained delivery. Common polymers are selected for biocompatibility, swelling ability, and erosion profiles, often combined for synergy in thesis formulations.

• Natural Polymers

These biocompatible options provide good mucoadhesion via hydrogen bonding and are cost-effective for lab-scale buccal patches.

• Chitosan: Derived from chitin; enhances permeation (2-5x flux increase) and mucoadhesion (force ~1-2 N/cm²); used at 1-3% w/v for pH-sensitive swelling.
• Sodium Alginate: Forms gels with Ca²?; swelling index 100-300%; ideal for matrix patches (2-5%) in combination with HPMC.
• Sodium Carboxymethyl Cellulose (NaCMC): High viscosity; rapid hydration; 1-4% for quick-dissolving types.
• Xanthan Gum/Guar Gum: Thickening agents; synergistic with synthetics for sustained release over 12h.

• Synthetic Polymers

These offer precise control, pH-sensitivity, and film-forming properties essential for unidirectional sustained-release patches.

• Hydroxypropyl Methylcellulose (HPMC): Most common (K4M, K15M, K100M grades, 5-20% w/v); viscous gel layer for diffusion control (n=0.5-0.89 Korsmeyer-Peppas); folding endurance >300.
• Carbopol (934P, 974P): Cross-linked polyacrylic acid; strong mucoadhesion (>2 N/cm² at pH 6-7); 1-5% for bilayered designs.
• Polyvinyl Alcohol (PVA): Film-former; elastic patches; combined with HPMC (2:1 ratio).
• Eudragit (RL100, RSPO): pH-independent; insoluble matrices for zero-order release; 3-10% with plasticizers.

Table No. 03- Key Comparison Table Natural Polymer Vs Synthetic Polymer

• Backing Layer Polymers

Impermeable layers prevent saliva washout in unidirectional patches.

• Ethyl Cellulose (EC): Hydrophobic; 4-6% in organic solvents for 0.05 mm films.
• Polyvinylpyrrolidone (PVP-K30): Soluble binder; 2-5% aids uniformity.

Table no. 04-Polymer Combinations Table

Synthetic and natural polymers both serve critical roles in buccal patch formulations for sustained drug release, but they differ in biocompatibility, cost, and performance consistency. Natural polymers excel in safety and sustainability, while synthetics provide superior control—often used in combination for optimal thesis formulations.

• Drugs:(21)

Drug selection for buccal patches prioritizes physicochemical properties ensuring efficient mucosal permeation and sustained release, bypassing first-pass metabolism.

Additional factors: High aqueous solubility (>1 mg/mL) for uniform loading, non-irritant at pH 6.2-7.4, and stability in saliva (pH 6.8, enzymes like amylase). Drugs needing rapid onset or chronic therapy benefit most, with permeation enhancers integrable for flux enhancement.

Table no. 05- Ideal drugs criteria(22)

Drug release from buccal patches primarily follows diffusion-controlled, swelling/erosion, or hybrid mechanisms, tailored for sustained delivery over 8-24 hours via the buccal mucosa.

Diffusion-Controlled Release

The dominant mechanism where drug diffuses through a hydrated polymer gel layer (e.g., HPMC matrix) following Fickian diffusion (Higuchi model: Q=kt

Swelling/Erosion Mechanism

Hydrophilic polymers (Carbopol, NaCMC) imbibe saliva, swell (index 100-300%), forming porous channels for drug elution; critical gel concentration (CCGC) determines erosion rate. Non-Fickian (anomalous) transport (n=0.5-0.89 Korsmeyer-Peppas) common in chitosan blends, balancing hydration and polymer chain relaxation. 8-12h biphasic release profile.

Other Mechanisms

• Dissolution: Quick-dissolving patches with PVP disintegrate rapidly (<30s).
• Osmotic Pressure: Reservoir patches with semi-permeable membranes.
  Ex vivo porcine mucosa studies confirm >85% correlation with in vivo flux.

5. PATCH PREPARATION(23)

Figure no. 01 Step by Step Formulation Process of Buccal Patches

Table no. 06 Advantages and Drawbacks of buccal patches(1,23)

Applications

• Systemic: Hypertension (losartan patches), hormone therapy.
• Local: Aphthous ulcers, candidiasis.
• Vaccines/peptides: Insulin buccal delivery (20% bioavailability).

5. NEW FUTURE TRENDS IN BUCCAL PATCH TECHNOLOGIES:

Future trends in buccal patch technology emphasize bioinspired designs, smart materials, and personalized manufacturing to enhance peptide delivery and patient compliance by 2030. Innovations like octopus-sucker suction patches boost bioavailability 10x for macromolecules via mechanical stretching and enhancers, while mussel-inspired films achieve 38 kPa wet adhesion for oral mucositis.

• Bioinspired and Smart Patches(24)

Octopus-inspired suction cups thin mucosa 60-90%, enabling 14.6% teriparatide bioavailability in dogs—painless alternative to injections. Mussel-mimetic polydopamine nanoparticles improve mucus penetration 3.5x, accelerating wound closure 6x. Biodegradable versions from sustainable polymers address eco-concerns.

Octopus-sucker-inspired patches exemplify mechanical enhancement for transbuccal peptide delivery, as seen in prototypes with dual-layer structures.?

Figure no. 02- Bioinspired and Smart Patches