Background: Chitin and chitosan are biopolymers with exceptional biocompatibility, biodegradability, and wound-healing properties. Conventionally, chitin is extracted from crustacean shells (shrimp, crab), but this source has limitations including seasonal availability, allergenic potential (shellfish allergy), and environmental concerns related to acid-alkali waste disposal. Dead adult houseflies (Musca domestica) represent an underexplored, abundant, and sustainable alternative source of chitin. Houseflies breed rapidly, and dead flies are available year-round as waste from fly rearing facilities. However, no standardized method exists for chitin and chitosan isolation from adult houseflies for wound dressing applications.

Objective: To isolate, characterize, and optimize chitin and chitosan from dead adult houseflies (Musca domestica) and evaluate their wound dressing potential.

Methods: Dead adult houseflies were collected from BMS College of Pharmacy, Tiloi, and Amethi UP India, cleaned, dried, and defatted using petroleum ether. Chitin was isolated through a three-step chemical process: (1) deproteinization using 1M NaOH at 80°C for 6 hours, (2) demineralization using 1M HCl at room temperature for 4 hours, and (3) decolorization using 0.3% sodium hypochlorite (NaOCl) for 1 hour. Chitosan was produced by deacetylation of chitin using 50% NaOH at 100°C for 4 hours. Process parameters (temperature, time, alkali concentration) were optimized using a one-factor-at-a-time approach. Isolated chitin and chitosan were characterized by: yield percentage, degree of deacetylation (DDA) by FTIR and titration, molecular weight by viscometry, solubility in 1% acetic acid, moisture content, ash content, protein residue (Kjeldahl method), and colour. Surface morphology was examined by SEM. Crystalline structure was analyzed by XRD. Thermal stability was assessed by TGA/DSC. Antimicrobial activity against S. aureus and E. coli was tested by disk diffusion. For wound dressing formulation, chitosan was dissolved in 1% acetic acid (2% w/v) and cast into films with glycerol as plasticizer (0.5% w/w). Films were crosslinked with tripolyphosphate (TPP) and characterized for thickness, tensile strength, elongation, water vapor transmission rate (WVTR), swelling ratio, biodegradation, and in vivo wound healing in Wistar rats using an excision wound model (n=6 per group): (I) control (no treatment), (II) marketed dressing (Betadine), (III) chitosan film, (IV) chitin powder. Wound contraction percentage, epithelialization time, histopathology (H&E, Masson’s trichrome), and hydroxyproline content were evaluated.

Results: The optimized isolation protocol yielded 8.4 ± 0.3% chitin and 5.2 ± 0.2% chitosan from dry housefly weight. The chitosan had a degree of deacetylation of 82.5 ± 1.2% (by FTIR) and molecular weight of 98.5 ± 4.2 kDa. Solubility in 1% acetic acid was 94.2 ± 1.5%. FTIR spectra showed characteristic amide bands confirming chitin (1652 cm⁻¹, 1620 cm⁻¹) and chitosan (1595 cm⁻¹). SEM revealed porous, fibrillar structure. XRD showed crystalline peaks at 2θ = 9.2° and 19.4° for chitin, and 10.1° and 20.2° for chitosan. TGA showed degradation onset at 280°C for chitin and 260°C for chitosan. Antimicrobial testing showed inhibition zones of 18.5 ± 1.2 mm (chitosan vs. S. aureus) and 15.2 ± 1.1 mm (vs. E. coli). Chitosan films had tensile strength 24.5 ± 1.8 MPa, elongation 32.4 ± 2.1%, WVTR 1850 ± 85 g/m²/day, swelling ratio 450 ± 25%, and biodegradation 65% in 14 days. In vivo wound healing: chitosan film group showed 98.2 ± 1.5% wound contraction by day 14 (vs. control 72.4 ± 2.8%, p<0.001), complete epithelialization at 12.4 ± 1.2 days (vs. control 18.6 ± 1.4 days, p<0.001). Histopathology showed complete re-epithelialization, collagen deposition, and neovascularization in chitosan film group. Hydroxyproline content was significantly higher in chitosan film group (48.6 ± 2.4 mg/g vs. control 24.3 ± 1.8 mg/g, p<0.001).