Chitosan-Entrapped TiO2 Nanoparticles Synthesized Using Calendula officinalis Flower Extract — Photophysical Characterization, Biocompatibility, and Textile Dye Remediation
Summary: Published March 19, 2026 in Polymers (MDPI), this study from the Medical Bionanotechnology Laboratory, Saveetha Medical College and Hospital, SIMATS (Chennai, India), led by Koyeli Girigoswami, reports the green synthesis and characterisation of chitosan-entrapped TiO2 nanoparticles produced using dried Calendula officinalis (pot marigold) flower extract as a reducing and stabilising agent — resulting in a biocompatible nanocomposite (CTS-TiO2-CO) evaluated for photocatalytic textile dye remediation. Though primarily an environmental materials science study, this work carries relevance to wound care through three converging elements: chitosan is one of the most widely used polymers in wound dressings due to its biodegradability, biocompatibility, and film-forming capacity; Calendula officinalis has established wound-healing, anti-inflammatory, and antimicrobial properties (containing saponins, tannins, flavonoids, and furanoeudesma-1,3-diene); and TiO2-based antimicrobial nanoparticles have been investigated in the context of wound infection management and antimicrobial photocatalytic therapies. The nanocomposite was synthesised via a sol-gel method, producing crystalline anatase TiO2 nanoparticles (105–114 nm SEM diameter, spherical) that were then entrapped in chitosan, yielding a flower-shaped nanocomposite (326 nm SEM diameter, 490 nm hydrodynamic diameter, zeta potential +36 mV). The chitosan coating increased stability and reduced aggregation versus uncoated CO-TiO2. In vitro biocompatibility: >82% Chinese hamster lung fibroblast (V79) viability at 100 μg/mL. In vivo biocompatibility: 85% zebrafish embryo hatchability at 50 μg/mL, with no developmental abnormalities observed. Photocatalytic activity against crystal violet textile dye reached 26.76% degradation at 1 h, 52.02% at 2 h, and 69.19% at 4 h of sunlight exposure. GC-MS analysis identified 2-Formylhistamine as the dominant phytochemical in the CO extract (34.79%), proposed to facilitate metal ion bioreduction and nanoparticle capping during synthesis. The authors note that visible-light absorption range and dye degradation efficiency could be further improved by metal or non-metal doping, and that reusability cycling studies are needed before real-world remediation deployment.
Key Highlights:
- Green synthesis rationale: Calendula officinalis dried flower extract (containing flavonoids, saponins, tannins, coumarins, and 2-Formylhistamine as dominant bioactive) replaces toxic chemical reducing agents — producing biocompatible crystalline anatase TiO2 nanoparticles (105–114 nm) via a sustainable sol-gel approach
- Chitosan entrapment: chitosan coating (0.025%, pH 7.2) significantly reduced aggregation, increased hydrodynamic stability (zeta potential +36 mV), and enhanced biocompatibility versus uncoated TiO2 — key advantages for any potential biological or wound-adjacent application
- Biocompatibility profile: >82% fibroblast (V79) viability at 100 μg/mL in MTT assay; 85% zebrafish embryo hatchability at 50 μg/mL with no observed morphological abnormalities — supporting a low-toxicity safety profile up to tested doses
- Photocatalytic dye degradation: 69.19% crystal violet degradation after 4 hours of sunlight exposure; mechanism involves UV/visible-light generation of electron-hole pairs, producing •OH and O2•− radicals that degrade the dye chromophore via N-demethylation and oxidative ring-opening
- Wound care material context: chitosan-based nanocomposites incorporating antimicrobial metal oxide nanoparticles (TiO2, ZnO, CeO2) are an active area of wound dressing research; Calendula officinalis extract has documented anti-inflammatory, wound-healing, and antimicrobial properties — making this synthesis strategy potentially transferable to antimicrobial wound dressing platforms
- Limitations: visible-light photocatalytic efficiency could be improved with doping; reusability cycles not yet evaluated; dye degradation tested with crystal violet only; toxicity profiled at limited doses; wound-specific antimicrobial testing not conducted in this study
Keywords: chitosan nanoparticle wound dressing, TiO2 antimicrobial wound, Calendula officinalis wound healing, green synthesis nanocomposite biocompatible, photocatalytic antimicrobial wound care, chitosan polymer wound healing
Sushmitha Sundarraj, Sridhanya Mysore Shreethar, Nivitha Shri Chandrasekaran, Koyeli Girigoswami