**Background:** Chitosan is a polysaccharide derived from chitin found in crustacean exoskeletons, insect cuticles, and fungal cell walls. It is produced via chemical or biological methods involving demineralization, deproteinization, and deacetylation. Chemical methods are cheaper and produce higher yields with greater degrees of deacetylation, while biological methods may generate chitosan with superior mechanical properties. Chitosan possesses key advantages — biocompatibility, biodegradability, and antimicrobial activity — but is poorly soluble in alkaline and neutral aqueous solutions, has inadequate mechanical properties, and can exhibit burst drug release. Hydroxy- and amino-functional groups allow chemical modifications such as carboxyalkylation, sulphonation, and acetylation, which improve solubility, regenerative properties, and drug-delivery capabilities. Chitosan can be combined with natural polymers (gelatin, hyaluronic acid, alginate, collagen, silk fibroin) or synthetic polymers (polyvinyl alcohol, polypyrrole, polycaprolactone, polyvinylpyrrolidone) to enhance its properties. Formulations include nanoparticles, nanofibers, scaffolds, hydrogels, membranes, and films, fabricated via ionic gelation, solvent evaporation, cross-linking, freeze-drying, and electrospinning.
**Methods:** This is a narrative review summarizing recent experimental studies (both in vitro and in vivo) on chitosan-based biomaterials for tissue regeneration. The review covers bone, cartilage, dental, skin, cardiac, and nervous tissue applications, drawing from published research on scaffold, hydrogel, membrane, and nanoparticle formulations. Evidence is drawn from animal models including rats, mice, rabbits, dogs, and zebrafish, as well as human cell lines and stem cell cultures.
**Key Results:** *Bone regeneration:* Composite chitosan scaffolds delivering BMP2 and magnesium ions achieved complete filling of rat calvarial bone defects with woven trabecular bone. Graphene-oxide-loaded glycol chitosan/hyaluronic acid injectable hydrogel induced complete defect closure in rats at 4 weeks. Vancomycin-loaded thermosensitive chitosan/glycerol phosphate hydrogel sustained drug release for 26 days, eliminated S. aureus from infected osteoblasts within 2 days, and reduced bone inflammation at 8 weeks in a rabbit osteomyelitis model. Statin-loaded chitosan hydrogels promoted new bone formation within 15 days. A methacrylated glycol chitosan/montmorillonite hydrogel alone (without added cells or growth factors) induced new osteoid bone at 6 weeks in mice. Electrospun collagen-chitosan membranes achieved almost complete cranial bone healing at 8 weeks in rats, outperforming a commercial collagen membrane. *Cartilage regeneration:* Glycol chitosan/PEG hydrogel seeded with adipose-derived MSCs produced thicker regenerated cartilage that fused well with adjacent tissue. Multi-layered chitosan-gelatin scaffolds promoted hyaline cartilage formation (type 2 collagen, no type 10 collagen). Biphasic chitosan scaffolds with magnesium (cartilage layer) and copper (bone layer) ions improved both cartilage and subchondral bone regeneration. TGF-β1-loaded thiolated chitosan/carboxymethyl cellulose hydrogel achieved regenerated cartilage with uniform cell distribution. However, alginate-chitosan hydrogels alone did not produce significant regenerative response at growth plate injury sites. *Dental regeneration:* Silver-doped bioactive glass/chitosan/β-sodium glycerophosphate hydrogel significantly decreased IL-1β, IL-6, and TNF-α levels in rat pulpitis models. Fibrin-chitosan hydrogels inhibited E. faecalis growth. Chitosan hydrogel combined with photobiomodulation therapy and stem cells formed well-developed pulp-like tissue with predentin and new vessels. Simvastatin-releasing chitosan-calcium scaffolds increased odontoblastic marker expression and calcium-rich matrix deposition. Chitosan (2.5%) treatment of demineralized dentin improved bond strength by cross-linking with dental collagen. Chitosan-agarose hydrogels produced hydroxyapatite layers with microhardness values接近 natural enamel. *Skin regeneration:* Chitosan-based hydrogels achieved 100% wound area reduction versus 72.9% for gauze. Complete wound healing and epithelial reconstruction was achieved within 14 days with chitosan-PEG-dihydrocaffeic acid hydrogel. Hemolysis rates of 1.97–2.79% were reported. Sulfated chitosan increased M2 macrophage differentiation to nearly 50%. Chitosan-PEG hydrogel increased metabolic activity to ~95% and enhanced collagen/elastin production. Multilayer chitosan membranes healed 95% of wound area by day 10. Chitosan/polyvinyl alcohol nanofibers with titanium dioxide/curcumin achieved full skin regeneration in 14 days and stopped 90% of bacterial growth within 1 hour. A topical chitosan gel showed 97.3% 'good' wound healing at 7 days versus 22.2% for placebo in a clinical trial of post-surgical wounds. *Cardiac regeneration:* Chitosan/graphene oxide scaffolds increased connexin-43 expression and electrical conductivity. Chitosan/alginate scaffolds achieved 96% porosity. Poly-pyrrole-chitosan hydrogel injected into rat myocardial infarction models shortened prolonged QRS/QT intervals and improved cardiac function. Acellular chitosan hydrogels with 24% degree of acetylation decreased fibrosis and hypertrophic stress. Chitosan hydrogel delivery of mesenchymal stem cells improved cell survival, reduced inflammation, and regenerated cardiac tissue in mouse MI models. *Nervous tissue regeneration:* Chitosan/polycaprolactone/gold nanoparticle scaffolds had pore sizes of 126 ± 20 nm and 75–80% hydrophilicity without cytotoxicity. PLLA/chitosan scaffolds increased neuroblastoma cell attachment from 78.2% to 94.3%. Chitosan/PEG scaffolds showed highest cell survival. Chitosan/collagen scaffolds reduced pore size (109.93 ± 14.48 μm) and modulated degradation without inflammation in rabbits. Chitosan-graphene oxide scaffolds (18–87 μm pores) restored locomotion in rat spinal cord injury. Chitosan scaffolds releasing nerve growth factor for 8 weeks reconnected 20 mm sciatic nerve defects with functional recovery at 12 weeks. Aligned chitosan nanofiber hydrogel repaired 15 mm nerve defects via PI3K/AKT signaling. Chitosan-HA hydrogels sustained growth factor release for >6 weeks and repaired 10 mm sciatic defects.
**Clinical Implications:** Chitosan is cost-effective (animal-derived: $10–1,000/kg; fungal: $50–5,000/kg) and FDA-approved as a food additive. Over 100 clinical trials are underway. However, FDA approval for biomedical use is currently limited to wound dressings and nerve conduits; a chitosan scaffold for cartilage repair is approved in Europe and Canada. Regulatory challenges include source-dependent impurities (heavy metals, bacterial/protein contamination), allergenic tropomyosin in animal-derived chitosan, and variability in deacetylation degree (70–90%). Fungal chitosan may resolve purity and consistency issues. Successful clinical translation requires thorough material characterization, safety profiling, and standardization from manufacturers.