In vivo biocompatibility of elderberry-enriched carboxymethyl chitosan in soft tissue and calvaria bone defects

Regeneration of soft and hard tissues remains a major challenge in periodontal and craniofacial applications, necessitating the development of multifunctional and biocompatible scaffolds. This study investigates the in vivo biocompatibility and regenerative potential of elderberry-enriched, polyethylene glycol diglycidyl ether (PEGDE)-crosslinked carboxymethyl chitosan (CMCht-E) in a rat model. Twenty-six eight-week-old female Wistar rats were randomly assigned to three experimental groups (subcutaneous, intramuscular, and calvarial; n = 7 per group). In each rat, symmetrical 5 mm defects were created, with the biomaterial implanted on one side and the contralateral side serving as the control. A sham group (n = 5) was included to account for surgical and imaging-related effects. Tissue responses were evaluated using ultrasonography, computed tomography (CT), micro-computed tomography (micro-CT), histomorphometry, and immunohistochemistry (CD68/CD163). Soft tissue healing, confirmed by both ultrasonography and histological analysis, revealed similar characteristics between the biomaterial and control sites, suggesting a regenerative response closely resembling native tissue architecture. In the calvarial group, histomorphometric assessment and micro-CT analysis demonstrated a statistically significant increase in new bone formation in the CMCht-E group compared to controls (p < 0.05). There were no significant differences in CD68 and CD163 expression between biomaterial and control groups (p > 0.05). This first in vivo study demonstrates that CMCht-E is biocompatible and supports bone and soft tissue regeneration through controlled biodegradation. These findings highlight its promise as a naturally derived biomaterial for future use in periodontal and tissue engineering applications.