The lack of bone grafts represents a major issue in the orthopedic field, reconstructive surgery, and dentistry. There are several bone conditions that often demand the use of grafts, such as fractures, infections, and bone cancer. The number of bone cancer cases increased in the past few decades and along with it, the need for bone grafting materials. To avoid the use of autografts and allografts there has been an increased interest towards synthetic grafts. This research aims to develop some collagen/hydroxyapatite (Coll/HAp) scaffolds cross-linked with three different agents that could be used in bone tissue engineering (BTE). These scaffolds were obtained with a freeze-drying method after the in situ formation of hydroxyapatite inside the collagen matrix. They were structurally and morphologically characterized and evaluated in terms of antimicrobial activity on E. coli and S. aureus bacterial strains. The results revealed that the scaffolds have porous structures with interconnected pores of suitable dimensions and well-distributed inorganic phases. Coll/HAp samples showed great antibacterial activity even without the use of typically used antibacterial agents. These findings allow us to conclude that these scaffolds are promising candidates for use in BTE and bone cancer treatment after the incorporation of specific antitumoral drugs.

Collagen is one of the main constituents of cosmetic formulations because of its moisturizing, regenerating, and film-forming properties. The aim of the present study was to obtain biocompatible collagen hydrolysates from Hypophthalmichthys molitrix skin, using a neutral inexpensive hydrolysis process involving low temperature (135 °C) and pressure values (315 kPa) and by using various pretreatment procedures (in order to eliminate the scales, fat, and meat). Comprehensive characterization of the hydrolysate samples confirmed their high purity, evidenced by a protein content exceeding 10%, undetected ash levels, and a pH between 6 and 7. This was further supported by optical microscopy and SEM imaging, which revealed the characteristic fibril structure. Additionally, FTIR analysis and CD spectroscopy verified a specific random coil structure and the complete absence of the triple helix characteristic of denatured collagen. EDX results confirmed the presence of C, O, N, and traces of S in all collagen hydrolysate samples. The results of the microbiological analysis for E. coli and S. aureus show either the complete absence or negligible amounts of fungi and bacteria in all hydrolysate samples, thereby demonstrating the effectiveness of the extraction process. The in vitro biocompatibility assessment established a non-cytotoxic concentration range between 1.25 mg/mL and 10 mg/mL for the tested samples, with cell viability above 70% and LDH release below 5%. Furthermore, clinical patch tests of the obtained fish collagen hydrolysates revealed no irritation reactions. Neutral hydrolysis of silver carp skin collagen hydrolysates with determined characteristics and favorable biocompatibility proves to be suitable for cosmetic applications.