Application of sodium citrate to modify collagen hydrogel biofunctional properties: experimental study findings

INTRODUCTION. Rapid destruction of materials and structures, loss of mechanical strength, deformation of architecture and shape are factors limiting the use of collagen biomaterials in regenerative medicine and tissue engineering. One of the ways to increase the strength and resistance of hydrogel biomaterials to biodegradation is to introduce additional chemical crosslinks into their composition, such as tricarboxylic acids (citric acid). However, the use of acids can provoke the death of cells in contact with the hydrogel biomaterial, which was confirmed earlier. One possible solution to this problem could be the replacement of citric acid with its salt — sodium citrate. AIM. To evaluate the effect of sodium citrate on the structural and mechanical properties of collagen hydrogel and its biocompatibility with human skin fibroblasts. MATERIALS AND METHODS. Listed below are the reagents and materials that were used in the present study: denatured collagen type I from First Alive Collagen (Russia), 80 mM sodium citrate solution. In order to achieve thermal stabilization, the hydrogels were subjected to a drying process at a temperature of 80 °C for a duration of 12 hours, then the resulting xerogels were additionally kept at 150 °C for 16 hours. The intensity of biodegradation was assessed in vitro using a TX-700 texture analyzer. The assessment of biocompatibility was conducted through direct contact using human fibroblasts (HdFb d281) obtained from the cell culture bank “Cell Culture Collection” of the Shared Use Center of the Koltzov Institute of Developmental Biology of the Russian Academy of Sciences. RESULTS. Evaluation of the intensity of hydrogel biodegradation in vitro showed that the introduction of citric acid into the collagen solution increases the resistance of the formed hydrogel to biodegradation by five times, the strength of the hydrogel increases from 7 ± 3 to 35 ± 6 kPa. It was found that sodium citrate does not affect the sorption properties of the xerogel, the amount of sorbed moisture is 3.8 ± 0.7 g, which is comparable to the original xerogel. It was revealed that the modified form of the hydrogel does not affect the proliferative activity and cell growth rate of human fibroblasts. After 48 hours of co-incubation, the number of cells increases by 70 %, which is comparable to both the control and the original gel. It was found that the surface of the hydrogel modified with sodium citrate maintains cellular adhesion and proliferative activity of fibroblasts DISCUSSION. The results of the study complement the literature data and demonstrate the potential of using citric acid salt to strengthen the hydrogel framework of collagen polypeptide chains and increase its resistance to biodegradation. The use of sodium citrate can be considered as a possible solution to the problem of standardizing the biological properties of collagen hydrogels. CONCLUSION. Thus, the use of sodium citrate in collagen hydrogels can be an effective way to increase the resistance of tissue-engineered structures to biodegradation. The results obtained can be used in the creation of medical biomaterials.