HISTOLOGICAL, IMMUNOLOGICAL, AND BIOCHEMICAL RESPONSES TO SUBCUTANEOUS INJECTION OF A COMBINED HYDROGEL SCAFFOLD DESIGNED FOR DENTAL CANALS IN MICE

Biocompatibility does not mean the absolute lack of cytotoxicity.  If the implant material performs its function in the body and keeps the interaction between the material and the cell in the body and the organ maintains its normal function, in a way that the general reaction of the body is normal, then we can say the material is biocompatible.  The aim of this study was to evaluate the histological, immunological, and biochemical effects of collagen + PCL-PEG-PCL, gelatin + PCL-PEG-PCL, and alginate + PCL-PEG-PCL in mice after 30 days of subcutaneous injection.

The scaffolds were prepared by freeze-thinning and characterized using FTIR methods. A 500 μl hydrogel scaffold was injected into the dorsal flank region of a Swiss CD1 mouse. Animals were divided into control, collagen + PCL-PEG-PCL, gelatin + PCL-PEG-PCL, and alginate + PCL-PEG-PCL groups. The mice were euthanized after 30 days to investigate the biocompatibility of the scaffold with the use of antidiabetic drugs. Skin, liver, and kidney were sampled for histopathological investigation, gene expression, and enzyme expression.

In this study, a hybrid hydrogel scaffold was well-constructed and characterized. The ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT) can distinguish liver damage from other possibilities. In the enzymatic study, the ratio of AST to ALT in the alginate + PCL-PEG-PCL group was higher than the others (2.9 times more than that of the control group). Despite the differences between the groups (blood biochemical analysis), no significant differences were observed in the enzymatic study between the groups. In the present study, in the control and collagen + PCL-PEG-PCL groups, the expression level of interleukin 10 gene was four times lower than the alginate + PCL-PEG-PCL and gelatin + PCL-PEG-PCL groups, and the findings showed significant differences (p <0.001). SOD, CAT, and CD31 genes in the PCL-PEG-PCL + alginate group showed 10.8, 3.3, and 3.5 times more expression than the beta-actin gene, respectively, and demonstrated significant differences compared to the other groups (p <0.001). In histopathological examination of external examination and macroscopic examination of organs, there was no indication of systemic complications such as shock, septicemia, toxemia, or extensive inflammatory reactions in any of the groups.

According to the results of this study, it can be concluded that the combination scaffold of collagen + PCL-PEG-PCL has fewer complications than other groups. The scaffold (collagen + PCL-PEG-PCL) is likely to be biocompatible and has the potential for future studies to transfer the drug, cell and growth factors and it can be used as a suitable scaffold for tissue engineering (skin and bone).