Mechanical and physicochemical behavior of a 3D hydrogel scaffold during cell growth and proliferation.

Some of the essential properties for cellular scaffolding are the capability to maintain the three-dimensional (3D) structure, good adhesion, and adequate elastic modulus during cell growth, migration, and proliferation. Biocompatible synthetic hydrogels are commonly used as cellular scaffolds because they can mimic the natural extracellular matrices (ECMs). However, it is possible that the physicochemical and mechanical behavior of the scaffold changes during cell proliferation and loses the scaffold properties but this is rarely monitored. In this work, the physicochemical and mechanical properties of a macroporous soft material based on poly(N-isopropyl acrylamide) (PNIPAM) have been studied during a period of 75 days at culture condition while bovine fetal fibroblasts (BFF) were grown within the matrix. The interconnected macroporous hydrogel was obtained by cryogelation at -18 °C. The swelling capacity of the scaffold was not altered during cell proliferation but changes in the mechanical properties were observed, beginning with the high elastic modulus (280 kPa) that progressively decreased until mechanical stability (40 kPa) was achieved after 20 culture days. It was observed that the matrix-cell interactions together with collagen production favor normal cellular processes such as cell morphology, adhesion, migration, and proliferation. Therefore, the observed behavior of macroporous PNIPAM as a 3D scaffold during cell growth indicates that the soft matrix is cytocompatible for a long time and preserves the suitable properties that can be applied in tissue engineering and regenerative medicine.

Cytotoxicity and bioadhesive properties of poly-N-isopropylacrylamide hydrogel.

Several hydrogel surfaces present properties that simulate the mechanical and physicochemical features of extracellular matrix (ECM), providing a platform that mimic the native cellular milieus. Poly-N-isopropylacrylamide (PNIPAM) hydrogels are receiving attention in biomedical field due to their thermosensibility and soft texture. However, more extensive biocompatibility and cellular interactions studies with cell lines are needed. Therefore, the aim of this study is focus on evaluating the biocompatibility of PNIPAM through cytotoxicity, genotoxicity, and proliferation tests in murine preadipose cells (3T3-L1), human embryonic kidney cells (HEK293) and human carcinoma-derived cells (A549) in presence of hydrogel surfaces. Bioadhesive capacity above PNIPAM surfaces was also analyzed. MTT and neutral red uptake assays shown non-cytotoxic effect of PNIPAM in the studied cell lines. Genotoxicity was evaluated by the single-cell gel electrophoresis assay, where DNA damages were not detected. [3H]-thymidine staining allowed to corroborate that cell proliferation had progressed correctly. Adopted morphologies for each cell line over PNIPAM were similar to cell growing observed on polystyrene, indicating that the surfaces favor the cell attachment during 5 days' culture. The good biocompatibility of PNIPAM surfaces make it an interesting scaffold with clinical potential in tissue regeneration engineering, and a possible adipose and kidney tissue-engineered construct.