Abstract

Treatment of articular cartilage lesions remains an important challenge. Frequently the bone located below the cartilage is also damaged, resulting in defects known as osteochondral lesions. Tissue engineering has emerged as a potential approach to treat cartilage and osteochondral defects. The principal challenge of osteochondral tissue engineering is to create a scaffold with potential to regenerate both cartilage and the subchondral bone involved, considering the intrinsic properties of each tissue. Recent nanocomposites based on the incorporation of nanoscale fillers into polymer matrix have shown promising results for the treatment of osteochondral defects. In this present study, it was performed using the recently developed methodologies (electrodeposition and immersion in simulated body fluid) to obtain porous superhydrophilic poly(d,l-lactic acid)/vertically aligned carbon nanotubes/nanohydroxyapatite (PDLLA/VACNT-O:nHAp) nanocomposite scaffolds, to analyze cell behavior and gene expression of chondrocytes, and then assess the applicability of this nanobiomaterial for osteochondral regenerative medicine. The results demonstrate that PDLLA/VACNT-O:nHAp nanocomposite supports chondrocytes adhesion and decreases type I Collagen mRNA expression. Therefore, these findings suggest the possibility of novel nanobiomaterial as a scaffold for osteochondral tissue engineering applications.

Stereolithography technology associated with the employment of photocrosslinkable, biocompatible, and bioactive hydrogels have been widely used. This method enables 3D microfabrication from images created by computer programs and allows researchers to design various complex models for tissue engineering applications. This study presents a simple and fast home-made stereolithography system developed to print layer-by-layer structures. Polyethylene glycol diacrylate (PEGDA) and gelatin methacryloyl (GelMA) hydrogels were employed as the photocrosslinkable polymers in various concentrations. Three-dimensional (3D) constructions were obtained by using the stereolithography technique assembled from a commercial projector, which emphasizes the low cost and efficiency of the technique. Lithium phenyl-2,4,6-trimethylbenzoyl phosphonate (LAP) was used as a photoinitiator, and a 404 nm laser source was used to promote the crosslinking. Three-dimensional and vascularized structures with more than 5 layers and resolutions between 42 and 83 µm were printed. The 3D printed complex structures highlight the potential of this low-cost stereolithography technique as a great tool in tissue engineering studies, as an alternative to bioprint miniaturized models, simulate vital and pathological functions, and even for analyzing the actions of drugs in the human body.

Poly (lactic acid) (PLA) has been increasingly used in cutaneous tissue engineering due to its low cost, ease of handling, biodegradability, and biocompatibility, as well as its ability to form composites. However, these polymers possess a structure with nanoporous that mimic the cellular environment. In this study, nanocomposites are prepared using PLA and titanium dioxide (TiO 2) (10 and 35%-w/w) nanoparticles that also function as an active anti-scarring agent. The nanocomposites were prepared using an electrospinning technique. Three different solutions were prepared as follows: PLA, 10% PLA/TiO 2 , and 35% PLA/TiO 2 (w/w%). Electrospun PLA and PLA/TiO 2 nanocomposites were characterized morphologically, structurally, and chemically using electron scanning microscopy, transmission electron microscopy, goniometry, and X-ray diffraction. L929 fibroblast cells were used for in vitro tests. The cytotoxic effect was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Versicam (VCAN), biglicam (BIG), interleukin-6 (IL6), interleukin-10 (IL-10), and type-1 collagen (COL1A1) genes were evaluated by RT-qPCR. In vivo tests using Wistar rats were conducted for up to 15 days. Nanofibrous fibers were obtained for all groups that did not contain residual solvents. No cytotoxic effects were observed for up to 168 h. The genes expressed showed the highest values of versican and collagen-1 (p < 0.05) for PLA/TiO 2 nanocomposite scaffolds when compared to the control group (cells). Histological images showed that PLA at 10 and 35% w/w led to a discrete inflammatory infiltration and expression of many newly formed vessels, indicating increased metabolic activity of this tissue. To summarize, this study supported the potential of PLA/TiO 2 nanocomposites ability to reduce cutaneous scarring in scaffolds.

Here, butylene adipate-co-terephthalate/polypyrrole with nanohydroxyapatite (PBAT/PPy/nHAp) scaffolds were fabricated and characterized. The electrospinning process was carried out using 12 kV, a needle of 23 G, an infusion pump set at 0.3 mL/h, and 10 cm of distance. Afterwards, nHAp was directly electrodeposited onto PBAT/PPy scaffolds using a classical three-electrode apparatus. For in vivo assays (comet assay, acute and chronic micronucleus), 60 male albino Wistar rats with 4 groups were used in each test (n = 5): PBAT/PPy; PBAT/PPy/nHAp; positive control (cyclophosphamide); and the negative control (distilled water). Peripheral blood samples were collected from the animals to perform the comet test after 4 h (for damage) and 24 h (for repair). In the comet test, it was shown that the scaffolds did not induce damage to the % DNA tail and neither for tail length. After the end of 48 h (for acute micronucleus) and 72 h (for chronic micronucleus), bone marrow was collected from each rat to perform the micronucleus test. All of the produced scaffolds did not present genotoxic effects, providing strong evidence for the biological application of PBAT/PPy/nHAp scaffolds.