Cellulase-assisted platelet-rich plasma release from nanofibrillated cellulose hydrogel enhances wound healing.

Platelet-rich plasma (PRP) is a source of growth factors, which are implicated in active tissue regeneration. However, after transplantation the efficacy of these bioactive compounds is often diminished due to rapid degradation and untargeted localization. For this reason, we evaluated the potential of nanofibrillated cellulose (NFC) hydrogel as a PRP carrier. NFC hydrogel is an animal-free biomaterial that, when doped with cellulase, can assist the release of PRP in a wound site. In this study, we examined the effects of 0.5% (m/v) NFC hydrogel formulations, including PRP and cellulase, on the migration and proliferation of skin cells via an in vitro scratch wound model. The suitability of the 0.8% NFC hydrogel formulations for accelerated wound healing and PRP carrying was studied in vitro in diffusion studies and in vivo in a full-thickness excisional wound model in SKH1 mice. None of the NFC hydrogel formulations with or without PRP and cellulase disturbed the normal cell behavior in vitro, and cellulase was successfully used to degrade NFC. NFC hydrogel slowed fibroblast migration rate in vitro. In vivo, NFC hydrogel treatment showed significantly enhanced re-epithelialization compared to control and supported collagen deposition. In addition, angiogenesis was significantly induced via PRP release after degrading NFC hydrogel with cellulase without abnormal host reaction. This study demonstrates the potential of NFC hydrogel with cellulase as a carrier for PRP with controlled release in future skin tissue engineering applications.

Stiffness-Controlled Hydrogels for 3D Cell Culture Models.

Nanofibrillated cellulose (NFC) hydrogel is a versatile biomaterial suitable, for example, for three-dimensional (3D) cell spheroid culturing, drug delivery, and wound treatment. By freeze-drying NFC hydrogel, highly porous NFC structures can be manufactured. We freeze-dried NFC hydrogel and subsequently reconstituted the samples into a variety of concentrations of NFC fibers, which resulted in different stiffness of the material, i.e., different mechanical cues. After the successful freeze-drying and reconstitution, we showed that freeze-dried NFC hydrogel can be used for one-step 3D cell spheroid culturing of primary mesenchymal stem/stromal cells, prostate cancer cells (PC3), and hepatocellular carcinoma cells (HepG2). No difference was observed in the viability or morphology between the 3D cell spheroids cultured in the freeze-dried and reconstituted NFC hydrogel and fresh NFC hydrogel. Furthermore, the 3D cultured spheroids showed stable metabolic activity and nearly 100% viability. Finally, we applied a convolutional neural network (CNN)-based automatic nuclei segmentation approach to automatically segment individual cells of 3D cultured PC3 and HepG2 spheroids. These results provide an application to culture 3D cell spheroids more readily with the NFC hydrogel and a step towards automatization of 3D cell culturing and analysis.

Near-infrared analysis of nanofibrillated cellulose aerogel manufacturing.

Biomaterial aerogel fabrication by freeze-drying must be further improved to reduce the costs of lengthy freeze-drying cycles and to avoid the formation of spongy cryogels and collapse of the aerogel structures. Residual water content is a critical quality attribute of the freeze-dried product, which can be monitored in-line with near-infrared (NIR) spectroscopy. Predictive models of NIR have not been previously applied for biomaterials and the models were mostly focused on the prediction of only one formulation at a time. We recorded NIR spectra of different nanofibrillated cellulose (NFC) hydrogel formulations during the secondary drying and set up a partial least square regression model to predict their residual water contents. The model can be generalized to measure residual water of formulations with different NFC concentrations and the excipients, and the NFC fiber concentrations and excipients can be separated with the principal component analysis. Our results provide valuable information about the freeze-drying of biomaterials and aerogel fabrication, and how NIR spectroscopy can be utilized in the optimization of residual water content.