A 6-bromoindirubin-3'-oxime incorporated chitosan-based hydrogel scaffold for potential osteogenic differentiation: Investigation of material properties in vitro

Effective treatments for critical size bone defects remain challenging. 6-Bromoindirubin-3'-Oxime (BIO), a glycogen synthase kinase 3β inhibitor, is a promising alternative for treatment of these defects since it aids in promoting osteogenic differentiation. In this study, BIO is incorporated into a new formulation of the guanosine diphosphate cross-linked chitosan scaffold to promote osteogenic differentiation. BIO incorporation was confirmed with ¹³C NMR through a novel concentration dependent peak around 41 ppm. The rapid gelation rate was maintained along with the internal structure's stability. The 10 μM BIO dose supported the control scaffold's microstructure demonstrating a suitable porosity and a low closed pore percentage. While pore sizes of BIO incorporated scaffolds were slightly smaller, pore heterogeneity was maintained. A proof-of-concept study with C2C12 cells suggested a dose-dependent response of BIO on early stages of osteogenic differentiation within the scaffold. These results support future work to examine BIO's role on osteogenic differentiation and biomineralization of encapsulated cells in the scaffold for bone regeneration.

Construction of chitosan scaffolds with controllable microchannel for tissue engineering and regenerative medicine

Microchannels are effective means of enabling the functional performance of tissue engineering scaffolds. Chitosan, a partial deacetylation derivative of chitin, exhibiting excellent biocompatibility, has been widely used in clinical practice. However, development of chitosan scaffolds with controllable microchannels architecture remains an engineering challenge. Here, we generated chitosan scaffolds with adjustable microchannel by combining a 3D printing microfiber templates-leaching method and a freeze-drying method. We can precisely control the arrangement, diameter and density of microchannel within chitosan scaffolds. Moreover, the integrated bilayer scaffolds with the desired structural parameters in each layer were fabricated and exhibited no delamination. The flow rate and volume of the simulated fluid can be modulated by diverse channels architecture. Additionally, the microchannel structure promoted cell survival, proliferation and distribution in vitro, and improved cell and tissue ingrowth and vascular formation in vivo. This study opens a new road for constructing chitosan scaffolds, and can further extend their application scope across tissue engineering and regenerative medicine.

3D printed chitosan scaffolds: A new TiO2 support for the photocatalytic degradation of amoxicillin in water

TiO₂-supported chitosan scaffolds (TiO₂/CS) are here proposed as promising material for wastewater treatment, in particular for the removal of pharmaceutical compounds. TiO₂/CS are tested for the amoxicillin photodegradation under UV/Vis irradiation. Amoxicillin (AMX) is an antibiotic of the beta-lactam family. Due to the release of antibiotics in wastewater and their persistence in the environment, harmful effects can develop on the aquatic and terrestrial organisms. TiO₂ chitosan scaffolds with photocatalytic activity for wastewater remediation have been prepared by 3D printing using commercial P25-TiO₂. The formulation for the 3D printer was prepared by dispersion of chitosan and TiO₂ in powder form at the concentration 6% w/v and 1% w/v, respectively. The TiO₂ particles (crystalline anatase and rutile phases) embedded in the chitosan have a size of about 20 nm, like in the starting material, as verified by X-ray diffraction and Raman spectroscopy and are homogeneously distributed in the scaffold, also after repeated photocatalytic tests, as revealed by SEM-EDS. The mechanical properties of the 3D structures are suitable for the targeted application as they can be easily handled without breakage. The AMX photodegradation efficiency under light irradiation by TiO₂/CS made with scaffolds of different thicknesses (3, 5, 15 layers), was assessed in water by means of UV-Vis absorption and HPLC/UV measurements, at two different AMX:TiO₂ molar ratios: 1/100 and 1/10. The 3D printed TiO₂/CS system, even after repeated cycles, shows a high photodegradation efficiency, compared to the direct AMX photolysis. A zero-order kinetics for TiO₂ supported photodegradation was found, whereas a pseudo-first order was observed for water dispersed TiO₂. Mass spectrometry analysis revealed the presence of AMX degradates such as penilloic and penicilloic acids and diketopiperazine. The proposed 3D printed chitosan scaffolds may be used as reusable substrate for the TiO₂ photocatalytic degradation of antibiotic pollutants in wastewater.

Chitosan/hydroxyapatite (HA)/hydroxypropylmethyl cellulose (HPMC) spongy scaffolds-synthesis and evaluation as potential alveolar bone substitutes

Alveolar bone loss is associated with infections and its augmentation is a pre-requisite for the success of dental implants. In present study, we aim to develop and evaluate novel freeze dried doxycycline loaded chitosan (CS)/hydroxyapatite (HA) spongy scaffolds where hydroxypropylmethyl cellulose (HPMC) was added as a crosslinker. Scaffolds displayed compressive strength of 14MPa/cm³ and 0.34 as elastic response. The interconnected pore diameter was 41-273μm, favorably provided the template supporting cells and transport. An overall 10% degradation was seen after 14day's studies at pH 7.4 in PBS. Doxycycline hyclate, a frequently used drug to counter oral infections, demonstrated an initial burst release (6-8h), followed by a sustain release profile for the remaining 64h. CS/HA/HPMC scaffolds were nontoxic and promoted pre-osteoblast cell viability as seen with live/dead calcein staining after 24h where scaffolds with 10% and 25% HPMC by weight of scaffold had more viable cells. Scaffolds with 10%, 20% and 25% HPMC by weight of scaffold showed efficient cellular adhesion as seen in scanning electron microscopy images (day 8) indicating that pre-osteoblast cells were able to adhere well on the surface and into the porous structure via cytoplasmic extensions. Hoechst 33258 nuclear staining at day 2 and 8 indicated cell proliferation which was further supported byMTT assay at day 2, 4 and 8. Although all scaffolds supported pre-osteoblast cell viability, alkaline phosphatase (ALP) staining demonstrated that upon induction, differentiation was pronounced in case of scaffolds with 10% HMPC scaffolds. Conclusively, these materials having all the required mechanical and biological properties are potential candidates for alveolar bone regeneration.

Chitosan scaffolds induce human dental pulp stem cells to neural differentiation: potential roles for spinal cord injury therapy

Cell-based transplantation strategies hold great potential for spinal cord injury (SCI) repair. Chitosan scaffolds have therapeutic benefits for spinal cord regeneration. Human dental pulp stem cells (DPSCs) are abundant available stem cells with low immunological incompatibility and can be considered for cell replacement therapy. The purpose of this study is to investigate the role of chitosan scaffolds in the neural differentiation of DPSCs in vitro and to assess the supportive effects of chitosan scaffolds in an animal model of SCI. DPSCs were incubated with chitosan scaffolds. Cell viability and the secretion of neurotrophic factors were analyzed. DPSCs incubated with chitosan scaffolds were treated with neural differentiation medium for 14 days and then neural genes and protein markers were analyzed by Western blot and reverse transcription plus the polymerase chain reaction. Our study revealed a higher cell viability and neural differentiation in the DPSC/chitosan-scaffold group. Compared with the control group, the levels of BDNF, GDNF, b-NGF, and NT-3 were significantly increased in the DPSC/chitosan-scaffold group. The Wnt/β-catenin signaling pathway played a key role in the neural differentiation of DPSCs combined with chitosan scaffolds. Transplantation of DPSCs together with chitosan scaffolds into an SCI rat model resulted in the marked recovery of hind limb locomotor functions. Thus, chitosan scaffolds were non-cytotoxic and provided a conducive and favorable microenvironment for the survival and neural differentiation of DPSCs. Transplantation of DPSCs might therefore be a suitable candidate for treating SCI and other neuronal degenerative diseases.