Development of bioactive short fiber-reinforced printable hydrogels with tunable mechanical and osteogenic properties for bone repair.

Personalized bone-regenerative materials have attracted substantial interest in recent years. Modern clinical settings demand the use of engineered materials incorporating patient-derived cells, cytokines, antibodies, and biomarkers to enhance the process of regeneration. In this work, we formulated short microfiber-reinforced hydrogels with platelet-rich fibrin (PRF) to engineer implantable multi-material core-shell bone grafts. By employing 3D bioprinting technology, we fabricated a core-shell bone graft from a hybrid composite hydroxyapatite-coated poly(lactic acid) (PLA) fiber-reinforced methacryolyl gelatin (GelMA)/alginate hydrogel. The overall concept involves 3D bioprinting of long bone mimic microstructures that resemble a core-shell cancellous-cortical structure, with a stiffer shell and a softer core with our engineered biomaterial. We observed a significantly enhanced stiffness in the hydrogel scaffold incorporated with hydroxyapatite (HA)-coated PLA microfibers compared to the pristine hydrogel construct. Furthermore, HA non-coated PLA microfibers were mixed with PRF and GelMA/alginate hydrogel to introduce a slow release of growth factors which can further enhance cell maturation and differentiation. These patient-specific bone grafts deliver cytokines and growth factors with distinct spatiotemporal release profiles to enhance tissue regeneration. The biocompatible and bio-responsive bone mimetic core-shell multi-material structures enhance osteogenesis and can be customized to have materials at a specific location, geometry, and material combination.

New dimensions of electrospun nanofiber material designs for biotechnological uses.

Electrospinning technology has garnered wide attention over the past few decades in various biomedical applications including drug delivery, cell therapy, and tissue engineering. This technology can create nanofibers with tunable fiber diameters and functionalities. However, the 2D membrane nature of the nanofibers, as well as the rigidity and low porosity of electrospun fibers, lower their efficacy in tissue repair and regeneration. Recently, new avenues have been explored to resolve the challenges associated with 2D electrospun nanofiber membranes. This review discusses recent trends in creating different electrospun nanofiber microstructures from 2D nanofiber membranes by using various post-processing methods, as well as their biotechnological applications.

Bioengineering strategies for 3D bioprinting of tubular construct using tissue-specific decellularized extracellular matrix.

The goal of the current study is to develop an extracellular matrix bioink that could mimic the biochemical components present in natural blood vessels. Here, we have used an innovative approach to recycle the discarded varicose vein for isolation of endothelial cells and decellularization of the same sample to formulate the decellularized extracellular matrix (dECM) bioink. The shift towards dECM bioink observed as varicose vein dECM provides the tissue-specific biochemical factors that will enhance the regeneration capability. Interestingly, the encapsulated umbilical cord mesenchymal stem cells expressed the markers of vascular smooth muscle cells because of the cues present in the vein dECM. Further, in vitro immunological investigation of dECM revealed a predominant M2 polarization which could further aid in tissue remodeling. A novel approach was used to fabricate vascular construct using 3D bioprinting without secondary support. The outcomes suggest that this could be a potential approach for patient- and tissue-specific blood vessel regeneration.

Modulation of 3D Printed Calcium-Deficient Apatite Constructs with Varying Mn Concentrations for Osteochondral Regeneration via Endochondral Differentiation.

Osteochondral regeneration remains a vital problem in clinical situations affecting both bone and cartilage tissues due to the low regeneration ability of cartilage tissue. Additionally, the simultaneous regeneration of bone and cartilage is difficult to attain due to their dissimilar nature. Thus, fabricating a single scaffold for both bone and cartilage regeneration remains challenging. Biomaterials are frequently employed to promote tissue restoration, but they still cannot replicate the structure of native tissue. This study aims to create a single biomaterial that could be used to regenerate both bone and cartilage. This study focuses on synthesizing calcium-deficient apatite (CDA) with the gradual addition of manganese. The phase stability and the effect of heat treatment on manganese-doped CDA were studied using X-ray diffraction (XRD) and Rietveld refinement. The obtained powders were tested for their 3-dimensional (3D) printing ability by fabricating cuboidal 3D structures. The 3D printed scaffolds were examined for external topography using field-emission scanning electron microscopy (FE-SEM) and were subjected to compression testing. In vitro biocompatibility and differentiation studies were performed to access their biocompatibility and differentiation capabilities. Reverse transcription-quantitative PCR (RT-qPCR) analysis was done to determine the gene expression of bone- and cartilage-specific markers. Mn helps in stabilizing the ß-TCP phase beyond its sintering temperature without being degraded to α-TCP. Mn addition in CDA improves the compressive strength of the fabricated scaffolds while keeping them biocompatible. The concentrations of Mn in the CDA ceramic were found to influence the differentiation behavior of MSCs in the fabricated scaffolds. Mn-doped CDA is a promising candidate to be used as a substitute material for bone, cartilage, and osteochondral defects to facilitate repair and regeneration via endochondral differentiation. 3D printing can assist in the fabrication of a multifunctional single-unit scaffold with varied Mn concentrations, which might be able to generate the two tissues in situ in an osteochondral defect.

Mechanically tunable photo-cross-linkable bioinks for osteogenic differentiation of MSCs in 3D bioprinted constructs.

3D bioprinting technique renders a plausible solution to tissue engineering applications, mainly bone tissue regeneration, which could provide the microenvironment with desired physical, chemical, and mechanical properties. However, the mechanical and structural stability of current natural polymers is a critical issue in the fabrication of bone tissue-engineered scaffolds. To overcome these issues, we have developed 3D bioprintable semi-synthetic polymers derived from natural (sodium alginate, A) and synthetic (polyethylene glycol, PEG) biopolymers. In order to enhance the cross-linking properties and biocompatibility, we have functionalized these polymers with acrylate and methacrylate chemical moieties. These selected combination of natural and synthetic polymers improved the mechanical strength due to the synergistic effect of covalent as well as ionic bond formation in the hydrogel system, which is evident from the tested tensile data. Further, the feasibility of 3D bioprinting of acrylate and methacrylate functionalized PEG and hydrogels have been tested for the biocompatibility of the fabricated structures with human umbilical cord mesenchymal stem cells (UMSCs). Further, these bioprinted scaffolds were investigated for osteogenic differentiation of UMSCs in two types of culture conditions: namely, i) with osteoinduction media (with OIM), ii) without osteoinduction media (w/o OIM). We have examined the osteoinductivity of scaffolds with the activity of alkaline phosphatase (ALP) content, and significant changes in the ALP activity was observed with the stiffness of developed materials. The extent osteogenic differentiation was observed by alizarin red staining and reverse transcription PCR analysis. Elevated levels of ALP, RUNX2 and COL1 gene expression has been observed in without OIM samples on week 1 and week 3. Further, our study showed that the synthesized alginate methacrylate (AMA) without osteoinduction supplement with young's modulus of 0.34 MPa has a significant difference in ALP quantity and gene expression over the other reported literature. Thus, this work plays a pivotal role in the development of 3D bioprintable and photo-cross-linkable hydrogels in osteogenic differentiation of mesenchymal stem cells.