Topographical regulation of stem cell differentiation by plant-derived micro/nanostructures

Electroactive Hydroxyapatite/Carbon Nanofiber Scaffolds for Osteogenic Differentiation of Human Adipose-Derived Stem Cells

Traditional bone defect treatments are limited by an insufficient supply of autologous bone, the immune rejection of allogeneic bone grafts, and high medical costs. To address this medical need, bone tissue engineering has emerged as a promising option. Among the existing tissue engineering materials, the use of electroactive scaffolds has become a common strategy in bone repair. However, single-function electroactive scaffolds are not sufficient for scientific research or clinical application. On the other hand, multifunctional electroactive scaffolds are often complicated and expensive to prepare. Therefore, we propose a new tissue engineering strategy that optimizes the electrical properties and biocompatibility of carbon-based materials. Here, a hydroxyapatite/carbon nanofiber (HAp/CNF) scaffold with optimal electrical activity was prepared by electrospinning HAp nanoparticle-incorporated polyvinylidene fluoride (PVDF) and then carbonizing the fibers. Biochemical assessments of the markers of osteogenesis in human adipose-derived stem cells (h-ADSCs) cultured on HAp/CNF scaffolds demonstrate that the material promoted the osteogenic differentiation of h-ADSCs in the absence of an osteogenic factor. The results of this study show that electroactive carbon materials with a fibrous structure can promote the osteogenic differentiation of h-ADSCs, providing a new strategy for the preparation and application of carbon-based materials in bone tissue engineering.

Hydrogel Nanosheets Confined 2D Rhombic Ice: A New Platform Enhancing Chondrogenesis

Nanoconfinement within flexible interfaces is a key step towards exploiting confinement effects in several biological and technological systems wherein flexible 2D materials are frequently utilized but are arduous to prepare. Hitherto unreported, the synthesis of 2D Hydrogel nanosheets (HNS) using a template- and catalyst-free process is developed representing a fertile ground for fundamental structure-property investigations. In due course of time, nucleating folds propagating along the edges trigger co-operative deformations of HNS generating regions of nanoconfinement within trapped water islands. These severely constricting surfaces force water molecules to pack within the nanoscale regime of HNS almost parallel to the surface bringing about phase transition into puckered rhombic ice with AA and AB Bernal stacking pattern, which was mostly restricted to Molecular dynamics (MD) studies so far. Interestingly, under high lateral pressure and spatial inhomogeneity within nanoscale confinement, bilayer rhombic ice structures were formed with an in-plane lattice spacing of 0.31 nm. In this work, a systematic exploration of rhombic ice formation within HNS has been delineated using High-resolution transmission electron microscopy (HRTEM), and its ultrathin morphology was examined using Atomic Force Microscopy (AFM). Scanning Electron Microscopy (SEM) images revealed high porosity while mechanical testing presented young's modulus of 155 kPa with ~84% deformation, whereas contact angle suggested high hydrophilicity. The combinations of nanosheets, porosity, nanoconfinement, hydrophilicity, and mechanical strength, motivated us to explore their application as a scaffold for cartilage regeneration, by inducing chondrogenesis of human Wharton Jelly derived mesenchymal stem cells (hWJ MSCs). HNS promoted the formation of cell aggregates giving higher number of spheroid formation and a marked expression of chondrogenic markers (ColI, ColII, ColX, ACAN and S-100), thereby providing some cues for guiding chondrogenic differentiation.

Stem Cell Membrane-Encapsulated Zeolitic Imidazolate Framework-8: A Targeted Nano-Platform for Osteogenic Differentiation

Mesenchymal stem cells (MSCs) have been recognized as one of the most promising pharmaceutical multipotent cells, and a key step for their wide application is to safely and efficiently regulate their activities. Various methods have been proposed to regulate the directional differentiation of MSCs during tissue regeneration, such as nanoparticles and metal ions. Herein, nanoscale zeolitic imidazolate framework-8 (ZIF-8), a Zn-based metal-organic framework, is modified to direct MSCs toward an osteoblast lineage. Specifically, ZIF-8 nanoparticles are encapsulated using stem cell membranes (SCMs) to mimic natural molecules and improve the biocompatibility and targeted ability toward MSCs. SCM/ZIF-8 nanoparticles adjust the sustained release of Zn²⁺ , and promote their specific internalization toward MSCs. The internalized SCM/ZIF-8 nanoparticles show excellent biocompatibility, and increase MSCs' osteogenic potentials. Moreover, RNA-sequencing results elucidate that the activated cyclic adenosine 3,5-monophosphate (cAMP)-PKA-CREB signaling pathway can be dominant in accelerating osteogenic differentiation. In vivo, SCM/ZIF-8 nanoparticles greatly promote the formation of new bone tissue in the femoral bone defect detected by 3D micro-CT, hematoxylin and eosin staining, and Masson staining after 4 weeks. Overall, the SCM-derived ZIF-8 nanostructures achieve the superior targeting ability, biocompatibility, and enhanced osteogenesis, providing a constructive design for tissue repair.