Photoswitchable particles for on-demand degradation and triggered release.

On-demand degradable polymer particles are fabricated via electrospraying of a solution of acetal-protected dextran that further includes 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine as a photoacid generator. The illumination of UV light gives rise to photoacid and activates the catalytic deprotection of hydroxyl groups of dextran, leading to controlled dissolution of the microparticles in water.

Bacterial biosensors for evaluating potential impacts of estrogenic endocrine disrupting compounds in multiple species.

To study the effects and possible mechanisms of suspected endocrine disrupting compounds (EDCs), a wide variety of assays have been developed. In this work, we generated engineered Escherichia coli biosensor strains that incorporate the ligand-binding domains (LBDs) of the ß-subtype estrogen receptors (ERß) from Solea solea (sole), and Sus scrofa (pig). These strains indicate the presence of ligands for these receptors by changes in growth phenotype, and can differentiate agonist from antagonist and give a rough indication of binding affinity via dose-response curves. The resulting strains were compared with our previously reported Homo sapiens ERß biosensor strain. In initial tests, all three of the strains correctly identified estrogenic test compounds with a high degree of certainly (Z' typically greater than 0.5), including the weakly binding test compound bisphenol A (BPA) (Z' ≈ 0.1-0.3). The modular design of the sensing element in this strain allows quick development of new species-based biosensors by simple LBD swapping, suggesting its use in initial comparative analysis of EDC impacts across multiple species. Interestingly, the growth phenotypes of the biosensor strains indicate similar binding for highly estrogenic control compounds, but suggest differences in ligand binding for more weakly binding EDCs.

Bio-orthogonal polymer coatings for co-presentation of biomolecules.

Controlled presentation of biomolecules on synthetic substrates is an important aspect for biomaterials development. If the immobilization of multiple biomolecules is required, highly efficient orthogonal surface chemistries are needed to ensure the precision of the immobilization. In this communication, chemical vapor deposition (CVD) copolymerization is used to fabricate polymer coatings with controlled ratio of alkyne and pentafluorophenyl ester (Pfp-ester) groups. Cyclic argine-glycine-aspartic acid (cRGD) adhesion peptide and epidermal growth factor (EGF) are immobilized through alkyne-azide cycloaddtion ("click" chemistry) and active ester-amine reaction, respectively. Cell studies with human umbilical vein endothelial cells (HUVEC) and A431 cell lines demonstrate the biological activity of the coimmobilized biomolecules.

Simvastatin and nanofibrous poly(l-lactic acid) scaffolds to promote the odontogenic potential of dental pulp cells in an inflammatory environment.

In this study, we investigated the anti-inflammatory, odontogenic and pro-angiogenic effects of integrating simvastatin and nanofibrous poly(l-lactic acid) (NF-PLLA) scaffolds on dental pulp cells (DPCs). Highly porous NF-PLLA scaffolds that mimic the nanofibrous architecture of extracellular matrix were first fabricated, then seeded with human DPCs and cultured with 0.1 µM simvastatin and/or 10 µg/mL pro-inflammatory stimulator lipopolysaccharide (LPS). The gene expression of pro-inflammatory mediators (TNF-α, IL-1ß and MMP-9 mRNA) and odontoblastic markers (ALP activity, calcium content, DSPP, DMP-1 and BMP-2 mRNA) were quantified after long-term culture in vitro. In addition, we evaluated the scaffold's pro-angiogenic potential after 24 h of in vitro co-culture with endothelial cells. Finally, we assessed the combined effects of simvastatin and NF-PLLA scaffolds in vivo using a subcutaneous implantation mouse model. The in vitro studies demonstrated that, compared with the DPC/NF-PLLA scaffold constructs cultured only with pro-inflammatory stimulator LPS, adding simvastatin significantly repress the expression of pro-inflammatory mediators. Treating LPS+ DPC/NF-PLLA constructs with simvastatin also reverted the negative effects of LPS on expression of odontoblastic markers in vitro and in vivo. Western blot analysis demonstrated that these effects were related to a reduction in NFkBp65 phosphorylation and up-regulation of PPARγ expression, as well as to increased phosphorylation of pERK1/2 and pSmad1, mediated by simvastatin on LPS-stimulated DPCs. The DPC/NF-PLLA constructs treated with LPS/simvastatin also led to an increase in vessel-like structures, correlated with increased VEGF expression in both DPSCs and endothelial cells. Therefore, the combination of low dosage simvastatin and NF-PLLA scaffolds appears to be a promising strategy for dentin regeneration with inflamed dental pulp tissue, by minimizing the inflammatory reaction and increasing the regenerative potential of resident stem cells. STATEMENT OF SIGNIFICANCE: The regeneration potential of stem cells is dependent on their microenvironment. In this study, we investigated the effect of the microenvironment of dental pulp stem cells (DPSCs), including 3D structure of a macroporous and nanofibrous scaffold, the inflammatory stimulus lipopolysaccharide (LPS) and a biological molecule simvastatin, on their regenerative potential of mineralized dentin tissue. The results demonstrated that LPS upregulated inflammatory mediators and suppressed the odontogenic potential of DPSCs. Known as a lipid-lowing agent, simvastatin was excitingly found to repress the expression of pro-inflammatory mediators, up-regulate odontoblastic markers, and exert a pro-angiogenic effect on endothelial cells, resulting in enhanced vascularization and mineralized dentin tissue regeneration in a biomimetic 3D tissue engineering scaffold. This novel finding is significant for the fields of stem cells, inflammation and dental tissue regeneration.

3D Jet Writing: Functional Microtissues Based on Tessellated Scaffold Architectures.

The advent of adaptive manufacturing techniques supports the vision of cell-instructive materials that mimic biological tissues. 3D jet writing, a modified electrospinning process reported herein, yields 3D structures with unprecedented precision and resolution offering customizable pore geometries and scalability to over tens of centimeters. These scaffolds support the 3D expansion and differentiation of human mesenchymal stem cells in vitro. Implantation of these constructs leads to the healing of critical bone defects in vivo without exogenous growth factors. When applied as a metastatic target site in mice, circulating cancer cells home in to the osteogenic environment simulated on 3D jet writing scaffolds, despite implantation in an anatomically abnormal site. Through 3D jet writing, the formation of tessellated microtissues is demonstrated, which serve as a versatile 3D cell culture platform in a range of biomedical applications including regenerative medicine, cancer biology, and stem cell biotechnology.

Nanostructured injectable cell microcarriers for tissue regeneration.

Biodegradable polymer microspheres have emerged as cell carriers for the regeneration and repair of irregularly shaped tissue defects due to their injectability, controllable biodegradability and capacity for drug incorporation and release. Notably, recent advances in nanotechnology allowed the manipulation of the physical and chemical properties of the microspheres at the nanoscale, creating nanostructured microspheres mimicking the composition and/or structure of natural extracellular matrix. These nanostructured microspheres, including nanocomposite microspheres and nanofibrous microspheres, have been employed as cell carriers for tissue regeneration. They enhance cell attachment and proliferation, promote positive cell-carrier interactions and facilitate stem cell differentiation for target tissue regeneration. This review highlights the recent advances in nanostructured microspheres that are employed as injectable, biomimetic and cell-instructive cell carriers.

Dentin regeneration by stem cells of apical papilla on injectable nanofibrous microspheres and stimulated by controlled BMP-2 release.

UNLABELLED: The aim of this study was to investigate the effects of PLLA nanofibrous microspheres (NF-MS) as a cell delivery carrier in combination with controlled release of BMP-2 from PLGA microspheres on the induction of odontogenic differentiation of human stem cells of apical papilla (SCAP). Injectable NF-MS, which mimic the physical architecture of collagen fibers on the nano scale, were fabricated by combining thermally-induced phase separation techniques with an emulsification process. SCAP cultured in a monolayer or cultured on NF-MS in spinner flasks were treated with 100ng/ml BMP-2 in vitro. Odontogenic differentiation was characterized by measuring alkaline phosphatase activity, odontogenic gene expression levels, calcium content, and dentin sialophosphoprotein accumulation. The results demonstrated that BMP-2 enhanced human SCAP odontogenic differentiation both in monolayer culture and on 3D NF-MS in spinner flask culture in vitro. We also developed and tested a system combining NF-MS with controlled BMP-2 release for dentin regeneration in vivo. The results indicate that controlled release of BMP-2 promoted more mineralization and osteodentin formation compared to a BSA-releasing control in a dose-dependent and time-dependent manner. In summary, the NF-MS combined with controlled release of BMP-2 provides an excellent microenvironment for SCAP to regenerate dentin tissue. STATEMENT OF SIGNIFICANCE: Tooth lesion and loss affect masticatory efficiency, speaking function, facial aesthetics and even psychological health. Current treatments depend on "inert" restorative materials, which do not have the healing capacity and may lead to the failure of the restorations over a long term. The aim of this study was to develop an injectable biomaterial and desired growth factor delivery system to support stem cells for mineralized dental tissue regeneration. The study showed that novel injectable and biodegradable nanofibrous microspheres and controlled release of BMP-2 synergistically induce the odontogenic differentiation of human stem cells from the apical papilla and mineralized tissue regeneration, demonstrating the potential of living dental tissue repair.

Super stretchable electroactive elastomer formation driven by aniline trimer self-assembly.

Biomedical electroactive elastomers with a modulus similar to that of soft tissues are highly desirable for muscle, nerve, and other soft tissue replacement or regeneration, but have rarely been reported. In this work, superiorly stretchable electroactive polyurethane-urea elastomers were designed based on poly(lactide), poly(ethylene glycol), and aniline trimer (AT). A strain at break higher than 1600% and a modulus close to soft tissues was achieved from these copolymers. The mechanisms of super stretchability of the copolymer were systematically investigated. Crystallinity, chemical cross-linking, ionic cross-linking and hard domain formation were examined using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), nuclear magnetic resonance (NMR) measurements and transmission electron microscopy (TEM). The sphere-like hard domains self-assembled from AT segments were found to provide the crucial physical interactions needed for the novel super elastic material formation. These super stretchable copolymers were blended with conductive fillers such as polyaniline nanofibers and nanosized carbon black to achieve a high electric conductivity of 0.1 S/cm while maintaining an excellent stretchability and a modulus similar to that of soft tissues (lower than 10 MPa).