Search

Synthetic peptide conjugates that can molecularly target and activate blood platelets are designed for hemostasis applications. An engineered thrombin receptor-activating peptide (TRAP-Cys, SFLLRNPNC) is covalently attached to cell-compatible 8-arm poly (ethylene glycol) maleimides via Michael addition. It is proved that the ability of TRAP to activate platelets is retained in the conjugated form by means of thromboelastometry, platelet aggregation assay and flow cytometry. A 0.5 % PEG-TRAP solution can efficiently activate platelets and shorten the clotting time to ~45 %.

Template-mediated self-assembly synthesis has produced a diverse range of biomimetic materials with unique physicochemical properties. Here, we fabricated novel fluorescent three-dimensional (3-D) hydroxyapatite (HAP) nanorod-assembled microspheres using iron quantum cluster (FeQC) as a hybrid template, containing three organic components: hemoglobin chains, piperidine, and iron clusters. The material characterization indicated that the synthesized HAP possessed a uniform rod-like morphology, ordered 3-D architecture, high crystallinity, self-activated fluorescence, and remarkable photostability. Our study proposed that this FeQC template is a promising regulating agent to fabricate fluorescent self-assembled HAP microspheres with a controlled morphology. The effect of HAP on stem cell fate and their osteogenic differentiation was investigated by culturing human bone marrow-derived mesenchymal stromal/stem cells (BMSCs) with HAP microspheres. Significant increases in collagen matrix production and gene expression of osteogenic markers, including osteocalcin (OCN), Runt-related transcription factor 2 (Runx2), bone sialoprotein (BSP) and alkaline phosphatase (ALP), were observed compared to the controls after 21 days of culture. Taken together, our data suggest that synthetic HAP nanorod-assembled microspheres represent a promising new biomaterial which exhibits enhanced fluorescent properties and osteoinductive effects on human BMSCs.

Several hemostatic strategies rely on the use of blood components such as fibrinogen and thrombin, which suffer from high cost and short shelf-life. Here, a cost-effective synthetic biomaterial is developed for rapid local hemostasis. Instead of using thrombin, thrombin-receptor-agonist-peptide-6 (TRAP6) is covalently engineered in polyvinyl alcohol (PVA) hydrogels. Soluble PVA-TRAP6 is first prepared by covalent attachment of cysteine-containing TRAP6 onto the backbone of PVA-norbornenes (PVA-NB) through photoconjugation. Cytotoxicity studies using C2C12 myoblasts indicate that PVA-NB and PVA-TRAP6 are nontoxic. Thromboelastography reveals that hemostatic activity of TRAP6 is retained in conjugated form, which is comparable to free TRAP6 solutions with equal concentrations. A 0.1% PVA-TRAP6 solution can shorten the clotting time (CT) to ca. 45% of the physiological CT. High platelet-activating efficiency is further confirmed by platelet aggregation assay and flow cytometry (FACS). For potential clinical applications, TRAP6-presenting hydrogel particulates (PVA-TRAP6-P) are developed for local platelet activation and hemostasis. PVA-TRAP6-P is prepared by biofunctionalization of photopolymerized PVA-NB hydrogel particulates (PVA-NB-P) with TRAP6. It is demonstrated that PVA-TRAP6-P can effectively shorten the CT to ca. 50%. FACS shows that PVA-TRAP6-P can activate platelets to a comparable extent as soluble TRAP6 control. Altogether, PVA-TRAP6-P represents a promising class of biomaterials for safe hemostasis and wound healing.

Nanocrystalline hydroxyapatite (HA) has good biocompatibility and the potential to support bone formation. It represents a promising alternative to autologous bone grafting, which is considered the current gold standard for the treatment of low weight bearing bone defects. The purpose of this study was to compare three bone substitute pastes of different HA content and particle size with autologous bone and empty defects, at two time points (6 and 12 months) in an ovine scapula drillhole model using micro-CT, histology and histomorphometry evaluation. The nHA-LC (38% HA content) paste supported bone formation with a high defect bridging-rate. Compared to nHA-LC, Ostim® (35% HA content) showed less and smaller particle agglomerates but also a reduced defect bridging-rate due to its fast degradation The highly concentrated nHA-HC paste (48% HA content) formed oversized particle agglomerates which supported the defect bridging but left little space for bone formation in the defect site. Interestingly, the gold standard treatment of the defect site with autologous bone tissue did not improve bone formation or defect bridging compared to the empty control. We concluded that the material resorption and bone formation was highly impacted by the particle-specific agglomeration behaviour in this study.

A dual thermoresponsive and magnetic colloidal gel matrix is described for enhanced stem-cell culture. The combined properties of the material allow enzyme-free passaging and expansion of mesenchymal stem cells, as well as isolation of cells postculture by the simple process of lowering the temperature and applying an external magnetic field. The colloidal gel can be reconfigured with thermal and magnetic stimuli to allow patterning of cells in discrete zones and to control movement of cells within the porous matrix during culture.

Thermoreversible hydrogels for tissue engineering (TE) purposes have gained increased attention in recent years as they can be combined with cells and drugs and directly injected into the body. Following the fate of transplanted cells in situ is essential in characterizing their distribution and survival, as well as the expression of specific markers or cell-matrix interactions. Existing histological embedding methods, such as paraffin wax embedding, can mechanically damage some biomaterials during processing. In this study, we describe a broadly applicable preparation protocol that allows the handling of delicate, thermoreversible scaffolds for histological sectioning. The gelatin solution permits the embedding of samples at 37 °C, which suits the solid phase of most TE scaffolds. A thermoreversible scaffold of polycaprolactone microparticles, combined with poly(polyethylene glycol methacrylate ethyl ether) and containing human adipose-derived stem cells, was prepared for histology by an initial gelatin embedding step in addition to the standard cryosectioning and paraffin processing protocols. Sections were evaluated by hematoxylin eosin staining and immunostaining for human vimentin. The gelatin embedding retained the scaffold particles and permitted the complete transfer of the construct. After rapid cooling, the solid gelatin blocks could be cryosectioned and paraffin infiltrated. In contrast to direct cryosectioning or paraffin infiltration, the extended protocol preserved the scaffold structure as well as the relevant cell epitopes, which subsequently allowed for immunostaining of human cells within the material. The gelatin embedding method proposed is a generalizable alternative to standard preparations for histological examination of a variety of delicate samples.