•Surface chemistry of poly(ε-caprolactone) films actively modulates MSC behaviors.•Varying surface chemistry and pore size in combination is enabled in 3D scaffolds.•Surface chemistry and pore size potentially dictate MSC fates in synergy.Biomaterial properties play significant roles in controlling cellular behaviors. The objective of the present study was to investigate how pore size and surface chemistry of three-dimensional (3D) porous scaffolds regulate the fate of mesenchymal stem cells (MSCs) in vitro in combination. First, on poly(ε-caprolactone) (PCL) films, the hydrolytic treatment was found to stimulate the adhesion, spreading and proliferation of human MSCs (hMSCs) in comparison with pristine films, while the aminolysis showed mixed effects. Then, 3D porous PCL scaffolds with varying pore sizes (100–200 μm, 200–300 μm and 300–450 μm) were fabricated and subjected to either hydrolysis or aminolysis. It was found that a pore size of 200–300 μm with hydrolysis in 3D scaffolds was the most favorable condition for growth of hMSCs. Importantly, while a pore size of 200–300 μm with hydrolysis for 1 h supported the best osteogenic differentiation of hMSCs, the chondrogenic differentiation was greatest in scaffolds with a pore size of 300–450 μm and treated with aminolysis for 1 h. Taken together, these results suggest that surface chemistry and pore size of 3D porous scaffolds may potentially have a synergistic impact on the behaviors of MSCs.

•A series of poly(ϵ-caprolactone) polymers bearing pendant small groups was prepared.•Surface properties of this polymer series were characterized.•Biological behaviors of human MSCs were evaluated on this series of polymer films.•Roles of surface chemistry in modulating stem cell behaviors are highlighted.Probing stem cell–biomaterial interactions is of great significance in both gaining profound understanding of stem cell biology and advancing tissue regeneration. In the present work, we developed a series of poly(ϵ-caprolactone) (PCL) films bearing distinct pendant small functional groups to study the effects of biomaterial substrate chemistry on stem cell behaviors. PCL films, bearing hydroxyl (OH), methyl (CH3), carboxyl (COOH) and amino (NH2), demonstrated varied surface properties, such as wettability, serum protein adsorption and surface topographical feature. In comparison with pristine PCL film, the adhesion of hMSCs on PCL–COOH, PCL–OH and PCLCO films was significantly promoted and cells slightly outgrew on PCL–NH2 and PCL–COOH films. Most importantly, the tri-lineage differentiation of hMSCs varied on this series of PCL films, with the best osteogenesis achieved on PCL–NH2 film, PCL and PCL–CH3 films supporting the superior adipogenic differentiation and PCL–CH3 film being the most favorable one for chondrogenesis. This study highlights the critical roles of surface chemistry in modulating the fates of MSCs and potentially provides a practical guidance in developing instructive tissue engineering scaffolds.

In tissue engineering, incorporation of bone morphogenetic protein-2 (BMP-2) into biomaterial scaffolds is an attractive strategy to stimulate bone repair. However, suboptimal release of BMP-2 remains a great concern, which may cause unfavorable bone formation as well as severe inflammation. In this study, genipin-cross-linked gelatin entrapped with recombinant human BMP-2 (rhBMP-2) was exploited to decorate the interior surface of three-dimensional porous poly(ε-caprolactone) (PCL) scaffolds. With gelatin-coating, PCL scaffolds demonstrated enhanced water uptake and improved compressive moduli. Intriguingly, a unique release profile of rhBMP-2 composed of a transient burst release followed by a sustained release was achieved in coated scaffolds. These coated scaffolds well supported growth and osteogenesis of human mesenchymal stem cells (hMSCs) in vitro, indicating the retaining of rhBMP-2 bioactivity. When hMSCs-seeded scaffolds were implanted subcutaneously in nude mice for 4 weeks, better bone formation was observed in gelatin/rhBMP-2-coated scaffolds. Specifically, the spatial distribution of newly formed bone was more uniform in gelatin-coated scaffolds than in uncoated scaffolds, which displayed preferential bone formation at the periphery. These results collectively demonstrated that gelatin-coating of porous PCL scaffolds is a promising approach for delivering rhBMP-2 to stimulate improved bone regeneration.

The physical properties of tissue engineering scaffolds such as microstructures play important roles in controlling cellular behaviors and neotissue formation. Among them, the pore size stands out as a key determinant factor. In the present study, we aimed to fabricate porous scaffolds with pre-defined hierarchical pore sizes, followed by examining cell growth in these scaffolds. This hierarchical porous microstructure was implemented via integrating different pore-generating methodologies, including salt leaching and thermal induced phase separation (TIPS). Specifically, large (L, 200–300 μm), medium (M, 40–50 μm) and small (S, < 10 μm) pores were able to be generated. As such, three kinds of porous scaffolds with a similar porosity of ~ 90% creating pores of either two (LS or MS) or three (LMS) different sizes were successfully prepared. The number fractions of different pores in these scaffolds were determined to confirm the hierarchical organization of pores. It was found that the interconnectivity varied due to the different pore structures. Besides, these scaffolds demonstrated similar compressive moduli under dry and hydrated states. The adhesion, proliferation, and spatial distribution of human fibroblasts within the scaffolds during a 14-day culture were evaluated with MTT assay and fluorescence microscopy. While all three scaffolds well supported the cell attachment and proliferation, the best cell spatial distribution inside scaffolds was achieved with LMS, implicating that such a controlled hierarchical microstructure would be advantageous in tissue engineering applications.Highlights► The scaffolds with dual-pore and triple-pore structures were fabricated. ► Triple-pore structure had better interconnectivity than dual-pore structures. ► Better cell migration and distribution were found on the triple-pore structures. ► The medium pore size (45–50 μm) was appropriate for cell migration. ► Scaffolds with triple-pore structure should be advantageous in tissue engineering.

We report in this paper a facile way to prepare novel amine-functionalized monomethoxy-poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL) amphiphilic block copolymers, which are subsequently fluorescently labeled. In our synthetic route, monomethoxy-poly(ethylene glycol)-b-poly[ε-caprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] [mPEG-b-P(CL-co-CABCL)] copolymers were synthesized viaring-opening polymerization (ROP) of ε-caprolactone (CL) and a newly developed monomer, γ-(carbamic acid benzyl ester)-ε-caprolactone (CABCL) at varied ratios using mPEG as macroinitiator and Sn(Oct)2 as catalyst. Subsequent deprotection upon removal of carbobenzoxy (Cbz) group yielded monomethoxy-poly(ethylene glycol)-b-poly(ε-caprolactone-co-γ-amino-ε-caprolactone) [mPEG-b-P(CL-co-ACL)] copolymers bearing primary amine functional groups on the PCL block. The structures of polymers were characterized with NMR, FT-IR and GPC techniques. These amphiphilic block copolymers self-assembled into micelles in aqueous solution and the critical micelle concentration (CMC) was dependent on the compositions of the copolymers. In addition, the particle size and morphology of micelles were studied with DLS and TEM, respectively. In vitro study demonstrated that the micelles were nontoxic to human fibroblasts based on MTT and live/dead assays. Furthermore, a proof-of-concept usage of amino groups for bioconjugation was illustrated by tagging the copolymer with a fluorophore, fluorescein isothiocyanate (FITC). Internalization of FITC-labeled micelles by fibroblast cells was observed under fluorescence microscopy. Through facile conjugation of chemical moieties such as drugs, peptides, proteins or fluorophores, micelles prepared with these amine-functionalized mPEG-b-PCL copolymers hold great promise in biomedical applications.

This study aimed to optimize poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL)-based amphiphilic block copolymers for achieving a better micellar drug delivery system (DDS) with improved solubilization and delivery of doxorubicin (DOX). First, the Flory–Huggins interaction parameters between DOX and the core-forming segments [i.e., poly(ε-caprolactone) (PCL) and poly[(ε-caprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] (P(CL-co-CABCL))] was calculated to assess the drug–polymer compatibility. The results indicated a better compatibility between DOX and P(CL-co-CABCL) than that between DOX and PCL, motivating the synthesis of monomethoxy-poly(ethylene glycol)-b-poly[(ε-caprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] (mPEG-b-P(CL-co-CABCL)) block copolymer. Second, two novel block copolymers of mPEG-b-P(CL-co-CABCL) with different compositions were prepared via ring-opening polymerization of CL and CABCL using mPEG as a macroinitiator and characterized by 1H NMR, FT-IR, GPC, WAXD, and DSC techniques. It was found that the introduction of CABCL decreased the crystallinity of mPEG-b-PCL copolymer. Micellar formation of the copolymers in aqueous solution was investigated with fluorescence spectroscopy, DLS and TEM. mPEG-b-P(CL-co-CABCL) copolymers had a lower critical micelle concentration (CMC) than mPEG-b-PCL and subsequently led to an improved stability of prepared micelles. Furthermore, both higher loading capacity and slower in vitro release of DOX were observed for micelles of copolymers with increased content of CABCL, attributed to both improved drug–core compatibility and favorable amorphous core structure. Meanwhile, DOX-loaded micelles facilitated better uptake of DOX by HepG2 cells and were mainly retained in the cytosol, whereas free DOX accumulated more in the nuclei. However, possibly because of the slower intracellular release of DOX, DOX-loaded micelles were less potent in inhibiting cell proliferation than free DOX in vitro. Taken together, the introduction of CABCL in the core-forming block of mPEG-b-PCL resulted in micelles with superior properties, which hold great promise for drug delivery applications.

Heart failure remains the leading cause of morbidity and mortality. Recently, it was reported that the adult heart has intrinsic regenerative capabilities, prompting a great wave of research into applying cell-based therapies, especially with skeletal myoblasts and bone marrow-derived cells, to regenerate heart tissues. While the mechanism of action for the observed beneficial effects of bone marrow-derived cells remains unclear, new cell candidates are emerging, including embryonic stem (ES) and introduced pluripotent stem (iPS) cells, as well as cardiac stem cells (CSCs) from adult hearts. However, the very low engraftment efficiency and survival of implanted cells prevent cell therapy from turning into a clinical reality. Injectable hydrogel biomaterials based on hydrophilic, biocompatible polymers and peptides have great potential for addressing many of these issues by serving as cell/drug delivery vehicles and as a platform for cardiac tissue engineering. In this review, we will discuss the application of stem cells and hydrogels in myocardial regeneration.Download high-res image (474KB)Download full-size image

•A dynamic coculture in spinner flasks for chondrogenesis was established.•Chondrocytes and mesenchymal stem cells were encapsulated in alginate beads.•Separation between cocultured mesenchymal stem cells and chondrocytes was enabled.•Coculture with chondrocytes could improve chondrogenesis of mesenchymal stem cells.Coculture has emerged as a strategy to improve chondrogenesisof mesenchymal stem cells (MSCs) for cartilage regeneration. In the present study, a new system integrating cell encapsulation, dynamic stimulation and coculture with articular chondrocytes (ACs), termed as three-dimensional (3D) dynamic coculture, was developed for chondrogenic differentiation of MSCs. In addition, a novel mechanism was exploited to enable facile separation of cocultured cells. Rabbit bone-marrow derived MSCs (rMSCs) and rabbit ACs (rACs) were encapsualted in alginate gel beads, respectively. In rACs-laden beads, magnetic Fe3O4 nanoparticles were incorporated. Dynamic coculture was performed in a spinner flask. Fe3O4 nanoparticles had no negative effects on growth of rACs, although a slight inhibition on production of glycosaminoglycans (GAG) by rACs was noticed. An alginate concentration of above 1.8 w/v% was favorable for dynamic culture of rMSCs and rACs. Coculturing rMSCs with rACs in chondrogenic medium in this system demonstrated an improved chondrogenesis than monocultured rMSCs according to GAG quantification, histological staining, and gene expression analysis of collagen I, II and X. However, supplementation of 2% FBS did not show posive effects on chondrogenesis of cocultured rMSCs. This proof-of-concept study demonstrates that such a separable 3D dynamic coculture system holds great potential in cartilage tissue regeneration.