Jiashing Yu

The use of human mesenchymal stem cells encapsulated in RGD modified alginate microspheres in the repair of myocardial infarction in the rat.

The combination of scaffold material and cell transplantation therapy has been extensively investigated in cardiac tissue engineering. However, many polymers are difficult to administer or lack the structural integrity to restore LV function. Additionally, polymers need to be biological friendly, favorably influence the microenvironment and increase stem cell retention and survival. This study determined whether human mesenchymal stem cells (hMSCs) encapsulated in RGD modified alginate microspheres are capable of facilitating myocardial repair. The in vitro study of hMSCs demonstrated that the RGD modified alginate can improve cell attachment, growth and increase angiogenic growth factor expression. Alginate microbeads and hMSCs encapsulated in microbeads successfully maintained LV shape and prevented negative LV remodeling after an MI. Cell survival was significantly increased in the encapsulated hMSC group compared with PBS control or cells alone. Microspheres, hMSCs, and hMSCs in microspheres groups reduced infarct area and enhanced arteriole formation. In summary, surface modification and microencapsulation techniques can be combined with cell transplantation leading to the maintenance of LV geometry, preservation of LV function, increase of angiogenesis and improvement of cell survival.

The effect of injected RGD modified alginate on angiogenesis and left ventricular function in a chronic rat infarct model.

Congestive heart failure (CHF) is a chronic disease with a high mortality rate. Managing CHF patients has been one of the most severe health care problems for years. Scaffold materials have been predominantly investigated in acute myocardial infarction (MI) studies and have shown promising improvement in LV function. In this study we examined whether surface modification of a biomaterial can influence the myocardial microenvironment and improve myocardial function in a rodent model of ischemic cardiomyopathy. In vitro cell culture and in vivo rat studies were performed. RGD peptides conjugated to alginate improved human umbilical vein endothelial cell (HUVEC) proliferation and adhesion when compared to a non-modified alginate group. Injection of the alginate hydrogel into the infarct area of rats 5 weeks post-MI demonstrated that both modified and non-modified alginate improve heart function, while LV function in the control group deteriorated. Both the RGD modified alginate and non-modified alginate increased the arteriole density compared to control, with the RGD modified alginate having the greatest angiogenic response. These results suggest that in situ use of modified polymers may influence the tissue microenvironment and serve as a potential therapeutic agent for patients with chronic heart failure.

Modulation of alignment, elongation and contraction of cardiomyocytes through a combination of nanotopography and rigidity of substrates

The topographic and mechanical characteristics of engineered tissue constructs, simulating native tissues, should benefit tissue engineering. Previous studies reported that surface topography and substrate rigidity provide biomechanical cues to modulate cellular responses such as alignment, migration and differentiation. To fully address this issue, the present study aimed to examine the influence of nanogrooved substrates with different stiffnesses on the responses of rat cardiomyocytes. Nanogrooved substrates (450nm in groove/ridge width; 100 or 350nm in depth) made of polystyrene and polyurethane were prepared by imprinting from polydimethylsiloxane molds. The morphology and orientation of cardiomyocytes attached to the substrates were found to be influenced mainly by the nanogrooved structures, while the contractile function of the cells was regulated by the coupled effect of surface topography and substrate stiffness. The distribution of intracellular structural proteins such as vinculin and F-actin showed that the surface topography and substrate stiffness regulated the organization of the actin cytoskeleton and focal adhesion complexes, and consequently the contractile behavior of the cardiomyocytes. The beating rates of the cultured cardiomyocytes were dependent on both the surface topography and the substrate stiffness. The study provides insights into the interaction between cardiomyocytes and biomaterials, and benefits cardiac tissue engineering.

Restoration of left ventricular geometry and improvement of left ventricular function in a rodent model of chronic ischemic cardiomyopathy

OBJECTIVES Various approaches to myocardial reconstruction have been developed for the treatment of congestive heart failure resulting from ischemic cardiomyopathy. METHODS In this study we determined whether in situ application of polymers could reshape left ventricular geometry in a chronic rodent model of ischemic cardiomyopathy. RESULTS We demonstrate that alginate and fibrin can augment left ventricular wall thickness, resulting in reconstruction of left ventricular geometry and improvement of cardiac function. Echocardiographic results at 5 weeks after injection of alginate demonstrated persistent improvement of left ventricular fractional shortening and prevention of a continued enlargement of left ventricular dimensions, whereas fibrin glue demonstrated no progression of left ventricular negative remodeling. There was increased arteriogenesis in both the alginate and fibrin glue groups compared with that seen in the phosphate-buffered saline control group. Infarct size was significantly reduced in the fibrin group (P < .05), and there was a trend toward a smaller myocardial infarction in the alginate group. CONCLUSION Intramyocardially injected polymers can be used to reshape the aneurysmal left ventricle and might therefore be an approach for myocardial reconstruction and a potential option in treating chronic heart failure in human subjects.

Reactive Polymer Coatings: A General Route to Thiol-ene and Thiol-yne Click Reactions

Reactive polymer coatings were synthesized via chemical vapor deposition (CVD) polymerization process. These coatings decouple surface design from bulk properties of underlying materials and provide a facile and general route to support thiol-ene and thiol-yne reactions on a variety of substrate materials. Through the reported technique, surface functions can be activated through a simple design of thiol-terminated molecules such as polyethylene glycols (PEGs) or peptides (GRGDYC), and the according biological functions were demonstrated in controlled and low-fouling protein adsorptions as well as accurately manipulated cell attachments.

Stemness and transdifferentiation of adipose-derived stem cells using L-ascorbic acid 2-phosphate-induced cell sheet formation.

Cell sheet technology has emerged as an important tissue engineering approach. Adipose-derived stem cells (ASCs) have valuable applications in regenerative medicine, but their stemness and differentiation capabilities in the cell sheet format have not been well investigated. In this study, we found that l-ascorbate 2-phosphate (A2-P), a stable form of ascorbic acid, significantly enhanced ASC proliferation and induced ASC sheet fabrication in 7 days with abundant extracellular matrix deposition. Importantly, A2-P treatment significantly enhanced expression of pluripotent markers Sox-2, Oct-4 and Nanog, but treating ASCs with antioxidants other than A2-P revealed no stemness enhancement. Moreover, ASC treatment with A2-P and a collagen synthesis inhibitor, L-2-azetidine carboxylic acid or cis-4-hydroxy-d-proline, significantly inhibited the A2-P-enhanced expression of stemness markers. These findings demonstrated that A2-P enhances stemness of ASCs through collagen synthesis and cell sheet formation. We also showed that A2-P-stimulated collagen synthesis in ASCs may be mediated through ERK1/2 pathway. By culturing the ASC sheets in proper induction media, ASC transdifferentiation capabilities into neuron and hepatocyte-like cells were significantly enhanced after cell sheet formation, while adipogenic and osteogenic differentiation capacities were still maintained. Using a murine model of healing-impaired cutaneous wound, faster wound healing was noted in the group that received ASC sheet treatment, and we observed significantly more engrafted ASCs with evidence of differentiation toward endothelial and epidermal lineages in the cutaneous wound tissue. Therefore, A2-P-mediated ASC sheet formation enhanced ASC stemness and transdifferentiation capabilities, thereby representing a promising approach for applications in regenerative medicine.

Liver cancer cells: Targeting and prolonged-release drug carriers consisting of mesoporous silica nanoparticles and alginate microspheres

A new microsphere consisting of inorganic mesoporous silica nanoparticles (MSNs) and organic alginate (denoted as MSN@Alg) was successfully synthesized by air-dynamic atomization and applied to the intracellular drug delivery systems (DDS) of liver cancer cells with sustained release and specific targeting properties. MSN@Alg microspheres have the advantages of MSN and alginate, where MSN provides a large surface area for high drug loading and alginate provides excellent biocompatibility and COOH functionality for specific targeting. Rhodamine 6G was used as a model drug, and the sustained release behavior of the rhodamine 6G-loaded MSN@Alg microspheres can be prolonged up to 20 days. For targeting therapy, the anticancer drug doxorubicin was loaded into MSN@Alg microspheres, and the (lysine)4-tyrosine-arginine-glycine-aspartic acid (K4YRGD) peptide was functionalized onto the surface of MSN@Alg for targeting liver cancer cells, hepatocellular carcinoma (HepG2). The results of the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay and confocal laser scanning microscopy indicate that the MSN@Alg microspheres were successfully uptaken by HepG2 without apparent cytotoxicity. In addition, the intracellular drug delivery efficiency was greatly enhanced (ie, 3.5-fold) for the arginine-glycine-aspartic acid (RGD)-labeled, doxorubicin-loaded MSN@Alg drug delivery system compared with the non-RGD case. The synthesized MSN@Alg microspheres show great potential as drug vehicles with high biocompatibility, sustained release, and targeting features for future intracellular DDS.

One-step shell polymerization of inorganic nanoparticles and their applications in SERS/nonlinear optical imaging, drug delivery, and catalysis

Surface functionalized nanoparticles have found their applications in several fields including biophotonics, nanobiomedicine, biosensing, drug delivery, and catalysis. Quite often, the nanoparticle surfaces must be post-coated with organic or inorganic layers during the synthesis before use. This work reports a generally one-pot synthesis method for the preparation of various inorganic-organic core-shell nanostructures (Au@polymer, Ag@polymer, Cu@polymer, Fe3O4@polymer, and TiO2@polymer), which led to new optical, magnetic, and catalytic applications. This green synthesis involved reacting inorganic precursors and poly(styrene-alt-maleic acid). The polystyrene blocks separated from the external aqueous environment acting as a hydrophobic depot for aromatic drugs and thus illustrated the integration of functional nanoobjects for drug delivery. Among these nanocomposites, the Au@polymer nanoparticles with good biocompatibility exhibited shell-dependent signal enhancement in the surface plasmon resonance shift, nonlinear fluorescence, and surface-enhanced Raman scattering properties. These unique optical properties were used for dual-modality imaging on the delivery of the aromatic photosensitizer for photodynamic therapy to HeLa cells.

Gelatin methacrylate/carboxybetaine methacrylate hydrogels with tunable crosslinking for controlled drug release

In this work, methacrylated gelatin (GelMA) based hydrogels were fabricated with carboxybetaine methacrylate (CBMA) to manipulate the properties of the gelatin-based hydrogels, since CBMA is a much smaller compound compared to gelatin. With the incorporation of CBMA, these hydrogels demonstrated better mechanical properties, a slower degradation rate, and a controlled drug release rate compared with the GelMA alone group. GelMA/CBMA hydrogels also showed good cell viability. As in the in vivo test, vascular endothelial growth factor (VEGF)-loaded GelMA/CBMA hydrogels displayed certain degrees of angiogenesis. These results indicate that GelMA/CBMA hydrogels are biocompatible, and the properties of GelMA/CBMA hydrogels can be easily tuned with the ratio of CBMA. These characteristics make the GelMA/CBMA hydrogel a promising material for drug delivery and tissue engineering.

Sustained immobilization of growth factor proteins based on functionalized parylenes.

Protein molecules immobilized on biomaterial surfaces are performed based on oriented conjugation or replaced mimicking peptides. The sustainable immobilization of growth factor proteins using functionalized parylene coatings is demonstrated in this study. Site-specific and nonspecific immobilization approaches are realized to conjugate bone morphogenetic protein (BMP-2). The binding affinities and conformational changes of BMP-2 are confirmed by QCM and SPR characterizations. Osteoinduction of stem cells is examined by ALP activity on the BMP-2 modified surfaces. Finally, immobilizations and equally sustained biological functions of vascular endothelial growth factor (VEGF) and a mimicking peptide of KLTWQELYQLKYKG (QK) are also examined and confirmed.