Electrospun electroconductive constructs of aligned fibers for cardiac tissue engineering.

Myocardial infarction remains the leading cause of death in the western world. Since the heart has limited regenerative capabilities, several cardiac tissue engineering (CTE) strategies have been proposed to repair the damaged myocardium. A novel electrospun construct with aligned and electroconductive fibers combining gelatin, poly(lactic-co-glycolic) acid and polypyrrole that may serve as a cardiac patch is presented. Constructs were characterized for fiber alignment, surface wettability, shrinkage and swelling behavior, porosity, degradation rate, mechanical properties, and electrical properties. Cell-biomaterial interactions were studied using three different types of cells, Neonatal Rat Ventricular Myocytes (NRVM), human lung fibroblasts (MRC-5) and induced pluripotent stem cells (iPSCs). All cell types showed good viability and unique organization on construct surfaces depending on their phenotype. Finally, we assessed the maturation status of NRVMs after 14 days by confocal images and qRT-PCR. Overall evidence supports a proof-of-concept that this novel biomaterial construct could be a good candidate patch for CTE applications.

Double Network Hydrogels that Mimic the Modulus, Strength, and Lubricity of Cartilage.

The development of a hydrogel-based synthetic cartilage has the potential to overcome many limitations of current chondral defect treatments. Many attempts have been made to replicate the unique characteristics of cartilage in hydrogels, but none have simultaneously achieved high modulus, strength, and toughness while maintaining the necessary hydration required for lubricity. Herein, double network (DN) hydrogels, composed of a poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) first network and a poly( N-isopropylacrylamide- co-acrylamide) [P(NIPAAm- co-AAm)] second network, are evaluated as a potential off-the-shelf material for cartilage replacement. While predominantly used for its thermosensitivity, PNIPAAm is employed to achieve superior mechanical properties with its thermal transition temperature tuned above the physiological range. These PNIPAAm-based DNs demonstrate a 50-fold increase in compressive strength (∼25 MPa, similar to cartilage) compared to traditional single network hydrogels while also achieving cartilage-like modulus (∼1 MPa) and hydration (∼80%). In direct comparison to healthy cartilage (porcine), these hydrogels were confirmed to not only parallel the strength, modulus, and hydration of native articular cartilage but also exhibit a 50% lower coefficient of friction (COF). The exceptional cartilage-like properties of the PAMPS/P(NIPAAm- co-AAm) DN hydrogels makes them candidates for synthetic cartilage grafts for chondral defect repair, even in load-bearing regions of the body.

Thermoresponsive Double Network Hydrogels with Exceptional Compressive Mechanical Properties.

The utility of thermoresponsive hydrogels, such as those based on poly(N-isopropylacrylamide) (PNIPAAm), is severely limited by their deficient mechanical properties. In particular, the simultaneous achievement of high strength and stiffness remains unreported. In this work, a thermoresponsive hydrogel is prepared having the unique combination of ultrahigh compressive strength (≈23 MPa) and excellent compressive modulus (≈1.5 MPa). This is accomplished by employing a double network (DN) design comprised of a tightly crosslinked, highly negatively charged 1st network based on poly(2-acrylamido-2-methylpropane sulfonic acid (PAMPS) and a loosely crosslinked, zwitterionic 2nd network based on a copolymer of thermoresponsive NIPAAm and zwitterionic 2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (MEDSAH). Comparison to other DN designs reveals that this PAMPS/P(NIPAAm-co-MEDSAH) DN hydrogel's remarkable properties stem from the intra- and internetwork ionic interactions of the two networks. Finally, this mechanically robust hydrogel retains the desirable thermosensitivity of PNIPAAm hydrogels, exhibiting a volume phase transition temperature of ≈35 °C.