Calcium Trimetaphosphate-Loaded Electrospun Poly(Ester Urea) Nanofibers for Periodontal Tissue Engineering

The objective of this research was to create and appraise biodegradable polymer-based nanofibers containing distinct concentrations of calcium trimetaphosphate (Ca-TMP) for periodontal tissue engineering. Poly(ester urea) (PEU) (5% w/v) solutions containing Ca-TMP (15%, 30%, 45% w/w) were electrospun into fibrous scaffolds. The fibers were evaluated using SEM, EDS, TGA, FTIR, XRD, and mechanical tests. Degradation rate, swelling ratio, and calcium release were also evaluated. Cell/Ca-TMP and cell/scaffold interaction were assessed using stem cells from human exfoliated deciduous teeth (SHEDs) for cell viability, adhesion, and alkaline phosphatase (ALP) activity. Analysis of variance (ANOVA) and post-hoc tests were used (α = 0.05). The PEU and PEU/Ca-TMP-based membranes presented fiber diameters at 469 nm and 414-672 nm, respectively. Chemical characterization attested to the Ca-TMP incorporation into the fibers. Adding Ca-TMP led to higher degradation stability and lower dimensional variation than the pure PEU fibers; however, similar mechanical characteristics were observed. Minimal calcium was released after 21 days of incubation in a lipase-enriched solution. Ca-TMP extracts enhanced cell viability and ALP activity, although no differences were found between the scaffold groups. Overall, Ca-TMP was effectively incorporated into the PEU fibers without compromising the morphological properties but did not promote significant cell function.

Antibiotic eluting poly(ester urea) films for control of a model cardiac implantable electronic device infection

Cardiac implantable electronic device (CIED) infections acquired during or after surgical procedures are a major complication that are challenging to treat therapeutically, resulting in chronic and sometimes fatal infections. Localized delivery of antibiotics at the surgical site could be used to supplement traditional systemic administration as a preventative measure. Herein, we investigate a cefazolin-eluting l-valine poly(ester urea) (PEU) films as a model system for localized antibiotic delivery for CIEDs. Poly(1-VAL-8) PEU was used to fabricate a series of antibiotic-loaded films with varied loading concentrations (2%, 5%, 10% wt/wt) and thicknesses (40 µm, 80 µm, 140 µm). In vitro release measurements show thickness and loading concentration influence the amount and rate of cefazolin release. Group 10%-140 µm (load-thickness) showed 22.5% release of active pharmaceutical ingredient (API) in the first 24 h and 81.2% of cumulative percent release through day 14 and was found most effective in bacterial clearance in vitro. This group was also effective in clearing a bacterial infection in a model in vivo rat study while eliciting a limited inflammatory response. Our results suggest the feasibility of cefazolin-loaded PEU films as an effective sustained release matrix for localized delivery of antibiotics. SIGNIFICANCE STATEMENT: Implant-associated infections acquired during surgical procedures are a major complication that have proven a challenge to treat clinically, resulting in chronic and sometimes fatal infections. In this manuscript, we investigate an antibiotic-eluting L-valine poly(ester urea) (PEU) films as a model system for localized delivery of cefazolin. Significantly, we demonstrate a wide variation in temporal delivery and dosing within this family of PEUs and show that the delivery can be extended by varying the film thickness. The in vivo results show efficacy in an infected wound model and suggest antibiotic loaded PEU films function as an effective sustained release matrix for localized delivery of antibiotics across a number of clinical indications.

A Preliminary Evaluation of the Pro-Chondrogenic Potential of 3D-Bioprinted Poly(ester Urea) Scaffolds

Degeneration of articular cartilage (AC) is a common healthcare issue that can result in significantly impaired function and mobility for affected patients. The avascular nature of the tissue strongly burdens its regenerative capacity contributing to the development of more serious conditions such as osteoarthritis. Recent advances in bioprinting have prompted the development of alternative tissue engineering therapies for the generation of AC. Particular interest has been dedicated to scaffold-based strategies where 3D substrates are used to guide cellular function and tissue ingrowth. Despite its extensive use in bioprinting, the application of polycaprolactone (PCL) in AC is, however, restricted by properties that inhibit pro-chondrogenic cell phenotypes. This study proposes the use of a new bioprintable poly(ester urea) (PEU) material as an alternative to PCL for the generation of an in vitro model of early chondrogenesis. The polymer was successfully printed into 3D constructs displaying adequate substrate stiffness and increased hydrophilicity compared to PCL. Human chondrocytes cultured on the scaffolds exhibited higher cell viability and improved chondrogenic phenotype with upregulation of genes associated with type II collagen and aggrecan synthesis. Bioprinted PEU scaffolds could, therefore, provide a potential platform for the fabrication of bespoke, pro-chondrogenic tissue engineering constructs.

Poly(ester urea)-Based Adhesives: Improved Deployment and Adhesion by Incorporation of Poly(propylene glycol) Segments

The adhesive nature of mussels arises from the catechol moiety in the 3,4-dihydroxyphenylalanine (DOPA) amino acid, one of the many proteins that contribute to the unique adhesion properties of mussels. Inspired by these properties, many biomimetic adhesives have been developed over the past few years in an attempt to replace adhesives such as fibrin, cyanoacrylate, and epoxy glues. In the present work, we synthesized ethanol soluble but water insoluble catechol functionalized poly(ester urea) random copolymers that help facilitate delivery and adhesion in wet environments. Poly(propylene glycol) units incorporated into the polymer backbone impart ethanol solubility to these polymers, making them clinically relevant. A catechol to cross-linker ratio of 10:1 with a curing time of 4 h exceeded the performance of commercial fibrin glue (4.8 ± 1.4 kPa) with adhesion strength of 10.6 ± 2.1 kPa. These adhesion strengths are significant with the consideration that the adhesion studies were performed under wet conditions.

Pilot Mouse Study of 1 mm Inner Diameter (ID) Vascular Graft Using Electrospun Poly(ester urea) Nanofibers

An off-the-shelf, small diameter tissue engineered vascular graft (TEVG) would be transformative to surgeons in multiple subspecialties. Herein, the results of a small diameter (ID ≈ 1 mm) vascular graft constructed from resorbable, amino acid-based poly(ester urea) (PEU) are reported. Electrospun PEU grafts of two different wall thicknesses (type A: 250 μm; type B: 350 μm) are implanted as abdominal infra-renal aortic grafts in a severe combined immune deficient/beige mouse model and evaluated for vessel remodeling over one year. Significantly, the small diameter TEVG does not rupture or lead to acute thrombogenic events during the intervals tested. The pilot TEVG in vivo shows long-term patency and extensive tissue remodeling with type A grafts. Extensive tissue remodeling in type A grafts leads to the development of well-circumscribed neovessels with an endothelial inner lining, a neointima containing smooth muscle cells. However, due to slow degradation of the PEU scaffold materials in vivo, the grafts remain after one year. The type B grafts, which have 350 μm thick walls, experience occlusion over the one year interval due to intimal hyperplasia. This study affords significant findings that will guide the design of future generations of small diameter vascular grafts.