Preclinical in Vitro and in Vivo Assessment of Linear and Branched l-Valine-Based Poly(ester urea)s for Soft Tissue Applications

An antibacterial biologic patch based on bacterial cellulose for repair of infected hernias

Infection-associated complications and repair failures and antibiotic resistance have emerged as a formidable challenge in hernia repair surgery. Consequently, the development of antibiotic-free antibacterial patches for hernia repair has become an exigent clinical necessity. Herein, a GBC/Gel/LL37 biological patch (biopatch) with exceptional antibacterial properties is fabricated by grafting 2-Methacryloyloxyethyl trimethylammonium chloride (METAC), a unique quaternary ammonium salt with vinyl, onto bacterial cellulose (GBC), followed by compounding with gelatin (Gel) and LL37. The GBC/Gel/LL37 biopatch exhibits stable swelling capacity, remarkable mechanical properties, flexibility, and favorable biocompatibility. The synergistic effect of METAC and LL37 confers upon the GBC/Gel/LL37 biopatch excellent antibacterial efficacy against Staphylococcus aureus and Escherichia coli, effectively eliminating invading bacteria without the aid of exogenous antibiotics in vivo while significantly reducing local acute inflammation caused by infection. Furthermore, the practical efficacy of the GBC/Gel/LL37 biopatch is evaluated in an infected ventral hernia model, revealing that the GBC/Gel/LL37 biopatch can prevent the formation of visceral adhesions, facilitate the repair of infected ventral hernia, and effectively mitigate chronic inflammation. The prepared antibacterial GBC/Gel/LL37 biopatch is very effective in dealing with the risk of infection in hernia repair surgery and offers potential clinical opportunities for other soft injuries, exhibiting considerable clinical application prospects.

A Review of Advanced Abdominal Wall Hernia Patch Materials

Tension-free abdominal wall hernia patch materials (AWHPMs) play an important role in the repair of abdominal wall defects (AWDs), which have a recurrence rate of <1%. Nevertheless, there are still significant challenges in the development of tailored, biomimetic, and extracellular matrix (ECM)-like AWHPMs that satisfy the clinical demands of abdominal wall repair (AWR) while effectively handling post-operative complications associated with abdominal hernias, such as intra-abdominal visceral adhesion and abnormal healing. This extensive review presents a comprehensive guide to the high-end fabrication and the precise selection of these advanced AWHPMs. The review begins by briefly introducing the structures, sources, and properties of AWHPMs, and critically evaluates the advantages and disadvantages of different types of AWHPMs for AWR applications. The review subsequently summarizes and elaborates upon state-of-the-art AWHPM fabrication methods and their key characteristics (e.g., mechanical, physicochemical, and biological properties in vitro/vivo). This review uses compelling examples to demonstrate that advanced AWHPMs with multiple functionalities (e.g., anti-deformation, anti-inflammation, anti-adhesion, pro-healing properties, etc.) can meet the fundamental clinical demands required to successfully repair AWDs. In particular, there have been several developments in the enhancement of biomimetic AWHPMs with multiple properties, and additional breakthroughs are expected in the near future.

Long-term in vivo degradation and biocompatibility of degradable pHEMA hydrogels containing graphene oxide

Developing biocompatible, non-fouling and biodegradable hydrogels for blood-contacting devices remains a demanding challenge. Such materials should promote natural healing, prevent clotting, and undergo controlled degradation. This study evaluates the biocompatibility and biodegradation of degradable poly(2-hydroxyethyl methacrylate) (d-pHEMA) hydrogels with or without reinforcement with oxidized few-layer graphene (d-pHEMA/M5ox) in a long term implantation in rats, assessing non-desired side-effects (irritation, chronic toxicity, immune response). Subcutaneous implantation over 6 months revealed degradation of both hydrogels, despite slower for d-pHEMA/M5ox, with degradation products found in intracellular vesicles. No inflammation nor infection at implantation areas were observed, and no histopathological findings were detected in parenchymal organs. Immunohistochemistry confirmed d-pHEMA and d-pHEMA/M5ox highly anti-adhesiveness. Gene expression of macrophages markers revealed presence of both M1 and M2 macrophages at all timepoints. M1/M2 profile after 6 months reveals an anti-inflammatory environment, suggesting no chronic inflammation, as also demonstrated by cytokines (IL-α, TNF-α and IL-10) analysis. Overall, modification of pHEMA towards a degradable material was successfully achieved without evoking a loss of its inherent properties, specially its anti-adhesiveness and biocompatibility. Therefore, these hydrogels hold potential as blank-slate for further modifications that promote cellular adhesion/proliferation for tissue engineering applications, namely for designing blood contacting devices with different load bearing requirements. STATEMENT OF SIGNIFICANCE: Biocompatibility, tunable biodegradation kinetics, and suitable immune response with lack of chronic toxicity and irritation, are key features in degradable blood contact devices that demand long-term exposure. We herein evaluate the 6-month in vivo performance of a degradable and hemocompatible anti-adhesive hydrogel based in pHEMA, and its mechanically reinforced formulation with few-layer graphene oxide. This subcutaneous implantation in a rat model, shows gradual degradation with progressive changes in material morphology, and no evidence of local inflammation in surrounding tissue, neither signs of inflammation or adverse reactions in systemic organs, suggesting biocompatibility of degradation products. Such hydrogels exhibit great potential as a blank slate for tissue engineering applications, including for blood contact, where cues for specific cells can be incorporated.

Concomitant control of mechanical properties and degradation in resorbable elastomer-like materials using stereochemistry and stoichiometry for soft tissue engineering

Complex biological tissues are highly viscoelastic and dynamic. Efforts to repair or replace cartilage, tendon, muscle, and vasculature using materials that facilitate repair and regeneration have been ongoing for decades. However, materials that possess the mechanical, chemical, and resorption characteristics necessary to recapitulate these tissues have been difficult to mimic using synthetic resorbable biomaterials. Herein, we report a series of resorbable elastomer-like materials that are compositionally identical and possess varying ratios of cis:trans double bonds in the backbone. These features afford concomitant control over the mechanical and surface eroding degradation properties of these materials. We show the materials can be functionalized post-polymerization with bioactive species and enhance cell adhesion. Furthermore, an in vivo rat model demonstrates that degradation and resorption are dependent on succinate stoichiometry in the elastomers and the results show limited inflammation highlighting their potential for use in soft tissue regeneration and drug delivery.

Controlled release of etoricoxib from poly(ester urea) films for post-operative pain management

Medical prescriptions for the alleviation of post-surgical pain are the most abundant source of opioids in circulation. As a systemic drug delivery source, opioids leave patients at high risk for side effects after being dosed. Given the significant rate of unauthorized use, distribution, addiction, and opioid related deaths, an alternative method of post-surgical analgesia is needed. Herein, we report the use of bio-resorbable poly(ester urea) (PEU) films that controllably deliver a non-opioid COX-2 inhibitor, etoricoxib, in vivo and in vitro as a model system for post-surgical pain control. PEU composition, drug-load, and film thickness were varied to selectively control etoricoxib elution. Elution data were fit to a Higuchi model, and the diffusion constant of etoricoxib was calculated in each of the films. Pharmacokinetic (pK) data from an in vivo rat model showed the local tissue concentration of etoricoxib at the study endpoint to be up to 23-fold higher in tissue then plasma. In a well-established mouse model of diabetic neuropathic pain in vivo film implantation showed effective relief of pain for more than 4 days post-implantation and efficacious local etoricoxib delivery. Overall, implementation of local drug delivery systems such as this could reduce the need for opioid prescriptions associated with current pain management strategies.

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.

Zwitterionic amino acid-based Poly(ester urea)s suppress adhesion formation in a rat intra-abdominal cecal abrasion model

Hernia repair outcomes have improved with more robust material options for surgeons and optimized surgical techniques. However, ventral hernia repairs remain challenging with an inherent risk of post-surgical adhesions in the peritoneal space which can occur regardless of interventional material or its surgical placement. Herein, amino acid-based poly(ester urea)s (PEUs) with varied amount of an allyl ether side chains were modified post polymerization modification with the zwitterionic sulfnate group (3-((3-((3-mercaptopropanoyl)oxy)propyl) dimethylammonio)propane-1-sulfonate) to promote anti-adhesive properties. These alloc-PEUs were processed using roll-to-roll fabrication methods to afford films that were amenable to surface functionalization via a zwitterion-thiol. Functional group availability on the surface was confirmed via fluorescence microscopy, x-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance (QCM) measurements. Zwitterionic treated PEUs exhibited reduced fibrinogen adsorption in vitro when compared to unfunctionalized control polymer. A rat intrabdominal cecal abrasion adhesion model was used to assess the extent and tenacity of adhesion formation in the presence of the PEUs. The 10% alloc-PEU zwitterion functionalized material was found to reduce the extent and tenacity of adhesions when compared to adhesion controls and the unfunctionalized PEU controls.