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

Pre-Clinical Assessment of Bupivacaine-Loaded Poly(ester urea) Thin Films for Controlled Drug Release and Effective Pain Management After Surgery

Safe, effective pain management remains one of the biggest challenges following surgical procedures. Despite widespread recognition of this problem and advances in the mechanistic understanding of pain signaling, post-surgical pain is often undermanaged, with opioid use remaining the clinical standard. As an alternative to current oral, systemic treatments, a degradable bupivacaine-loaded poly(ester urea) (PEU) thin film has been developed to deliver bupivacaine directly to the site of injury over an extended duration. The dose and duration of bupivacaine delivery is controlled using polymer composition and bupivacaine concentration. Systemic bupivacaine concentrations are more than an order of magnitude lower when delivered locally versus intravenous injection. Tissue analysis showed that the majority of bupivacaine is deposited into subcutaneous tissue directly surrounding the implant. Bupivacaine concentration in soft tissue around the implant are 30-fold higher than plasma values, indicating that release from PEU implants remains localized. Bupivacaine-loaded PEU films are assessed into two established mouse models for diabetic neuropathic pain and post-surgical incisional pain. In each model, bupivacaine eluting PEU films effectively block pain for 3-5 days before returning to baseline levels without loss of motor function and without signs of neurotoxicity.

Amino Acid-Based Poly(ester urea) Biodegradable Membrane for Guided Bone Regeneration

Barrier membranes (BM) for guided bone regeneration (GBR) aim to support the osteogenic healing process of a defined bony defect by excluding epithelial (gingival) ingrowth and enabling osteoprogenitor and stem cells to proliferate and differentiate into bone tissue. Currently, the most widely used membranes for these approaches are collagen-derived, and there is a discrepancy in defining the optimal collagen membrane in terms of biocompatibility, strength, and degradation rates. Motivated by these clinical observations, we designed a collagen-free membrane based on l-valine-co-l-phenylalanine-poly(ester urea) (PEU) copolymer via electrospinning. Degradation and mechanical properties of these membranes were performed on as-spun and water-aged samples. Alveolar-bone-derived stem cells (AvBMSCs) were seeded on the PEU BM to assess their cell compatibility and osteogenic characteristics, including cell viability, attachment/spreading, proliferation, and mineralized tissue-associated gene expression. In vivo, PEU BMs were subcutaneously implanted in rats to evaluate their potential to cause inflammatory responses and facilitate angiogenesis. Finally, critical-size calvarial defects and a periodontal model were used to assess the regenerative capacity of the electrospun PEU BM compared to clinically available Cytoflex synthetic membranes. PEU BM demonstrated equal biocompatibility to Cytoflex with superior mechanical performance in strength and elasticity. Additionally, after 14 days, PEU BM exhibited a higher expression of BGLAP/osteocalcin and superior in vivo performance-less inflammation and increased CD31 and VWF expression over time. When placed in critical-sized defects in the calvaria of rats, the PEU BM led to robust bone formation with high expression of osteogenesis and angiogenesis markers. Moreover, our membrane enhanced alveolar bone and cementum regeneration in an established periodontal model after 8 weeks. We demonstrate that the PEU BM exhibits favorable clinical properties, including mechanical stability, cytocompatibility, and facilitated bone formation in vitro and in vivo. This highlights its suitability for GBR in periodontal and craniofacial bone defects.

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.

Anti-adhesive bioresorbable elastomer-coated composite hernia mesh that reduce intraperitoneal adhesions

Intraperitoneal adhesions (IAs) are a major complication arising from abdominal repair surgeries, including hernia repair procedures. Herein, we fabricated a composite mesh device using a macroporous monofilament polypropylene mesh and a degradable elastomer coating designed to meet the requirements of this clinical application. The degradable elastomer was synthesized using an organo-base catalyzed thiol-yne addition polymerization that affords independent control of degradation rate and mechanical properties. The elastomeric coating was further enhanced by the covalent tethering of antifouling zwitterion molecules. Mechanical testing demonstrated the elastomer forms a robust coating on the polypropylene mesh does not exhibit micro-fractures, cracks or mechanical delamination under cyclic fatigue testing that exceeds peak abdominal loads (50 N/cm). Quartz crystal microbalance measurements showed the zwitterionic functionalized elastomer further reduced fibrinogen adsorption by 73% in vitro when compared to unfunctionalized elastomer controls. The elastomer exhibited degradation with limited tissue response in a 10-week murine subcutaneous implantation model. We also evaluated the composite mesh in an 84-day study in a rabbit cecal abrasion hernia adhesion model. The zwitterionic composite mesh significantly reduced the extent and tenacity of IAs by 94% and 90% respectively with respect to uncoated polypropylene mesh. The resulting composite mesh device is an excellent candidate to reduce complications related to abdominal repair through suppressed fouling and adhesion formation, reduced tissue inflammation, and appropriate degradation rate.

Pulmonary delivery nanomedicines towards circumventing physiological barriers: Strategies and characterization approaches

Pulmonary delivery of nanomedicines is very promising in lung local disease treatments whereas several physiological barriers limit its application via the interaction with inhaled nanomedicines, namely bio-nano interactions. These bio-nano interactions may affect the pulmonary fate of nanomedicines and impede the distribution of nanomedicines in its targeted region, and subsequently undermine the therapeutic efficacy. Pulmonary diseases are under worse scenarios as the altered physiological barriers generally induce stronger bio-nano interactions. To mitigate the bio-nano interactions and regulate the pulmonary fate of nanomedicines, a number of manipulating strategies were established based on size control, surface modification, charge tuning and co-delivery of mucolytic agents. Visualized and non-visualized characterizations can be employed to validate the robustness of the proposed strategies. This review provides a guiding overview of the physiological barriers affecting the in vivo fate of inhaled nanomedicines, the manipulating strategies, and the validation methods, which will assist with the rational design and application of pulmonary nanomedicine.

Natural polyphenol-based nanoengineering of collagen-constructed hemoperfusion adsorbent for the excretion of heavy metals

Designing a hemoperfusion adsorbent for the excretion therapy of toxic heavy metals still remains a great challenge due to the biosafety risks of non-biological materials and the desired highly efficient removal capacity. Herein, inspired from the homeostasis mechanism of plants, natural polyphenols are integrated with collagen matrix to construct a polyphenol-functionalized collagen-based artificial liver (PAL) for heavy metals excretion and free radicals scavenging therapy. PAL presents high adsorption capacities for Cu²⁺, Pb²⁺, and UO₂²⁺ ions, up to 76.98 μmol g^-1, 106.70 μmol g^-1, and 252.48 μmol g^-1, respectively. Remarkably, PAL possesses a high binding affinity for UO₂²⁺, Pb²⁺, and Cu²⁺ ions even in the complex serum environment with the presence of biologically-relevant ions (e.g., Mg²⁺, Ca²⁺ ions). Low hemolysis ratio (1.77%), high cell viability (> 85%), high plasma recalcification time (17.4 min), and low protein adsorption (1.02 μmol g^-1) indicate outstanding biocompatibility of this material. This natural polyphenol/collagen-based fully bio-derived hemoperfusion adsorbent provides a novel and potentially applicable strategy for constructing a hemoperfusion adsorbent for heavy metal ions excretion therapy with efficiency and biosafety.

Physically Cross-Linked Hyaluronan-Based Ultrasoft Cryogel Prepared by Freeze-Thaw Technique as a Barrier for Prevention of Postoperative Adhesions

Postsurgical peritoneal adhesions are a common and serious postoperative complication after various peritoneal surgeries, such as pelvic and abdominal surgery. Various studies have shown that peritoneal adhesions can be minimized or prevented by physical anti-adhesion barriers, including membranes, knits, and hydrogels. Hydrogels have attracted great attention in preventing peritoneal adhesions because the dimensional architecture of hydrogels is similar to that of the native extracellular matrix. However, chemical cross-linkers had to be used in the preparation of chemical hydrogels, which may have problems in cytotoxicity or unwanted side effects. This fact prompts us to create alternative cross-linking methods for the development of biocompatible hydrogels as physical barriers. Herein, we report a physically cross-linked flexible hyaluronan (HA) cryogel prepared via a freeze-thaw technique as a novel anti-adhesion biomaterial for completely preventing postsurgical peritoneal adhesions. In vitro studies demonstrated that this physically cross-linked HA cryogel exhibited excellent biocompatibility, the inherently desirable biocompatibility and functionality of HA being integrally retained as much as possible. Intriguingly, the rheological properties and appropriate biodegradability of the cryogels were readily tailored and tunable by way of the gelation process. In vivo assessments suggested that the cryogel, as a physical barrier, satisfactorily prevented fibroblast penetration and attachment between the injured tissues and nearby normal organs. Furthermore, the molecular mechanism studies revealed that the HA cryogel could prevent peritoneal adhesion by inhibiting inflammatory response and modulation of the fibrinolytic system. Our results show that HA ultrasoft cryogel is a promising clinical candidate for prolonged adhesion prevention.

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.