Emerging materials and technologies for advancing bioresorbable surgical meshes

Surgical meshes play a significant role in the treatment of various medical conditions, such as hernias, pelvic floor issues, guided bone regeneration, and wound healing. To date, commercial surgical meshes are typically made of non-absorbable synthetic polymers, notably polypropylene and polytetrafluoroethylene, which are associated with postoperative complications, such as infections. Biological meshes, based on native tissues, have been employed to overcome such complications, though mechanical strength has been a main disadvantage. The right balance in mechanical and biological performances has been achieved by the advent of bioresorbable meshes. Despite improvements, recurrence of clinical complications associated with surgical meshes raises significant concerns regarding the technical adequacy of current materials and designs, pointing to a crucial need for further development. To this end, current research focuses on the design of meshes capable of biomimicking native tissue and facilitating the healing process without post-operative complications. Researchers are actively investigating advanced bioresorbable materials, both synthetic polymers and natural biopolymers, while also exploring the performance of therapeutic agents, surface modification methods and advanced manufacturing technologies such as 4D printing. This review seeks to evaluate emerging biomaterials and technologies for enhancing the performance and clinical applicability of the next-generation surgical meshes. STATEMENT OF SIGNIFICANCE: In the ever-transforming landscape of regenerative medicine, the embracing of engineered bioabsorbable surgical meshes stands as a key milestone in addressing persistent challenges and complications associated with existing treatments. The urgency to move beyond conventional non-absorbable meshes, fraught with post-surgery complications, emphasises the necessity of using advanced biomaterials for engineered tissue regeneration. This review critically examines the growing field of absorbable surgical meshes, considering their potential to transform clinical practice. By strategically combining mechanical strength with bioresorbable characteristics, these innovative meshes hold the promise of mitigating complications and improving patient outcomes across diverse medical applications. As we navigate the complexities of modern medicine, this exploration of engineered absorbable meshes emerges as a promising approach, offering an overall perspective on biomaterials, technologies, and strategies adopted to redefine the future of surgical meshes.

The Physiological Inorganic Polymers Biosilica and Polyphosphate as Key Drivers for Biomedical Materials in Regenerative Nanomedicine

There is a need for novel nanomaterials with properties not yet exploited in regenerative nanomedicine. Based on lessons learned from the oldest metazoan phylum, sponges, it has been recognized that two previously ignored or insufficiently recognized principles play an essential role in tissue regeneration, including biomineral formation/repair and wound healing. Firstly, the dependence on enzymes as a driving force and secondly, the availability of metabolic energy. The discovery of enzymatic synthesis and regenerative activity of amorphous biosilica that builds the mineral skeleton of siliceous sponges formed the basis for the development of successful strategies for the treatment of osteochondral impairments in humans. In addition, the elucidation of the functional significance of a second regeneratively active inorganic material, namely inorganic polyphosphate (polyP) and its amorphous nanoparticles, present from sponges to humans, has pushed forward the development of innovative materials for both soft (skin, cartilage) and hard tissue (bone) repair. This energy-rich molecule exhibits a property not shown by any other biopolymer: the delivery of metabolic energy, even extracellularly, necessary for the ATP-dependent tissue regeneration. This review summarizes the latest developments in nanobiomaterials based on these two evolutionarily old, regeneratively active materials, amorphous silica and amorphous polyP, highlighting their specific, partly unique properties and mode of action, and discussing their possible applications in human therapy. The results of initial proof-of-concept studies on patients demonstrating complete healing of chronic wounds are outlined.

Cytotoxicity studies and antibacterial modification of poly(ethylene 2,5-furandicarboxylate) nonwoven

Novel poly(ethylene 2,5-furandicarboxylate) PEF nonwovens were produced by solution electrospinning and further modification. To improve the wettability of the hydrophobic nonwovens with water, they were treated with sodium hydroxide. Cytotoxicity tests carried out with human keratinocytes confirmed that the nonwovens did not have a toxic effect on healthy cells. The hydrophilicity of the sodium hydroxide treated nonwoven favored the adherence of the cells and their growth. In turn, the two-step modification of the nonwovens by reactions with (3-mercaptopropyl)methyldimethoxysilane and silver nitrate permitted to deposit silver particles on the fiber surfaces. The bacteria growth inhibition zones around the tested specimens were observed evidencing their antibacterial activity against Escherichia coli and Staphylococcus aureus.

Abdominal wall hernia repair: from prosthetic meshes to smart materials

Hernia reconstruction is one of the most frequently practiced surgical procedures worldwide. Plastic surgery plays a pivotal role in reestablishing desired abdominal wall structure and function without the drawbacks traditionally associated with general surgery as excessive tension, postoperative pain, poor repair outcomes, and frequent recurrence. Surgical meshes have been the preferential choice for abdominal wall hernia repair to achieve the physical integrity and equivalent components of musculofascial layers. Despite the relevant progress in recent years, there are still unsolved challenges in surgical mesh design and complication settlement. This review provides a systemic summary of the hernia surgical mesh development deeply related to abdominal wall hernia pathology and classification. Commercial meshes, the first-generation prosthetic materials, and the most commonly used repair materials in the clinic are described in detail, addressing constrain side effects and rational strategies to establish characteristics of ideal hernia repair meshes. The engineered prosthetics are defined as a transit to the biomimetic smart hernia repair scaffolds with specific advantages and disadvantages, including hydrogel scaffolds, electrospinning membranes, and three-dimensional patches. Lastly, this review critically outlines the future research direction for successful hernia repair solutions by combing state-of-the-art techniques and materials.

Orally Administrable H2 S-Scavenging Metal-Organic Framework Prepared by Co-Flow Microfluidics for Comprehensive Restoration of Intestinal Milieu

Intestinal milieu disorders are strongly related to the occurrence of inflammatory bowel diseases (IBDs), which results from mucosa destruction, epithelium disruption, and tight junction (TJ) proteins loss. Excess of H₂ S in the intestinal milieu produced by the sulfate-reducing bacteria metabolism contributes to development of IBDs via epithelial barrier breakdown. Conventional interventions, such as surgery and anti-inflammatory medications, are considered not completely effective because of frequent recurrence and other complications. Herein, a novel oral delivery system, a hydroxypropyl methylcellulose acetate succinate (HPMCAS)-based polymer-coated Zr-based metal-organic framework (UiO-66) with a Cu_x -rhodamine B (CR) probe (hereinafter referred to as HUR), is produced via a co-flow microfluidic approach with the ability to reduce H₂ S levels, thus restoring the intestinal lumen milieu. HPMCAS serves as an enteric coating that exposes UiO-66@CR at the pH of the intestine but not the acidic pH of the stomach. The synthesized HUR exhibits notable therapeutic efficacy, including mucosa recovery, epithelium integrity restoration, and TJ proteins upregulation via H₂ S scavenging to protect against intestinal barrier damage and microbiome dysbiosis. Thus, HUR is verified to be a promising theranostic platform able to decrease the H₂ S content for intestinal milieu disorder treatment. The presented study therefore opens the door for further exploitation for IBDs therapy.

Biomimetic Polyphosphate Materials: Toward Application in Regenerative Medicine

In recent years, inorganic polyphosphate (polyP) has attracted increasing attention as a biomedical polymer or biomaterial with a great potential for application in regenerative medicine, in particular in the fields of tissue engineering and repair. The interest in polyP is based on two properties of this physiological polymer that make polyP stand out from other polymers: polyP has morphogenetic activity by inducing cell differentiation through specific gene expression, and it functions as an energy store and donor of metabolic energy, especially in the extracellular matrix or in the extracellular space. No other biopolymer applicable in tissue regeneration/repair is known that is endowed with this combination of properties. In addition, polyP can be fabricated both in the form of a biologically active coacervate and as biomimetic amorphous polyP nano/microparticles, which are stable and are activated by transformation into the coacervate phase after contact with protein/body fluids. PolyP can be used in the form of various metal salts and in combination with various hydrogel-forming polymers, whereby (even printable) hybrid materials with defined porosities and mechanical and biological properties can be produced, which can even be loaded with cells for 3D cell printing or with drugs and support the growth and differentiation of (stem) cells as well as cell migration/microvascularization. Potential applications in therapy of bone, cartilage and eye disorders/injuries and wound healing are summarized and possible mechanisms are discussed.

Filament-anchored hydrogel layer on polypropylene hernia mesh with robust anti-inflammatory effects

The efficacy of implanted polypropylene (PP) hernia meshes is often compromised by an inflammatory response. Thus, engineering an anti-inflammatory mesh has significant implications for hernioplasty. Here, we report a facile strategy to develop a filament-anchored hydrogel layer (FAHL) on PP mesh (FAHL-P). The network of FAHL, made up of chondroitin sulfate and gelatin (CG), provided a biomimetic surface with immunoregulatory properties. The use of tannic acid (TA) as a crosslinker for CG additionally enhanced its anti-inflammatory properties. In addition, the fabrication protocol ensured that the hydrogel maintained the properties of the knitted mesh and the firmly adherent FAHL during general handling (dry state) and in the simulated body environment (wet state). CG/TA-PP killed 99.99% of S. aureus and retained 73% of its original antioxidant properties after 7 d. The FAHL durably performed with a controlled release of TA for 15 d. The strong anti-inflammatory effects of FAHL-P reduced collagen deposition and increased vascularization, which promoted native tissue generation. The fabrication strategy has potential applications in hernioplasty and may provide new insights into the design of other anti-inflammatory implants. STATEMENT OF SIGNIFICANCE: A hydrogel layer with robust anti-inflammatory effects was anchored firmly on mesh filament for hernia repair. Requiring no drug loading, this chondroitin sulphate -gelatin (CG) based hydrogel itself could inhibit the immunological attack owing to the biomimetic microenvironment created by the CG. Moreover, the hydrogel's crosslinker (tannic acid) content served as an effective scavenger for reducing pro-inflammatory factors, significantly mitigating the inflammation. Interestingly, the antibacterial effect of such hydrogel layer was also observed. In terms of the synergistic outcome of the design, our mesh can remarkably attenuate inflammation and promote constructive tissue regeneration in vivo. Furthermore, considering the relatively simple and easily scaled up formulation process, our strategy may indeed have great potential in alleviating post-implantation outcomes.

Functionalized Strategies and Mechanisms of the Emerging Mesh for Abdominal Wall Repair and Regeneration

Meshes have been the overwhelmingly popular choice for the repair of abdominal wall defects to retrieve the bodily integrity of musculofascial layer. Broadly, they are classified into synthetic, biological and composite mesh based on their mechanical and biocompatible features. With the development of anatomical repair techniques and the increasing requirements of constructive remodeling, however, none of these options satisfactorily manages the conditional repair. In both preclinical and clinical studies, materials/agents equipped with distinct functions have been characterized and applied to improve mesh-aided repair, with the importance of mesh functionalization being highlighted. However, limited information exists on systemic comparisons of the underlying mechanisms with respect to functionalized strategies, which are fundamental throughout repair and regeneration. Herein, we address this topic and summarize the current literature by subdividing common functions of the mesh into biomechanics-matched, macrophage-mediated, integration-enhanced, anti-infective and antiadhesive characteristics for a comprehensive overview. In particular, we elaborate their effects separately with respect to host response and integration and discuss their respective advances, challenges and future directions toward a clinical alternative. From the vastly different approaches, we provide insight into the mechanisms involved and offer suggestions for personalized modifications of these emerging meshes.

Bacterial biopolymers: from pathogenesis to advanced materials

Bacteria are prime cell factories that can efficiently convert carbon and nitrogen sources into a large diversity of intracellular and extracellular biopolymers, such as polysaccharides, polyamides, polyesters, polyphosphates, extracellular DNA and proteinaceous components. Bacterial polymers have important roles in pathogenicity, and their varied chemical and material properties make them suitable for medical and industrial applications. The same biopolymers when produced by pathogenic bacteria function as major virulence factors, whereas when they are produced by non-pathogenic bacteria, they become food ingredients or biomaterials. Interdisciplinary research has shed light on the molecular mechanisms of bacterial polymer synthesis, identified new targets for antibacterial drugs and informed synthetic biology approaches to design and manufacture innovative materials. This Review summarizes the role of bacterial polymers in pathogenesis, their synthesis and their material properties as well as approaches to design cell factories for production of tailor-made bio-based materials suitable for high-value applications.

Utilization of metabolic energy in treatment of ocular surface disorders: polyphosphate as an energy source for corneal epithelial cell proliferation

Impaired regeneration of the corneal epithelium, as found in many ocular surface diseases, is a major clinical problem in ophthalmology. We hypothesized that corneal epithelial regeneration can be promoted by the physiological, energy-delivering as well as "morphogenetically active" polymer, inorganic polyphosphate (polyP). Corneal limbal explants (diameter, 4 mm) were cultivated on collagen-coated well plates in the absence or presence of polyP (chain length, ∼40 Pi units; 50 μg ml-1) or human platelet lysate (hp-lysate; 5% v/v). Cell outgrowth and differentiation were analyzed after staining with DRAQ5 (nuclei) and rhodamine phalloidin (cytoskeleton), as well as by environmental scanning electron microscopy (ESEM). Cell growth/viability of hCECs was assessed by XTT assay. The expression of SDF-1 was quantitated by qRT-PCR. Exposure to hp-lysate (also containing polyP) increased cell migration already at day 1. Even stronger was the effect of polyP. This effect was blocked by a mast cell serine protease. The formation of cell multilayers was enhanced by hp-lysate or even more by polyP. ESEM revealed continuous cell junctions and prominent microvilli on the surface of adjacent cells exposed to polyP; those structures were only rarely seen in the controls. The hp-lysate and, more potently, polyP increased the proliferation of hCECs, as well as SDF-1 expression. The findings indicate the potential usefulness of the natural polymer, polyP, for topical treatment of corneal epithelial defects. Future studies are directed to develop suitable formulations of polyP, such as biomimetic polyP nano/microparticles showing an adjustable release kinetics.

Amorphous polyphosphate, a smart bioinspired nano-/bio-material for bone and cartilage regeneration: towards a new paradigm in tissue engineering

Physiological amorphous polyphosphate nano/micro-particles, injectable and implantable, attract and stimulate MSCs into implants for tissue regeneration.