Polysaccharide-based films for the prevention of unwanted postoperative adhesions at biological interfaces

Recent advances in smart hydrogels derived from polysaccharides and their applications for wound dressing and healing

Owing to their inherent biocompatibility and biodegradability, hydrogels derived from polysaccharides have emerged as promising candidates for wound management. However, the complex nature of wound healing often requires the development of smart hydrogels---intelligent materials capable of responding dynamically to specific physical or chemical stimuli. Over the past decade, an increasing number of stimuli-responsive polysaccharide-based hydrogels have been developed to treat various types of wounds. While a range of hydrogel types and their versatile functions for wound management have been discussed in the literature, there is still a need for a review of the crosslinking strategies used to create smart hydrogels from polysaccharides. This review provides a comprehensive overview of how stimuli-responsive hydrogels can be designed and made using five key polysaccharides: chitosan, hyaluronic acid, alginate, dextran, and cellulose. Various methods, such as chemical crosslinking, dynamic crosslinking, and physical crosslinking, which are used to form networks within these hydrogels, ultimately determine their ability to respond to stimuli, have been explored. This article further looks at different polysaccharide-based hydrogel wound dressings that can respond to factors such as reactive oxygen species, temperature, pH, glucose, light, and ultrasound in the wound environment and discusses how these responses can enhance wound healing. Finally, this review provides insights into how stimuli-responsive polysaccharide-based hydrogels can be developed further as advanced wound dressings in the future.

Janus decellularized membrane with anisotropic cell guidance and anti-adhesion silk-based coatings for spinal dural repair

The repair of soft tissues with anisotropic structures, such as spinal dura mater, requires the use of biomaterials to guide tissue directional growth while minimizing epidural fibrotic adhesion. Herein, we construct the Janus small intestinal submucosa (SIS) via silk-based hydrogel coatings, which provides extracellular matrix-mimicking features and anti-adhesion performance for spinal dural defect repair. We demonstrate that the silk fibroin and methacrylated silk fibroin (SilMA) composite microgroove hydrogel coating at the inner surface via water vapor annealing treatment exhibits excellent structure stability, stable attachment to SIS substrate, and shows orientated cell morphology and extracellular matrix produced by fibroblasts, good histocompatibility and promotes the polarization of macrophages towards the anti-inflammatory phenotype. The methacrylated hyaluronic acid and SilMA composite coating outer surface serves as favorable physical barrier shows effective resistance to protein adsorption, cell and tissue adhesion, and can mitigate fibrosis reactions. Spinal dura mater defect experiments on male rats demonstrate that the Janus SIS simultaneously promotes dural regeneration and inhibits epidural fibrosis.

Research progress on animal models of peritoneal adhesion

Peritoneal adhesion is a common complication of abdominal and pelvic surgery that can cause various clinical symptoms, including abdominal pain, intestinal obstruction, and female infertility, significantly impacting patient quality of life. Animal models of peritoneal adhesion are important tools for studying the mechanisms of adhesion formation and evaluating the effectiveness of prevention and treatment. Various methods for constructing animal models of peritoneal adhesion include physical injury, chemical injury, ischemia, infection, foreign body stimulation, and simulated surgery; however, none can fully simulate peritoneal adhesion in patients clinically. Therefore, this review aimed to explore previous methods used to construct peritoneal adhesion animal models and summarize their principles, characteristics, and applications. Similarly, it summarizes macroscopic and microscopic evaluation indicators, such as peritoneal adhesion gross assessment, histological scoring, and molecular markers. On the basis of this, we proposed a new animal model of peritoneal adhesion that simulates the factors contributing to peritoneal adhesion formation in clinical surgery. peritoneal adhesion formation was stable and standardized using our proposed model, providing a foundation for the establishment and application of peritoneal adhesion animal models.

Urological Applications of Novel Hyaluronic Acid/Alginate Gel to Protect Nerves: A Single-Surgeon Experience

Background Tissue gliding and mobility are crucial for the success of penile procedures, as postoperative adhesions can lead to painful tethering of tissues, including nerves. While most commercially available options are not designed to reduce friction and/or often have inconsistent bioresorption, a novel hyaluronic acid/alginate hydrogel represents a significant advancement in reducing postoperative tissue adhesions. This study aimed to evaluate its intra-operative application in pediatric and adult urologic surgeries with associated indications and postoperative outcomes (re-admission, re-operation, complications). Methods A retrospective review of 142 male patients undergoing urologic procedures by a single surgeon between October 1, 2022, and October 1, 2023, was conducted after IRB approval. The hydrogel was applied intra-operatively at the surgical site prior to closure. Data on demographics, preoperative diagnoses, and postoperative outcomes were extracted from a prospectively maintained registry and verified through chart review. Diagnoses included 376 conditions such as penoscrotal webbing, hidden penis, and phimosis. Outcomes, including complications, readmissions, and reoperations, were evaluated over an eight-week follow-up period. Descriptive statistics summarized the data and visual tools were used for analysis. Results The cohort comprised 142 male patients, predominantly pediatric (93.7%), with the majority (60.0%) under 1 year of age. A total of 376 urologic diagnoses were recorded, with the most frequent being penoscrotal webbing (94 cases, 25.0%), hidden penis (73 cases, 19.4%), and phimosis of the penis (61 cases, 16.2%). Less common diagnoses included hypospadias (6 cases, 1.6%) and various rare conditions with a frequency of 0.27%. Postoperative outcomes showed no complications, re-admissions, or re-operations among the entire patient cohort. Conclusion Intra-operative application of a hyaluronic acid/alginate hydrogel in pediatric and adult urologic procedures demonstrates its safety and potential utility in minimizing postoperative tissue adhesions and complications. Further study is warranted to confirm these findings and explore additional applications of this material.

Bioinspired Janus Mesh with Mechanical Support and Side-specific Biofunctions for Hernia Repair

Postoperative adhesion (PA) caused by the combination of proteins, inflammatory response and bacterial infection poses substantial challenges for polypropylene meshes (PPMs) based hernioplasty. Herein, inspired by the peritoneum, a Janus PPMs with side-specific functions was developed via a surface-initiated photoiniferter-mediated polymerization technology. A physical barrier composed of zwitterionic polymer brushes (PS) was firstly constructed on the one side of the PPMs, while the polymethacrylic acid (PMAA) brushes acting as the linker for bioactive nanoparticles (HAP) were precisely situated on the opposite surface subsequently. Our findings reveal that the mesh surface modified with PS demonstrated significant antifouling property that more than 99% of protein adhesion could be inhibited even after the co-incubation for 72 h in the crucial test. Meanwhile, on the other surface of the PPMs modified with HAP achieved satisfactory ROS-scavenging, inflammation-inhibiting and cell adhesion-promoting properties as well as good bactericidal performance (killing rate > 99.9%). Furthermore, the Janus PPMs could maintain comparable mechanical property with pristine meshes. Equipped with the above multiple merits and asymmetric property, the constructed Janus PPMs demonstrated effective treatment for abdominal hernia defects in vivo without any PA formation. Overall, this study duplicates the unique characteristics of peritoneum onto PPMs to successfully address postoperative complications of the hernioplasty and also offers a versatile and innovative idea to construct asymmetrical functions on the one implant. STATEMENT OF SIGNIFICANCE: The implantation of surgical meshes in the hernia defect provides additional firm support to reinforce the abdomen fascia in tension-free way. However, multiple post-surgery complications induced tissue adhesions is of great challenges for commercial mesh-based hernioplasty. Although material designing and surface modification might circumvent these limitations partly, the construction of side-specific biofunctions on the commercial mesh surfaces is very challenging because of its porous structure. Herein, we demonstrate a feasible and promising approach to construct asymmetric biofunctions on the opposite sides of network structured polypropylene mesh, which is rarely achieved previously. The fabricated Janus PPMs maintains the inherent long-term mechanical support; meanwhile, the opposite sides of PPMs could perform multiple biofunctions independently.

A Novel Urological Application of Hyaluronic Acid/Alginate Sheet to Prevent Adhesion Formation: A Technique Guide and Case Series

Tissue gliding and mobility are paramount to the success of penile procedures. While postoperative healing is intended to protect, repair, and nourish injured tissues, an overzealous response often leaves painful and debilitating tethering between the corpora, including nerves, and surrounding tissues. This tethering interferes with the intended outcomes of surgery by preventing necessary gliding. An ideal implant that serves as a tissue gliding companion would be an easy-to-apply, temporary gliding surface that prevents unwanted tethering, bioresorbs completely, and flexibly addresses tissues that significantly contract postoperatively. Unfortunately, most commercially available options are difficult to use intra-operatively, are not designed to reduce friction, have variable efficacy, and have incomplete bioresorption. A promising new technology is a hydrogel made from alginate and hyaluronic acid (HA). Application of this hydrogel is revolutionizing orthopedic hand surgery, spine surgery, sports injury repair, and foot and ankle surgery with placement of gel/sheets around a range of soft tissue environments (joints, tendons, ligaments, peripheral nerves, vasculature) without issue. We present a case series of four patients undergoing various urologic procedures with the application of this novel bioresorbable hydrogel and their associated excellent clinical outcomes with no adverse events. We also discuss potential urologic indications for the use of this bioresorbable hydrogel along with technical intra-operative considerations.

Janus-Structured Microgel Barrier with Tissue Adhesive and Hemostatic Characteristics for Efficient Prevention of Postoperative Adhesion

Postoperative adhesion (POA) is a common and serious complication following various types of surgery. Current physical barriers either have a short residence time at the surgical site with a low tissue attachment capacity or are prone to undesired adhesion formation owing to the double-sided adhesive property, which limits the POA prevention efficacy of the barriers. In this study, Janus-structured microgels (Janus-MGs) with asymmetric tissue adhesion capabilities are fabricated using a novel bio-friendly gas-shearing microfluidic platform. The anti-adhesive side of Janus-MGs, which consists of alginate, hyaluronic acid, and derivatives, endows the material with separation, lubrication, and adhesion prevention properties. The adhesive side provided Janus-MGs with tissue attachment and retention capability through catechol-based adhesion, thereby enhancing the in situ adhesion prevention effect. In addition, Janus-MGs significantly reduced blood loss and shortened the hemostatic time in rats, further reducing adhesion formation. Three commonly used rat POA models with different tissue structures and motion patterns are established in this study, namely peritoneal adhesion, intrauterine adhesion, and peritendinous adhesion models, and the results showed that Janus-MGs effectively prevented the occurrence of POA in all the models. The fabrication of Janus-MGs offers a reliable strategy and a promising paradigm for preventing POA following diverse surgical procedures.

A biodegradable shape memory polyurethane film as a postoperative anti-adhesion barrier for minimally invasive surgery

Postoperative adhesions commonly form in various tissues, resulting in serious implications and an increased risk of secondary surgery. The application of anti-adhesion films as physical barriers has proven effective in reducing adhesion incidence and severity. However, existing anti-adhesion films require manual deployment during minimally invasive surgery, posing inconvenience and possibility of further injury. To address these limitations, we have developed an intelligent anti-adhesion film based on shape memory polyurethane. In this work, a linear shape memory polyurethane (ISO2-PU), incorporating hexamethylene isocyanate and isosorbitol as hard segments and poly(D, L-lactic acid) macrodiol as soft segments, was fabricated into an anti-adhesion film. The favorable shape memory effect of the ISO2-PU film ensures its convenient delivery and automatic unfolding, as revealed by a simulation experiment for endoscopic surgical implantation. Furthermore, the glass transition temperature (Tg) close to body temperature endows the ISO2-PU film with good mechanical compliance, thus ensuring a reliable fit with the wounded tissue to avoid undesired folding. Finally, in vivo experiments using a rat cecal abdominal wall injury model demonstrated that the combination of reliable fit, appropriate degradation rate, and good cytocompatibility promises the ISO2-PU film with high anti-adhesion efficacy. This work validates the concept of shape memory anti-adhesion barrier and expands future directions for advanced anti-adhesion biomaterials. STATEMENT OF SIGNIFICANCE: Postoperative adhesions are a common complication that occurs widely after various surgeries. This work developed an intelligent anti-adhesion film based on a linear shape memory polyurethane (ISO2-PU). This film is featured with remarkable shape memory effect and mechanical compliance at body temperature, appropriate degradability, and good cytocompatibility. These merits ensure convenient delivery and smart unfolding of ISO2-PU film during minimally invasive surgery and favorable postoperative anti-adhesion efficacy. The results validate the concept of shape memory anti-adhesion barrier and paves a way for designing next-generation anti-adhesion biomaterials.

Polysaccharide-based emulsion gels for the prevention of postoperative adhesions and as a drug delivery system using 5-fluorouracil

Postoperative tissue adhesion is a well-recognized and common complication. Despite ongoing developments in anti-adhesion agents, complete prevention remains a challenge in clinical practice. Colorectal cancer necessitates both adhesion prevention and postoperative chemotherapy. Accordingly, drug-loading into an anti-adhesion agent could be employed as a treatment strategy to maximize the drug effects through local application and minimize side effects. Herein, we introduce an anti-adhesion agent that functions as a drug delivery system by loading drugs within an emulsion that forms a gel matrix in the presence of polysaccharides, xanthan gum, and pectin. Based on the rheological analysis, the xanthan gum-containing emulsion gel formed a gel matrix with suitable strength and mucosal adhesiveness. In vitro dissolution tests demonstrated sustained drug release over 12 h, while in vivo pharmacokinetic studies revealed a significant increase in the Tmax (up to 4.03 times) and area under the curve (up to 2.62 times). However, most of the drug was released within one day, distributing systemically and raising toxicity concerns, thus limiting its efficacy as a controlled drug delivery system. According to in vivo anti-adhesion efficacy evaluations, the xanthan gum/pectin emulsion gels, particularly F2 and F3, exhibited remarkable anti-adhesion capacity (P < 0.01). The emulsion gel formulation exhibited no cytotoxicity against fibroblasts or epithelial cell lines. Thus, the xanthan gum/pectin emulsion gel exhibits excellent anti-adhesion properties and could be developed as a drug delivery system.

Nonswellable Hydrogel Patch with Tissue-Mimetic Mechanical Characteristics Remodeling In Vivo Microenvironment for Effective Adhesion Prevention

Postoperative adhesion is a common complication after abdominal surgery, but current clinical products have unsatisfactory therapeutic effects. Here, we present a hydrogel patch formed in a single step through dialysis. The exchange of DMSO into water facilitates hydrophobic aggregate in situ formation and the formation of hydrogen bonds within the hydrogel. Thanks to the optimized component ratio and precise structural design. The hydrogel patch has soft-tissue-like mechanical characteristics, including high strength, high toughness, low modulus similar to the abdominal wall, good fatigue resistance, and fast self-recovery properties. The nonswellable hydrogel patch retains over 80% of its original mechanical properties after 7 days of immersion in physiological saline, with a maximum swelling ratio of 5.6%. Moreover, the hydrophobic biomultifunctionality of benzyl isothiocyanate can self-assemble onto the hydrogel patch during the sol-gel transition process, enabling it to remodel the inflammatory microenvironment through synergistic antibacterial, antioxidant, and anti-inflammatory effects. The hydrogel patch prevents postsurgical adhesion in a rat sidewall defect-cecum abrasion model and outperforms the leading commercial Interceed. It holds promising potential for clinical translation, considering that FDA-approved raw materials (PVA and gelatin) form the backbone of this effective hydrogel patch.

Advanced postoperative tissue antiadhesive membranes enabled with electrospun nanofibers

Tissue adhesion is one of the most common postoperative complications, which is frequently accompanied by inflammation, pain, and even dyskinesia, significantly reducing the quality of life of patients. Thus, to prevent the formation of tissue adhesions, various strategies have been explored. Among these methods, placing anti-adhesion membranes over the injured site to separate the wound from surrounding tissues is a simple and prominently favored method. Recently, electrospun nanofibers have been the most frequently investigated antiadhesive membranes due to their tunable porous structure and high porosities. They not only can act as an essential barrier and functional carrier system but also allow for high permeability and nutrient transport, showing great potential for preventing tissue adhesion. Herein, we provide a short review of the most recent applications of electrospun nanofibrous antiadhesive membranes in tendons, the abdominal cavity, dural sac, pericardium, and meninges. Firstly, each section highlights the most representative examples and they are sorted based on the latest progress of related research. Moreover, the design principles, preparation strategies, overall performances, and existing problems are highlighted and evaluated. Finally, the current challenges and several future ways to develop electrospun nanofibrous antiadhesive membranes are proposed. The systematic discussion and proposed directions can shed light on ideas and guide the reasonable design of electrospun nanofibrous membranes, contributing to the development of exceptional tissue anti-adhesive materials in the foreseeable future.

Chitosan-crosslinked polyvinyl alcohol anti-swelling hydrogel designed to prevent abdominal wall adhesion

Abdominal adhesion is a frequent clinical issue with a high incidence rate and consequences following intra-abdominal surgery. Although many anti-adhesion materials have been used in surgical procedures, additional research is still needed to determine which ones have the most robust wet tissue adhesion, the best anti-postoperative adhesion, and the best anti-inflammatory properties. We have developed an excellent tissue adhesion and anti-swelling polyvinyl alcohol-chitosan hydrogel (AS hydrogel). According to in vitro cell testing, AS hydrogel significantly decreased inflammation around cells and exhibited good biocompatibility. Further, we assessed how well AS hydrogel prevented intraperitoneal adhesion using a rabbit model with cecum and abdominal wall injuries. According to the data, AS hydrogel has excellent anti-inflammatory and biodegradability properties compared to the control group. It can also prevent intestinal and abdominal wall injuries from occurring during surgery. Based on these results, hydrogel appears to be a perfect new material to prevent postoperative abdominal wall adhesion.

Effect of multi arm-PEG-NHS (polyethylene glycol n-hydroxysuccinimide) branching on cell adhesion to modified decellularized bovine and porcine pericardium

Implanting physical barrier materials to separate wounds from their surroundings is a promising strategy for preventing postoperative adhesions. Herein, we develop a material that switches from an anti-adhesive surface to an adhesive surface, preventing adhesion in the early stage of transplantation and then promoting recellularization. In this study, 2-arm, 4-arm, and 8-arm poly(ethylene glycol) succinimidyl glutarate (2-, 4-, 8-arm PEG-NHS) were used to modify the surface of decellularized porcine and bovine pericardium. The number of free amines on the surface of each material significantly decreased following modification regardless of the reaction molar ratio of NH2 and NHS, the number of PEG molecule branches, and the animal species of the decellularized tissue. The structure and mechanical properties of the pericardium were maintained after modification with PEG molecules. The time taken for the PEG molecules to detach through hydrolysis of the ester bonds differed between the samples, which resulted in different cell repulsion periods. By adjusting the reaction molar ratio, the number of PEG molecule branches, and the animal species of the decellularized pericardium, the duration of cell repulsion can be controlled and is expected to provide an anti-adhesion material for a variety of surgical procedures.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Improving the Physical Properties of Starch-Based Powders for Potential Anti-Adhesion Applications

Postoperative adhesion is one of the most common complications that occur during and after surgery; thus, materials that can prevent adhesion are often applied. Starch powders with a high water absorption capacity are preferred, and many studies have focused on increasing the water absorption of modified starches, as native starch powders display poor water-holding capacities. The effects of salts on the physical properties of acetylated distarch phosphate potato starch powders were investigated here. Changes in functional groups, the crystal structures of modified starch, particle morphologies, water absorption, viscosity, and in vivo adhesion were investigated. The results showed that salts greatly improved the water absorption and viscosity of acetylated distarch phosphate potato starch powders. Among the three different salt-modified starch powders, NaCl-modified starch powders displayed higher water absorption and viscosity and demonstrated better in vivo anti-adhesion performance. The results of this study propose a potential biomaterial that may function as an anti-adhesive, potentially leading to reduced surgical risks and a better quality of life for patients.

A Zwitterionic Hydrogel with Anti-Oxidative and Anti-Inflammatory Properties for the Prevention of Peritoneal Adhesion by Inhibiting Mesothelial-Mesenchymal Transition

Postoperative peritoneal adhesion is a serious clinical complication. Various hydrogel barriers have been developed to prevent peritoneal adhesion. However, it remains a challenge to design a hydrogel with desirable physicochemical properties and bioactivities. In this study, a zwitterionic polysaccharide-based multifunctional hydrogel is developed using epigallocatechin-3-gallate (EGCG) to prevent postoperative abdominal adhesion. This hydrogel is simple to use and has desirable properties, such as excellent injectability, self-healing, and non-swelling properties. The hydrogel also has ultralow fouling capabilities, such as superior bactericidal performance, cell and protein adhesion, and low immunogenicity resistance. Moreover, the hydrogel exhibits good antioxidant activity, which is attributed to the integration of EGCG. Furthermore, the detailed mechanism from in vivo and in vitro experimental studies illustrates that hydrogel compositions can synergistically prevent adhesion formation through multiple pathways, including anti-inflammatory and antioxidant capabilities and inhibition effects on the mesothelial-mesenchymal transition (MMT) process induced by transforming growth factor (TGF-β). In summary, this zwitterionic multifunctional hydrogel has great potential to prevent postoperative adhesion formation in the clinical setting.

Cyclical endometrial repair and regeneration: Molecular mechanisms, diseases, and therapeutic interventions

The endometrium is a unique human tissue with an extraordinary ability to undergo a hormone-regulated cycle encompassing shedding, bleeding, scarless repair, and regeneration throughout the female reproductive cycle. The cyclical repair and regeneration of the endometrium manifest as changes in endometrial epithelialization, glandular regeneration, and vascularization. The mechanisms encompass inflammation, coagulation, and fibrinolytic system balance. However, specific conditions such as endometriosis or TCRA treatment can disrupt the process of cyclical endometrial repair and regeneration. There is uncertainty about traditional clinical treatments' efficacy and side effects, and finding new therapeutic interventions is essential. Researchers have made substantial progress in the perspective of regenerative medicine toward maintaining cyclical endometrial repair and regeneration in recent years. Such progress encompasses the integration of biomaterials, tissue-engineered scaffolds, stem cell therapies, and 3D printing. This review analyzes the mechanisms, diseases, and interventions associated with cyclical endometrial repair and regeneration. The review discusses the advantages and disadvantages of the regenerative interventions currently employed in clinical practice. Additionally, it highlights the significant advantages of regenerative medicine in this domain. Finally, we review stem cells and biologics among the available interventions in regenerative medicine, providing insights into future therapeutic strategies.

What is the impact of intraperitoneal surfactant administration against postoperative intraabdominal adhesion formation? an experimental study

Background/Aim

Surfactant is a surface-active substance that, in addition to its detergent effect, also has effects that reduce inflammation and fibrosis. Because of these effects, it was aimed herein to investigate the effect of intraperitoneal surfactant application on preventing postoperative peritoneal adhesion formation in a uterine horn adhesion model.

Materials and methods

Twenty-one Wistar albino rats were randomly divided into 3 groups (G1-G3), as follows: G1 (n = 7): control group. The abdomen was opened and then closed; G2 (n = 7): adhesion group. The abdomen was opened. Then, a 2-cm linear incision was made over the right uterine horn, 2 mL of isotonic saline was administered intraperitoneally, and the abdomen was closed; and G3 (n = 7): treatment group. The abdomen was opened, a 2-cm linear incision was made over the right uterine horn, 2 mL (70 mg/kg) of surfactant was administered intraperitoneally, and the abdomen was closed. After 15 days, the rats were euthanized, the abdomens were reopened, and adhesion scoring was performed. After the right uterine horns were removed and fixed with 10% formalin, appropriate sections were taken from the traumatized tissue, stained with Masson's trichrome, and fibrosis and inflammation scoring were performed.

Results

The adhesion area and intensity were significantly higher in G2 than in G1 and G3 (p = 0.001) and were similar in G1 and G3 (p = 0.165). While fibrosis and inflammation were significantly higher in G2 than in G1 and G3 (p = 0.001), there was no difference between G1 and G3 (p = 0.5).

Conclusion

Intraperitoneal surfactant administration at a dose of 70 mg/kg was found to be effective in preventing intraabdominal adhesion formation in a rat uterine horn model.

The Antimicrobial, Hemostatic, and Anti-Adhesion Effects of a Peptide Hydrogel Constructed by the All-d-Enantiomer of Antimicrobial Peptide Jelleine-1

Peptide hydrogels are believed to be potential biomaterials with wide application in the biomedical field because of their good biocompatibility, injectability, and 3D printability. Most of the previously reported polypeptide hydrogels are composed of l-peptides, while the hydrogels formed by self-assembly of d-peptides are rarely reported. Herein, a peptide hydrogel constructed by D-J-1, which is the all-d-enantiomer of antimicrobial peptide Jelleine-1 (J-1) is reported. Field emission scanning electron microscope (FE-SEM) and rheologic study are performed to characterize the hydrogel. Antimicrobial, hemostatic, and anti-adhesion studies are carried out to evaluate its biofunction. The results show that D-J-1 hydrogel is formed by self-assembly and cross-linking driven by hydrogen bonding, hydrophobic interaction, and π-π stacking force of aromatic ring in the structure of D-J-1. It exhibits promising antimicrobial activity, hemostatic activity, and anti-adhesion efficiency in a rat sidewall defect-cecum abrasion model. In addition, it also exhibits good biocompatibility. Notably, D-J-1 hydrogel shows improved in vitro and in vivo stability when compared with its l-enantiomer J-1 hydrogel. Therefore, the present study will provide new insight into the application of d-peptide hydrogel, and provides a new peptide hydrogel with antibacterial, hemostatic, and anti-adhesion efficacy for clinical use.

Multifunctional calcium polyphenol networks reverse the hostile microenvironment of trauma for preventing postoperative peritoneal adhesions

Abdominal adhesions, a commonly observed complication of abdominal surgery, have a high incidence and adversely affect patients' physical and mental health. The primary causes of abdominal adhesions are intraoperative trauma, acute inflammatory response, bleeding, and foreign body infection. Because most current treatment approaches for abdominal adhesions are limited, improved and novel postoperative anti-adhesion regimens are urgently needed. In this study, we developed calcium polyphenol network (CaPN) microspheres based on the self-assembly of the natural triphenolic compound gallic acid and Ca2+ in solution. The physicochemical properties of CaPNs, including their hemostatic, antibacterial, antioxidant, and anti-inflammatory activities, were investigated in vitro. Bleeding and cecal-abdominal wall adhesion models were established to observe the hemostatic activity of CaPNs and their preventive effect on postoperative abdominal wall adhesion in vivo. The results showed that CaPNs significantly reduced inflammation, oxidative stress, fibrosis, and abdominal adhesion formation and had good hemostatic and antibacterial properties. Our findings suggest a novel strategy for the prevention of postoperative adhesions.

Degradable carrier-free spray hydrogel based on self-assembly of natural small molecule for prevention of postoperative adhesion

Postoperative peritoneal adhesion (PPA) is frequent and extremely dangerous complication after surgery. Different tactics have been developed to reduce it. However, creating a postoperative adhesion method that is multifunctional, biodegradable, biocompatible, low-toxic but highly effective, and therapeutically applicable is still a challenge. Herein, we have prepared a degradable spray glycyrrhetinic acid hydrogel (GAG) based on natural glycyrrhetinic acid (GA) by straightforward heating and cooling without the use of any additional chemical cross-linking agents to prevent postoperative adhesion. The resultant hydrogel was demonstrated to possess various superior anti-inflammatory activity, and multiple functions, such as excellent degradability and biocompatibility. Specifically, spraying characteristic and excellent antibacterial activities essentially eliminated secondary infections during the administration of drugs in surgical wounds. In the rat models, the carrier-free spray GAG could not only slow-release GA to inhibit inflammatory response, but also serve as physical anti-adhesion barrier to reduce collagen deposition and fibrosis. The sprayed GAG would shed a new light on the prevention of postoperative adhesion and broaden the application of the hydrogels based on natural products in biomedical fields.

Polymer nanomaterials for use as adjuvant surgical tools

Materials employed in the treatment of conditions encountered in surgical and clinical practice frequently face barriers in translation to application. Shortcomings can be generalized through their reduced mechanical stability, difficulty in handling, and inability to conform or adhere to complex tissue surfaces. To overcome an amalgam of challenges, research has sought the utilization of polymer-derived nanomaterials deposited in various fashions and formulations to improve the application and outcomes of surgical and clinical interventions. Clinically prevalent applications include topical wound dressings, tissue adhesives, surgical sealants, hemostats, and adhesion barriers, all of which have displayed the potential to act as superior alternatives to current materials used in surgical procedures. In this review, emphasis will be placed not only on applications, but also on various design strategies employed in fabrication. This review is designed to provide a broad and thought-provoking understanding of nanomaterials as adjuvant tools for the assisted treatment of pathologies prevalent in surgery. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Biocompatible and biodegradable chitin-based hydrogels crosslinked by BDDE with excellent mechanical properties for effective prevention of postoperative peritoneal adhesion

Postoperative peritoneal adhesions are common complications caused by abdominal and pelvic surgery, which seriously impact the quality of life of patients and impose additional financial burdens. Using of biomedical materials as physical barriers to completely isolate the traumatic organ and injured tissue is an optimal strategy for preventing postoperative adhesions. However, the limited efficacy and difficulties in the complete degradation or integration of biomedical materials with living tissues restrict the application of these materials. In this study, novel chitin-based crosslinked hydrogels with appropriate mechanical properties and flexibilities were developed using a facile and green strategy. The developed hydrogels simultaneously exhibited excellent biocompatibilities and resistance to nonspecific protein adsorption and NIH/3T3 fibroblast adhesion. Furthermore, these hydrogels were biodegradable and could be completely integrated into the native extracellular matrix. The chitin-based crosslinked hydrogels also effectively inhibited postoperative peritoneal adhesions in rat models of adhesion and recurrence. Therefore, these novel chitin-based crosslinked hydrogels are excellent candidate physical barriers for the efficient prevention of postoperative peritoneal adhesions and provide a new anti-adhesion strategy for biomedical applications.

From crosslinking strategies to biomedical applications of hyaluronic acid-based hydrogels: A review

Hyaluronic acid (HA) is not only a natural anionic polysaccharide with excellent biocompatibility, biodegradability, and moisturizing effect, but also an essential factor that can affect angiogenesis, inflammation, cell behavior, which has a wide range of applications in the biomedical field. Among them, HA-based hydrogels formed by various physical or chemical crosslinking strategies are particularly striking. They not only retain the physiological function of HA, but also have the skeleton function of hydrogel, which further expands the application of HA. However, HA-based natural hydrogels generally have problems such as insufficient mechanical strength and susceptibility to degradation by hyaluronidase, which limits their application to a certain extent. To solve such problems, researchers have prepared a variety of HA-based multifunctional hydrogels with remarkable properties in recent years by adopting various structural modification methods or novel crosslinking strategies, as well as introducing functionally reactive molecules or moieties, which have extended the application scope. This manuscript systematically introduced common crosslinking strategies of HA-based hydrogels and highlighted the development of novel HA-based hydrogels in anticancer drug delivery, cartilage repair, three-dimensional cell culture, skin dressing and other fields. We hope to provide some references for the subsequent development of HA-based hydrogels in the biomedical field.

Salt sensitive purely zwitterionic physical hydrogel for prevention of postoperative tissue adhesion

Abdominal adhesions are a class of serious complications following abdominal surgery, resulting in a complicated and severe syndrome and sometimes leading to a Gordian knot. Traditional therapies employ hydrogels synthesized using complicated chemical formulations-often with click chemistry or thermal responsive hydrogel. The complicated synthesis process and severe conditions limit the extent of the hydrogels' applications. In this work, poly 3-[2-(methacryloyloxy)ethyl](dimethyl)-ammonio]-1-propanesulfonate (PSBMA) polymer was synthesized to self-assemble into physical hydrogels due to the inter- and intramolecular ion interactions. The strong static interaction bonding density has a substantial impact on the gelation and physicochemical properties, which is beneficial to clinical applications and offers a novel way to obtain the desired hydrogel for a specific biomedical application. Intriguingly, this PSBMA polymer can be customized into a transient network with outstanding antifouling capability depending on the ion concentration. As ion concentration increases, the PSBMA hydrogel dissociated completely, endowing it as a candidate for adhesion prevention. In the cecum-sidewall model, the PSBMA hydrogel demonstrated superior anti-adhesion properties than commercial HA hydrogel. Furthermore, we have demonstrated that this PSBMA hydrogel could inhibit the inflammatory response and encourage anti-fibrosis resulting in adhesion prevention. Most surprisingly, the recovered skins of cecum and sidewall are as smooth as the control skin without any scar and damage. In conclusion, a practical hydrogel was synthesized using a facile method based on purely zwitterionic materials, and this ion-sensitive, antifouling adjustable supramolecular hydrogel with great clinic transform potential is a promising barrier for preventing postoperative tissue adhesion. STATEMENT OF SIGNIFICANCE: The development of hydrogels with satisfactory coverage, long retention time, facile synthetic method, and good biocompatibility is vital for preventing peritoneal adhesions. Herein, we developed a salt sensitive purely zwitterionic physical hydrogel poly 3-[2-(methacryloyloxy)ethyl](dimethyl)-ammonio]-1-propanesulfonate (PSBMA) hydrogel to effectively prevent postoperative and recurrent abdominal adhesions. The hydrogel was simple to synthesize and easy to use. In the cecum-sidewall model, PSBMA hydrogel could instantaneously adhere and fix on irregular surfaces and stay in the wound for more than 10 days. The PSBMA hydrogel could inhibit the inflammatory response, encourage anti-fibrosis, and restore smoothness to damaged surfaces resulting in adhesion prevention. Overall, the PSBMA hydrogel is a promising candidate for the next generation of anti-adhesion materials to meet clinical needs.

Supertough and Highly Stretchable Silk Protein-based Films with Controlled Biodegradability

Naturally derived protein-based biopolymers are considered potential biomaterials in biomedical applications and eco-friendly materials for replacing current petroleum-based polymers due to their good biocompatibility, low environmental impact, and tunable degradability. However, current strategies for fabricating protein-based materials with superior properties and tailored functionality in a scalable manner are still lacking. Here, we demonstrate an aqueous-based scalable approach for fabricating silk protein-based films through controlled molecular self-assembly (CMS) of silk proteins with plasticizers and salt ions. The films fabricated using this method can achieve a toughness of up to 64±5 MJ/m³ with a stretchability of up to 574±31%. We also demonstrate the tunable enzymatic degradability, low in vitro cytotoxicity, and good in vivo biocompatibility of the films. Furthermore, the films can be patterned with predesigned complex structures through laser cutting and functionalized with bioactive components. The functional silk protein-based films show great potential in various applications, including flexible electronics, bioelectronics, tissue engineering, and bioplastic packaging. STATEMENT OF SIGNIFICANCE: Inspired by the naturally optimized multi-scale self-assembly of silk proteins in natural silks, we develop an aqueous-based approach for scalable production of superior protein-based films through controlled molecular self-assembly (CMS) of silk proteins with glycerol and calcium ions. The prepared silk films present outstanding mechanical properties, controlled enzymatic biodegradability, low in vitro cytotoxicity, and good in vivo biocompatibility. Notably, the films fabricated using this method can achieve a high toughness of 64±5 MJ/m³ with a stretchability of 594±31%. The approach introduced in this work provides a facile route toward making silk-based materials with superior properties. It also paves new avenues for developing functional protein-based materials with precisely controlled structures and properties for various applications.

N, O-carboxymethyl chitosan/oxidized cellulose composite sponge containing ε-poly-l-lysine as a potential wound dressing for the prevention and treatment of postoperative adhesion

Herein, we designed and fabricated a biodegradable composite sponge which main component contained N, O-carboxymethyl chitosan (N,O-CS) and oxidized cellulose nanocrystals (TOCN) as a potential wound dressing for the prevention and treatment of postoperative adhesion. In order to improve antimicrobial properties of N,O-CS/TOCN composite sponges, natural antimicrobial agents (ε-Poly-l-Lysine，EPL) were successfully introduced and the EPL/N,O-CS/TOCN composite sponge exhibited excellent antibacterial properties and biological security. The EPL/N,O-CS/TOCN composite sponge can be degraded in vivo within 3 weeks. Finally, we analyzed the anti-adhesion performance of EPL/N,O-CS/TOCN composite sponge through a rat model of sidewall defect-cecum abrasion. These results demonstrated that EPL/N,O-CS/TOCN-treated group can effectively reduce the peritoneal adhesion formation than the commercial soluble gauze group and normal saline group, which mainly attribute to the excellent hemostatic function and tissue repair function of EPL/N,O-CS/TOCN composite sponge. It is believed that the EPL/N,O-CS/TOCN composite sponge will prove to be as a new medical device treat the internal tissue/organ repair and simultaneous prevention of postoperative adhesion.

An Injectable Peptide Hydrogel Constructed of Natural Antimicrobial Peptide J-1 and ADP Shows Anti-Infection, Hemostasis, and Antiadhesion Efficacy

Postoperative adhesion is a common complication of abdominal surgery, which always has many adverse effects in patients. At present, there is still a lack of effective treatment measures and materials to prevent adhesion in the clinics. Herein, we report the potential use of J-1-ADP hydrogel formed by natural antimicrobial peptide jelleine-1 (J-1) self-assembling in adenosine diphosphate (ADP) sodium solution to prevent postsurgery adhesion formation. J-1-ADP hydrogel was found to have good antimicrobial activity against the bacteria and fungi tested and can be used to prevent tissue infection, which was thought to be one of the incitements of adhesion. Due to ADP being a platelet-activating factor, J-1-ADP hydrogel showed significant hemostatic activity in vitro verified by whole blood coagulation, plasma coagulation, platelet activation, and platelet adhesion assays. Further, it showed potent hemostatic activity in a mouse liver hemorrhage model. Bleeding was believed to be a cause of the formation of postsurgery adhesion. J-1-ADP hydrogel had a significant antiadhesion effect in a rat side wall defect-cecum abrasion model. In addition, it had good biocompatibility and degradation properties. So the present study may provide an alternative strategy for designing antimicrobial peptide hydrogel material to prevent postoperative adhesion formation in the clinic.

Curcumin polymeric membranes for postoperative peritoneal adhesion: Comparison of nanofiber vs. film and phospholipid-enriched vs. non-enriched formulations

Intra-abdominal adhesion remains a major postoperative problem and is able to place individuals at lifelong risk of serious complications. Among available approaches, insertion of a barrier membrane at the site of injury partially inhibited adhesion formation. Moreover, the local administration of an anti-adhesive agent showed some favorable effects. In this study, we aimed to prepare and fully characterize polycaprolactone (PCL)-based film casts and electrospun nanofibers (NFs) containing a natural anti-inflammatory agent, curcumin (CUR), with extended-release properties. We also compared their efficiencies in preventing tissue adhesions. Additionally, the impact of soy phosphatidylcholine (SPC) enrichment on adhesion prevention was investigated. Prepared membranes were evaluated in terms of surface morphology (SEM, AFM), surface wettability, CUR release profiles, structural properties (FTIR, XRD, DSC), and mechanical behaviors. To further analyze the anti-adhesion effectiveness, a cecal abrasion model was performed on rats. SEM and AFM images showed a smoother surface in SPC-containing films. Concerning NFs, uniform bead-free fibers were observed and SPC containing NFs showed higher conductivity and lower viscosity and therefore, smaller fibers. All formulations exhibited sustained drug release over 4 weeks. In vivo findings revealed the superior performance of films compared to NFs and phospholipid-enriched formulations over non-enriched ones. Among all film formulations and in comparison to the positive control (Seprafilm®), CUR-SPC-PCL films significantly reduced peritoneal adhesions, as evidenced by gross examination, histological evaluation and immunohistochemical (IHC) analysis. The remarkable in vivo anti-adhesion activity together with suitable in vitro properties have made CUR-SPC-PCL films a promising system for postoperative anti-adhesion purposes in the clinic.

A functional PVA aerogel-based membrane obtaining sutureability through modified electrospinning technology and achieving promising anti-adhesion effect after cardiac surgery

Pericardial barrier destruction, inflammatory cell infiltration, and fibrous tissue hyperplasia, trigger adhesions after cardiac surgery. There are few anti-adhesion materials that are both functional and sutureable for pericardial reconstruction. Besides, a few studies have reported on the mechanism of preventing pericardial adhesion. Herein, a functional barrier membrane with sutureability was developed via a modified electrospinning method. It was composed of poly(l-lactide-co-caprolactone) (PLCL) nanofibers, poly(vinyl alcohol) (PVA) aerogel, and melatonin, named PPMT. The PPMT had a special microstructure manifested as a staggered arrangement of nanofibers on the surface and a layered macroporous aerogel structure in a cross-section. Besides providing the porosity and hydrophilicity obtained from PVA, the structure also had suitable mechanical properties for stitching due to the addition of PLCL nanofibers. Furthermore, it inhibited the proliferation of fibroblasts by suppressing the activation of Fas and P53, and achieved anti-inflammatory effects by affecting the activity of inflammatory cells and reducing the release of pro-inflammatory factors, such as interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α). Finally, in vivo transplantation showed that it up-regulated the expression of matrix metalloproteinase-1 (MMP1) and tissue inhibitor of metalloproteinase-1 (TIMP1), and down-regulated the expression of Vinculin and transforming growth factor β (TGF-β) in the myocardium, thereby reducing the formation of adhesions. Collectively, these results demonstrate a great potential of PPMT membrane for practical application to anti-adhesion.

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A functional PVA aerogel-based membrane (PPMT) obtained sutureability through modified electrospinning technology.

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The primary mechanism to anti-adhesion of PPMT membrane was explored.

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Promising anti-adhesion effect of PPMT membrane was accomplished in pericardium reconstruction in rabbit.

A phlorotannins-loaded homogeneous acellular matrix film modulates post-implantation inflammatory responses

Peritendinous adhesion mainly occurs between proliferating fibrous tissues and adjacent normal organs after surgery. Many physical barriers are applied to the implanted site to prevent peritendinous adhesion. However, these barriers often trigger inflammatory responses. Therefore, our study sought to develop phlorotannins-loaded cartilage acellular matrix (CAM) films as a physical barrier and investigate their inhibitory effect on inflammatory responses, which are associated with the induction of postoperative peritendinous adhesion (PAA). Our findings indicated that incorporating phlorotannin into the CAM film did not affect its unique characteristics including its thermal and spectroscopic properties. Moreover, the phlorotannins-loaded CAM films suppressed the expression of inflammatory mediators on RAW 264.7 macrophages stimulated using Escherichia coli lipopolysaccharides and exhibited an anti-inflammatory effect when implanted subcutaneously in rats. Therefore, our results highlight the potential of phlorotannins-loaded CAM films as a promising physical barrier to prevent PAA.

Prevention of Post-Operative Adhesions: A Comprehensive Review of Present and Emerging Strategies

Post-operative adhesions affect patients undergoing all types of surgeries. They are associated with serious complications, including higher risk of morbidity and mortality. Given increased hospitalization, longer operative times, and longer length of hospital stay, post-surgical adhesions also pose a great financial burden. Although our knowledge of some of the underlying mechanisms driving adhesion formation has significantly improved over the past two decades, literature has yet to fully explain the pathogenesis and etiology of post-surgical adhesions. As a result, finding an ideal preventative strategy and leveraging appropriate tissue engineering strategies has proven to be difficult. Different products have been developed and enjoyed various levels of success along the translational tissue engineering research spectrum, but their clinical translation has been limited. Herein, we comprehensively review the agents and products that have been developed to mitigate post-operative adhesion formation. We also assess emerging strategies that aid in facilitating precision and personalized medicine to improve outcomes for patients and our healthcare system.

Antibacterial, hemostasis, adhesive, self-healing polysaccharides-based composite hydrogel wound dressing for the prevention and treatment of postoperative adhesion

Herein, we fabricated novel self-healing, in situ injectable, biodegradable, and non-toxic hydrogels anti-adhesion barrier materials composed of N, O-carboxymethyl chitosan (N,O-CS) and oxidized dextran (ODA) without requiring any chemical cross-linking agent or external stimuli triggers for the prevention and treatment of post-operative peritoneal adhesions. The N,O-CS/ODA hydrogels have a good suitable gelation time, good cytocompatibility and hemocompatibility, good antibacterial activity, excellent biodegradable and biocompatible, and can effectively inhibit the adhesion of fibroblasts to the wound, thereby suggesting that N,O-CS/ODA hydrogels are suitable for preventing post-operative adhesion. Meanwhile, a rat injury sidewall-cecum abrasion model is developed to investigate the efficacy of these hydrogels in achieving post-operative anti-adhesion. A significant reduction of peritoneal adhesions (10% rat with lower score adhesion) is observed in the N,O-CS/ODA-hydrogel-treated group compared with the commercial hydrogel and control groups. These results demonstrated that N,O-CS/ODA hydrogel could effectively prevent post-operative peritoneal adhesion without side effects. Therefore, the N,O-CS/ODA hydrogels with multi-functional properties exhibit great potential for the prevention and treatment of postoperative adhesion.

An Ultrasoft Self-Fused Supramolecular Polymer Hydrogel for Completely Preventing Postoperative Tissue Adhesion

The intermolecular H-bonding density heavily influences the gelation and rheological behavior of hydrogen-bonded supramolecular polymer hydrogels, thus offering a delicate pathway to tailor their physicochemical properties for meeting a specific biomedical application. Herein, one methylene spacer between two amides in the side chain of N-acryloyl glycinamide (NAGA) is introduced to generate a variant monomer, N-acryloyl alaninamide (NAAA). Polymerization of NAAA in aqueous solution affords an unprecedented ultrasoft and highly swollen supramolecular polymer hydrogel due to weakened H-bonds caused by an extra methylene spacer, which is verified by variable-temperature Fourier transform infrared (FTIR) spectroscopy and simulation calculation. Intriguingly, poly(N-acryloyl alaninamide) (PNAAA) hydrogel can be tuned to form a transient network with a self-fused and excellent antifouling capability that results from the weakened dual amide H-bonding interactions and enhanced water-amide H-bonding interactions. This self-fused PNAAA hydrogel can completely inhibit postoperative abdominal adhesion and recurrent adhesion after adhesiolysis in vivo. This transient hydrogel network allows for its disintegration and excretion from the body. The molecular mechanism studies reveal the signal pathway of PNAAA hydrogel in inhibiting inflammatory response and regulating fibrinolytic system balance. This self-fused, antifouling ultrasoft supramolecular hydrogel is promising as a barrier biomaterial for completely preventing postoperative tissue adhesion.

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

Hyaluronic acid as a bioactive component for bone tissue regeneration: Fabrication, modification, properties, and biological functions

Hyaluronic acid (HA) is widely distributed in the human body, and it is heavily involved in many physiological functions such as tissue hydration, wound repair, and cell migration. In recent years, HA and its derivatives have been widely used as advanced bioactive polymers for bone regeneration. Many medical products containing HA have been developed because this natural polymer has been proven to be nontoxic, noninflammatory, biodegradable, and biocompatible. Moreover, HA-based composite scaffolds have shown good potential for promoting osteogenesis and mineralization. Recently, many HA-based biomaterials have been fabricated for bone regeneration by combining with electrospinning and 3D printing technology. In this review, the polymer structures, processing, properties, and applications in bone tissue engineering are summarized. The challenges and prospects of HA polymers are also discussed.

Dual-functional anti-adhesion barrier prepared using micro-hierarchical structured and neutralized shellac films for drug release

Micro-hierarchical structured shellac films were prepared using a solution casting method with dodecyltrichloro-immobilized shellac microparticles. We evaluated two opposite surfaces of the shellac films-one a micro-hierarchical structured side and the other a neutralized shellac side using alkali ethanol-for their applications in the medical field. A bending strength test using a tensile strength testing machine and measurement of surface hardness using a scratch hardness tester indicated that the optimal composition of the base films comprised 15% shellac and 10% calcium phosphate as durability promoting agents. Further, dodecyltrichloro-immobilized shellac microparticles were synthesized and spray-deposited on the films. The solubility of shellac increased as the pH of the shellac solution increased. Analyses of cell adhesion, proliferation, and anti-thrombus efficiency were performed using a WST assay, field emission scanning electron microscope, and hemocytometer. The contact angle with the micro-hierarchical structure surface was approximately 150°. The spray-deposited shellac film yielded a lower cell and platelet adhesion rate (20%) than the untreated film. These results indicate that the micro-hierarchical structure has unique properties and that this novel superhydrophobic biodegradable shellac film can be applied as a blood/tissue-compatible, biodegradable material for implantable medical devices that need an anti-adhesion barrier.