Clinical Use of the Self-Assembling Peptide RADA16: A Review of Current and Future Trends in Biomedicine

Wound microenvironment-responsive peptide hydrogel with multifunctionalities for accelerating wound healing

The fabrication of wound microenvironment-responsive peptide hydrogels with hemostatic ability, antibacterial activity, and wound healing potential remains a challenge. Herein, we constructed a multifunctional dressing by inducing the self-assembly of a peptide (Pep-1) and water-soluble new methylene blue (NMB) through electrostatic interaction. The self-assembly mechanism was demonstrated using a combination of transmission electron microscopy, circular dichroism spectrum, fluorescence spectrum, Zeta potential, and rheological analysis. The Pep-1/NMB hydrogel also exhibited a faster drug release rate in wound acidic environment. Furthermore, when Pep-1/NMB was exposed to a 635 nm laser, its antibacterial ratios increased sharply to 95.3%, indicating remarkably improved antibacterial effects. The findings from the blood coagulation and hemostasis assay indicated that Pep-1/NMB effectively enhanced the speed of blood clotting in vitro and efficiently controlled hemorrhage in a mouse liver hemorrhage model. Meanwhile, hemolytic and cytotoxicity evaluation revealed that the hydrogel had excellent hemocompatibility and cytocompatibility. Finally, the findings from the wound healing studies and H&E staining indicated that the Pep-1/NMB hydrogel had a significant impact on cell migration and wound repair. The results indicated that wound microenvironment-responsive Pep-1/NMB hydrogel had significant potential as a highly effective wound dressing platform, offering rapid hemostasis, antibacterial, and wound healing acceleration properties.

Recent research advances on polysaccharide-, peptide-, and protein-based hemostatic materials: A review

Hemorrhage is a potentially life-threatening emergency that can occur at any time or place. Whether traumatic, congenital, surgical, disease-related, or drug-induced, bleeding can lead to severe complications or death. Therefore, the development of efficient hemostatic materials is critical. However, the results and prognosis demonstrated by clinical means of hemostasis do not reach expectations. With the development of technology, novel hemostatic materials have been developed from polysaccharides (chitosan, hyaluronic acid, alginate, cellulose, cyclodextrins, starch, dextran, and carrageenan), peptides (self-assembling peptides), and proteins (silk fibroin, collagen, gelatin, keratin, and thrombin). These new materials exhibit high hemostatic efficacy due to the enhancement or interaction of various hemostatic mechanisms. The main forms include adhesives, sealants, bandages, hemostatic powders, and hemostatic sponges. This article introduces the clotting process and principles of hemostatic methods and reviews the research on polysaccharide-, peptide-, and protein-based hemostatic materials in the last five years. The design ideas and hemostatic principles of polysaccharide-, peptide-, and protein-based hemostatic materials are mainly introduced. Finally, we summarize material designs, advantages, disadvantages, and challenges regarding hemostatic materials.

Efficacy and feasibility of the RADA16 self-assembling peptide, PuraStat® for haemostasis in laparoscopic gynaecological surgery: A pilot study

Bleeding after laparoscopic gynaecological surgery remains a potential complication. We assessed RADA16 (PuraStat®), a topical self-assembling peptide haemostatic agent, in a pilot study of 46 women undergoing laparoscopic gynaecological surgery. The primary outcome was intraoperative haemostatic efficacy for resection site bleeding. Haemostasis was achieved in all intraoperative bleeding situations (40/40 participants: 100%) with no clinically significant surgical bed bleeding or complications. Mean volume and time required to achieve haemostasis were 6 mL and 14 sec, respectively. This study suggests that PuraStat® is a safe, effective haemostatic agent in laparoscopic gynaecological surgery. Randomised controlled trials are warranted to confirm these findings.

Experimental Study on Rapid Hemostasis Using Peptide Hydrogels

Uncontrolled hemorrhaging resulting from trauma, surgery, and disease-associated or drug-induced blood disorders can cause significant morbidities and mortalities in civilian and military populations. Self-assembling peptide nanofibers are particularly attractive due to their rapid and efficient hemostasis, biocompatibility, and wound-healing properties. In this study, we designed two types of 12-residue peptides by using a strong fishnet-like peptide sequence and a pro-cell adhesion sequence (Arg-Gly-Asp, RGD). The peptides are HN2-X-Ser-Phe-Cys-Phe-Lys-Phe-Glu-X-Arg-Gly-Asp-OH (where X is Pro or Tyr), which dissolve in deionized (DI) water and form stable and transparent functional hydrogels. Transmission electron microscopy and scanning electron microscopy demonstrated that the two peptides self-assemble into nanowebs and nanofibers, forming a fishnet-like and three-dimensional network structure. Circular dichroism and Fourier transform infrared spectroscopy analysis demonstrated that the self-assembled peptides mainly adopt a β-sheet structure with β-turn and α-helix as auxiliary assembly growth. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and SEM analysis showed that the cell survival rates were very good, delivering an obvious promotion of cell proliferation of fibroblasts and hepatocytes. Importantly, in vivo hemostasis delivered that the self-assembled peptide nanowebs and nanofibers had a good hemostatic effect on rat saphenous vein and liver bleeding, achieving 38 s faster hemostasis, which was better than commercial "Instantaneous" hemostatic powder. Accoupling the fast hemostasis and effective promotion of liver defect rapid repair, the peptide self-assembly strategy offers a clinically promising treatment option for life-threatening liver bleeding and serves as a renewed impetus for the development of peptide hydrogels as effective hemostatic agents.

Supramolecular self-assembled peptide-engineered nanofibers: A propitious proposition for cancer therapy

Cancer is a devastating disease that causes a substantial number of deaths worldwide. Current therapeutic interventions for cancer include chemotherapy, radiation therapy, or surgery. These conventional therapeutic approaches are associated with disadvantages such as multidrug resistance, destruction of healthy tissues, and tissue toxicity. Therefore, there is a paradigm shift in cancer management wherein nanomedicine-based novel therapeutic interventions are being explored to overcome the aforementioned disadvantages. Supramolecular self-assembled peptide nanofibers are emerging drug delivery vehicles that have gained much attention in cancer management owing to their biocompatibility, biodegradability, biomimetic property, stimuli-responsiveness, transformability, and inherent therapeutic property. Supramolecules form well-organized structures via non-covalent linkages, the intricate molecular arrangement helps to improve tissue permeation, pharmacokinetic profile and chemical stability of therapeutic agents while enabling targeted delivery and allowing efficient tumor imaging. In this review, we present fundamental aspects of peptide-based self-assembled nanofiber fabrication their applications in monotherapy/combinatorial chemo- and/or immuno-therapy to overcome multi-drug resistance. The role of self-assembled structures in targeted/stimuli-responsive (pH, enzyme and photo-responsive) drug delivery has been discussed along with the case studies. Further, recent advancements in peptide nanofibers in cancer diagnosis, imaging, gene therapy, and immune therapy along with regulatory obstacles towards clinical translation have been deliberated.

RADA-16-based Self-assembled Peptide Nanofiber Scaffolds Loaded with TGF-β1 Enhance the Chondrogenic Differentiation Potential of BMSCs In vitro

OBJECTIVE

At present, cartilage repair does not offer ideal efficacy. Fortunately, recent studies have claimed that RADA-16 peptide is an attractive therapeutic strategy for repairing cartilage defects. Therefore, this study tried to explore the effect of RADA-16 loaded with transforming growth factor-beta (TGF-β) 1 on cartilage differentiation of bone marrow mesenchymal stem cells (BMSCs).

METHODS

First, the RADA-16 peptide was synthesized by solid phase peptide, and a well-defined hydrogel was formed by supramolecular peptide self-assembly. Then, TGF-β1 (loading concentration of 10 ng/mL) was loaded into RADA-16, with scanning electron microscopy to observe the morphology of the TGF-β1/RADA-16 hydrogel and detect its related properties. Next, BMSCs were isolated from bone marrow samples and identified. TGF-β1/RADA-16 was co-cultured with L929, BMSCs, and C28/I2 cells, respectively, and the survival and proliferation ability of the cells was determined by live/dead cell staining and MTT assay. Chondrogenic differentiation and sGAG production of BMSCs were determined by Alcian blue staining and Blyscan assay, the expression of cartilage-associated genes by qRT-PCR, and the levels of inflammatory factors by ELISA. As for mechanism investigation, the Smad and ERK/MAPK signaling pathways were detected by western blot.

RESULTS

RADA-16 hydrogel exhibited a well-distributed and interconnected porous surface structure, with a loading rate of 91.9% for TGF-β1. The TGF-β1/RADA-16 hydrogel had good release and degradation properties, and had no negative effect on the survival and proliferation ability of BMSCs, L929, and C28/I2 cells. Importantly, TGF-β1/RADA-16 hydrogel significantly accelerated chondrogenic differentiation and sGAG generation in BMSCs, and decreased pro-inflammatory factor production. In addition, the hydrogel also significantly activated the Smad and ERK/MAPK pathways of BMSCs.

CONCLUSION

RADA-16 loaded with TGF-β1 has good biological properties and can enhance the chondrogenic differentiation ability of BMSCs.

Injectable Multifunctional Composite Hydrogel as a Combination Therapy for Preventing Postsurgical Adhesion

Postsurgical adhesion (PA) is a common and serious postoperative complication that affects millions of patients worldwide. However, current commercial barrier materials are insufficient to inhibit diverse pathological factors during PA formation, and thus, highly bioactive materials are needed. Here, this work designs an injectable multifunctional composite hydrogel that can serve as a combination therapy for preventing PA. In brief, this work reveals that multiple pathological events, such as chronic inflammatory and fibrotic processes, contribute to adhesion formation in vivo, and such processes can not be attenuated by barrier material (e.g., hydrogel) alone treatments. To solve this limitation, this work designs a composite hydrogel made of the cationic self-assembling peptide KLD2R and TGF-β receptor inhibitor (TGF-βRi)-loaded mesenchymal stem cell-derived nanovesicles (MSC-NVs). The resulting composite hydrogel displays multiple functions, including physical separation of the injured tissue areas, antibacterial effects, and local delivery and sustained release of anti-inflammatory MSC-NVs and antifibrotic TGF-βRi. As a result, this composite hydrogel effectively inhibited local inflammation, fibrosis and adhesion formation in vivo. Moreover, the hydrogel also exhibits good biocompatibility and biodegradability in vivo. Together, the results highlight that this "all-in-one" composite hydrogel strategy may provide insights into designing advanced therapies for many types of tissue injury.

A transparent synthetic peptide hydrogel as a haemostatic agent in athermal nerve sparing robot-assisted radical prostatectomy: an observational study

Background

PuraStat® is a new synthetic haemostatic agent constituting peptides that self-assemble into sheets when exposed to ionic charges. The objective of this submission is to assess the perioperative, functional and user-reported outcomes of PuraStat® as an athermal topical haemostatic agent for use on the neurovascular bundle (NVB) in robot-assisted radical prostatectomy (RARP), and to inform further research into this developing field.

Methods

Demographic and disease data for 29 consecutive patients undergoing RARP were recorded. PuraStat® was used as the primary haemostatic agent to the NVB, without thermal or suture haemostasis, unless necessary. Preoperative, 1-h postoperative and 24-h postoperative haemoglobin (Hb) were measured. Operative data including postoperative complications up to 30 days were noted. Urinary function, continence and erectile function (EF) were measured pre- and postoperatively with the International Prostate Symptom Score (IPSS), patient reporting of pad usage, and International Index of Erectile Function (IIEF)-5 respectively. A qualitative assessment of PuraStat® was made intraoperatively by the surgical assistant in the following categories: transparency, haemostatic efficacy, ready-to-use, handling, and overall satisfaction.

Results

Twenty-nine males aged between 49 and 75 years underwent a nerve-sparing RARP under a single surgeon for clinically significant prostate cancer with PuraStat® used as the primary haemostatic agent at the NVB. One patient required an additional haemostatic suture. The median prostate volume was 36 mL. Mean blood loss was 363 mL. The mean Hb at 1 and 24 h postoperative was 135.2 and 125.1 mg/dL. Median Hb change from 1-24 h postoperative was 11 mg/dL. No transfusions were required, and there were no postoperative complications. Urinary function and continence were preserved. EF in our series was lower than published data.

Conclusions

Our observational study suggests that PuraStat® is a safe haemostatic agent in RARP with similar perioperative bleeding outcomes, comparable long-term urinary outcomes and a high level of intraoperative user satisfaction. The effects on EF requires further investigation. PuraStat® appears to be a useful therapeutic tool for the urologist performing RARPs.

Hybrid Endometrial-Derived Hydrogels: Human Organoid Culture Models and In Vivo Perspectives

The endometrium plays a vital role in fertility, providing a receptive environment for embryo implantation and development. Understanding the endometrial physiology is essential for developing new strategies to improve reproductive healthcare. Human endometrial organoids (hEOs) are emerging as powerful models for translational research and personalized medicine. However, most hEOs are cultured in a 3D microenvironment that significantly differs from the human endometrium, limiting their applicability in bioengineering. This study presents a hybrid endometrial-derived hydrogel that combines the rigidity of PuraMatrix (PM) with the natural scaffold components and interactions of a porcine decellularized endometrial extracellular matrix (EndoECM) hydrogel. This hydrogel provides outstanding support for hEO culture, enhances hEO differentiation efficiency due to its biochemical similarity with the native tissue, exhibits superior in vivo stability, and demonstrates xenogeneic biocompatibility in mice over a 2-week period. Taken together, these attributes position this hybrid endometrial-derived hydrogel as a promising biomaterial for regenerative treatments in reproductive medicine.

Self-assembling peptide RADA16: a promising scaffold for tissue engineering and regenerative medicine

RADA16 is a peptide-based biomaterial whose acidic aqueous solution spontaneously forms an extracellular matrix-like 3D structure within seconds upon contact with physiological pH body fluids. Meanwhile, its good biocompatibility, low immunogenicity, nontoxic degradation products and ease of modification make it an ideal scaffold for tissue engineering. RADA16 is a good delivery vehicle for cells, drugs and factors. Its shear thinning and thixotropic properties allow it to fill tissue voids by injection and not to swell. However, the weaker mechanical properties and poor hydrophilicity are troubling limitations of RADA16. To compensate for this limitation, various functional groups and polymers have been designed to modify RADA16, thus contributing to its scope and progress in the field of tissue engineering.

Modern Approaches in Wounds Management

Wound management represents a well-known continuous challenge and concern of the global healthcare systems worldwide. The challenge is on the one hand related to the accurate diagnosis, and on the other hand to establishing an effective treatment plan and choosing appropriate wound care products in order to maximize the healing outcome and minimize the financial cost. The market of wound dressings is a dynamic field which grows and evolves continuously as a result of extensive research on developing versatile formulations with innovative properties. Hydrogels are one of the most attractive wound care products which, in many aspects, are considered ideal for wound treatment and are widely exploited for extension of their advantages in healing process. Smart hydrogels (SHs) offer the opportunities of the modulation physico-chemical properties of hydrogels in response to external stimuli (light, pressure, pH variations, magnetic/electric field, etc.) in order to achieve innovative behavior of their three-dimensional matrix (gel-sol transitions, self-healing and self-adapting abilities, controlled release of drugs). The SHs response to different triggers depends on their composition, cross-linking method, and manufacturing process approach. Both native or functionalized natural and synthetic polymers may be used to develop stimuli-responsive matrices, while the mandatory characteristics of hydrogels (biocompatibility, water permeability, bioadhesion) are preserved. In this review, we briefly present the physiopathology and healing mechanisms of chronic wounds, as well as current therapeutic approaches. The rational of using traditional hydrogels and SHs in wound healing, as well as the current research directions for developing SHs with innovative features, are addressed and discussed along with their limitations and perspectives in industrial-scale manufacturing.

Short Peptide Nanofiber Biomaterials Ameliorate Local Hemostatic Capacity of Surgical Materials and Intraoperative Hemostatic Applications in Clinics

Short designer self-assembling peptide (dSAP) biomaterials are a new addition to the hemostat group. It may provide a diverse and robust toolbox for surgeons to integrate wound microenvironment with much safer and stronger hemostatic capacity than conventional materials and hemostatic agents. Especially in noncompressible torso hemorrhage (NCTH), diffuse mucosal surface bleeding, and internal medical bleeding (IMB), with respect to the optimal hemostatic formulation, dSAP biomaterials are the ingenious nanofiber alternatives to make bioactive neural scaffold, nasal packing, large mucosal surface coverage in gastrointestinal surgery (esophagus, gastric lesion, duodenum, and lower digestive tract), epicardiac cell-delivery carrier, transparent matrix barrier, and so on. Herein, in multiple surgical specialties, dSAP-biomaterial-based nano-hemostats achieve safe, effective, and immediate hemostasis, facile wound healing, and potentially reduce the risks in delayed bleeding, rebleeding, post-operative bleeding, or related complications. The biosafety in vivo, bleeding indications, tissue-sealing quality, surgical feasibility, and local usability are addressed comprehensively and sequentially and pursued to develop useful surgical techniques with better hemostatic performance. Here, the state of the art and all-round advancements of nano-hemostatic approaches in surgery are provided. Relevant critical insights will inspire exciting investigations on peptide nanotechnology, next-generation biomaterials, and better promising prospects in clinics.

Engineering a Two-Component Hemostat for the Treatment of Internal Bleeding through Wound-Targeted Crosslinking

Primary hemostasis (platelet plug formation) and secondary hemostasis (fibrin clot formation) are intertwined processes that occur upon vascular injury. Researchers have sought to target wounds by leveraging cues specific to these processes, such as using peptides that bind activated platelets or fibrin. While these materials have shown success in various injury models, they are commonly designed for the purpose of treating solely primary or secondary hemostasis. In this work, a two-component system consisting of a targeting component (azide/GRGDS PEG-PLGA nanoparticles) and a crosslinking component (multifunctional DBCO) is developed to treat internal bleeding. The system leverages increased injury accumulation to achieve crosslinking above a critical concentration, addressing both primary and secondary hemostasis by amplifying platelet recruitment and mitigating plasminolysis for greater clot stability. Nanoparticle aggregation is measured to validate concentration-dependent crosslinking, while a 1:3 azide/GRGDS ratio is found to increase platelet recruitment, decrease clot degradation in hemodiluted environments, and decrease complement activation. Finally, this approach significantly increases survival relative to the particle-only control in a liver resection model. In light of prior successes with the particle-only system, these results emphasize the potential of this technology in aiding hemostasis and the importance of a holistic approach in engineering new treatments for hemorrhage.

Stimulus-responsive peptide hydrogels: a safe and least invasive administration approach for tumor treatment

Tumours, with increasing mortality around the world, have bothered human beings for decades. Enhancing the targeting of antitumor drugs to tumour tissues is the key to enhancing their antitumor effects. The tumour microenvironment is characterised by a relatively low pH, overexpression of certain enzymes, redox imbalance, etc. Therefore, smart drug delivery systems that respond to the tumour microenvironment have been proposed to selectively release antitumor drugs. Among them, peptide hydrogels as a local drug delivery system have received much attention due to advantages such as high biocompatibility, degradability and high water-absorbing capacity. The combination of peptide segments with different physiological functions allows for tumour targeting, self-aggregation, responsiveness, etc. Morphological and microstructural changes in peptide hydrogels can occur when utilising the inherent pathological microenvironment of tumours to trigger drug release, which endows such systems with limited adverse effects and improved therapeutic efficiency. Herein, this review outlined the driving forces, impact factors, and sequence design in peptide hydrogels. We also discussed the triggers to induce the transformation of peptide-based hydrogels in the tumour microenvironment and described the advancements of peptide-based hydrogels for local drug delivery in tumour treatment. Finally, we gave a brief perspective on the prospects and challenges in this field.

Self-assembling RADA16 peptide hydrogel supports hemostasis, synechiae reduction, and wound healing in a sheep model of endoscopic nasal surgery

OBJECTIVES

Complications of endoscopic sinus/nasal turbinate surgery include postoperative hemorrhage, synechiae formation, and poor wound healing. Our primary objectives were to evaluate whether a topical hydrogel based on self-assembling RADA16 peptides: i) reduces bleeding and synechiae formation, and ii) supports wound healing, using a sheep nasal surgery model.

METHODS

Thirty sheep received endoscopic surgery-created bilateral nasal mucosal injuries on the middle turbinate/opposing septum. Injuries were randomly assigned RADA16, Gelatin-thrombin, or no treatment. Outcomes included intra-operative hemostasis, scar tissue/synechiae formation and wound healing at 2 weeks and the 6-week study terminus, and histopathology.

RESULTS

Intra-operative hemostasis time improved with RADA16 and Gelatin-thrombin versus Control wounds (139.7±56.2 s, 145.4±58.1 s, and 224.0±69.9 s, respectively; p < 0.0001 for both comparisons). Two-week synechiae scores (maximum 4 points) were similar in Controls (2.9±1.8 points) and Gelatin-thrombin (3.1±1.6 points) wounds (p > 0.05), but were reduced in RADA16 sites by 91% versus Controls and 92% versus Gelatin-thrombin treatment (0.3±0.6 points; p < 0.0001 for both comparisons). Six-week synechiae scores were similar in Control (1.1±1.7 points) and Gelatin-thrombin (1.7±2.0 points) wounds (p > 0.05), but reduced 100% in RADA16-treated wounds. Synechiae occurred in fewer RADA16-treated sites at 2 weeks (20%) versus Gelatin-thrombin (80%) and Controls (75%; p < 0.01) and at 6 weeks (0%, 50% and 35%, respectively; p < 0.01). RADA16 was associated with significantly lower 6-week histopathology scores, driven by reduced submucosal fibrosis and angiogenesis.

CONCLUSION

Although RADA16 and Gelatin-thrombin similarly accelerated hemostasis in this sheep endoscopic sinus surgery model, only RADA16 reduced postoperative synechiae formation at 2 weeks with an absence of synechiae at 6 weeks. Histology suggested RADA16 enhanced mucosal regeneration.

Self-Assembling Peptide RADA16 Nanofiber Scaffold Hydrogel-Wrapped Concentrated Growth Factors in Osteogenesis of MC3T3

Concentrated growth factors (CGFs) are widely used in surgery with bone grafting, but the release of growth factors from CGFs is rapid. RADA16, a self-assembling peptide, can form a scaffold that is similar to the extracellular matrix. Based on the properties of RADA16 and CGF, we hypothesized that the RADA16 nanofiber scaffold hydrogel could enhance the function of CGFs and that the RADA16 nanofiber scaffold hydrogel-wrapped CGFs (RADA16-CGFs) would perform a good osteoinductive function. This study aimed to investigate the osteoinductive function of RADA16-CGFs. Scanning electron microscopy, rheometry, and ELISA were performed, and MC3T3-E1 cells were used to test cell adhesion, cytotoxicity, and mineralization after administration with RADA16-CGFs. We found that RADA16 endowed with the sustained release of growth factors from CGFs, which can help maximize the function of CGFs in osteoinduction. The application of the atoxic RADA16 nanofiber scaffold hydrogel with CGFs can be a new therapeutic strategy for the treatment of alveolar bone loss and other problems that require bone regeneration.

Efficacy of self-assembling peptide in mitigating delayed bleeding after advanced endoscopic resection of gastrointestinal lesions: A meta-analysis

Background and study aims  Advanced endoscopic resection techniques carry a risk of delayed bleeding (DB). A novel fully synthetic self-assembling peptide (SAP) has shown promising results in mitigating this risk. In this meta-analysis, we evaluated all available data and analyzed the effectiveness of SAP in reducing DB after advanced endoscopic resection of gastrointestinal luminal lesions. Patients and methods  Electronic databases (PubMed, Embase, and Cochrane Library) from January 2010 through October 2022 were searched for publications addressing the use of SAP solution in patients undergoing advanced endoscopic resection of gastrointestinal lesions. Pooled proportions were calculated using fixed (inverse variance) and random-effects (DerSimonian-Laird) models. Results  The initial search identified 277 studies, of which 63 relevant articles were reviewed. The final analysis included data from six studies comprising 307 patients that met inclusion criteria. The pooled rate of DB was 5.73 % (95 % confidence interval [CI] = 3.42-8.59). Mean patient age was 69.40 years ± 1.82. The weighted mean size of resected lesions was 36.20 mm (95 % CI = 33.37-39.02). Endoscopic submucosal dissection was used in 72.69 % (95 % CI = 67.62-77.48), while endoscopic mucosal resection was used in 26.42 % (95 % CI = 21.69-31.44) of the procedures. Among the 307 patients, 36 % were on antithrombotic medications. No adverse events (AEs) were attributable to using SAP, with a pooled rate of 0.00 % (95 % CI = 0.00-1.49). Conclusions  SAP solution appears promising in reducing post-procedural DB after advanced endoscopic resection of high-risk gastrointestinal lesions with no reported AEs.

Synthetic extracellular matrices with function-encoding peptides

The communication of cells with their surroundings is mostly encoded in the epitopes of structural and signalling proteins present in the extracellular matrix (ECM). These peptide epitopes can be incorporated in biomaterials to serve as function-encoding molecules to modulate cell-cell and cell-ECM interactions. In this Review, we discuss natural and synthetic peptide epitopes as molecular tools to bioengineer bioactive hydrogel materials. We present a library of functional peptide sequences that selectively communicate with cells and the ECM to coordinate biological processes, including epitopes that directly signal to cells, that bind ECM components that subsequently signal to cells, and that regulate ECM turnover. We highlight how these epitopes can be incorporated in different biomaterials as individual or multiple signals, working synergistically or additively. This molecular toolbox can be applied in the design of biomaterials aimed at regulating or controlling cellular and tissue function, repair and regeneration.

Molecularly Stimuli-Responsive Self-Assembled Peptide Nanoparticles for Targeted Imaging and Therapy

Self-assembly has emerged as an extensively used method for constructing biomaterials with sizes ranging from nanometers to micrometers. Peptides have been extensively investigated for self-assembly. They are widely applied owing to their desirable biocompatibility, biodegradability, and tunable architecture. The development of peptide-based nanoparticles often requires complex synthetic processes involving chemical modification and supramolecular self-assembly. Stimuli-responsive peptide nanoparticles, also termed "smart" nanoparticles, capable of conformational and chemical changes in response to stimuli, have emerged as a class of promising materials. These smart nanoparticles find a diverse range of biomedical applications, including drug delivery, diagnostics, and biosensors. Stimuli-responsive systems include external stimuli (such as light, temperature, ultrasound, and magnetic fields) and internal stimuli (such as pH, redox environment, salt concentration, and biomarkers), facilitating the generation of a library of self-assembled biomaterials for biomedical imaging and therapy. Thus, in this review, we mainly focus on peptide-based nanoparticles built by self-assembly strategy and systematically discuss their mechanisms in response to various stimuli. Furthermore, we summarize the diverse range of biomedical applications of peptide-based nanomaterials, including diagnosis and therapy, to demonstrate their potential for medical translation.

Release systems based on self-assembling RADA16-I hydrogels with a signal sequence which improves wound healing processes

Self-assembling peptides can be used for the regeneration of severely damaged skin. They can act as scaffolds for skin cells and as a reservoir of active compounds, to accelerate scarless wound healing. To overcome repeated administration of peptides which accelerate healing, we report development of three new peptide biomaterials based on the RADA16-I hydrogel functionalized with a sequence (AAPV) cleaved by human neutrophil elastase and short biologically active peptide motifs, namely GHK, KGHK and RDKVYR. The peptide hybrids were investigated for their structural aspects using circular dichroism, thioflavin T assay, transmission electron microscopy, and atomic force microscopy, as well as their rheological properties and stability in different fluids such as water or plasma, and their susceptibility to digestion by enzymes present in the wound environment. In addition, the morphology of the RADA-peptide hydrogels was examined with a unique technique called scanning electron cryomicroscopy. These experiments enabled us to verify if the designed peptides increased the bioactivity of the gel without disturbing its gelling processes. We demonstrate that the physicochemical properties of the designed hybrids were similar to those of the original RADA16-I. The materials behaved as expected, leaving the active motif free when treated with elastase. XTT and LDH tests on fibroblasts and keratinocytes were performed to assess the cytotoxicity of the RADA16-I hybrids, while the viability of cells treated with RADA16-I hybrids was evaluated in a model of human dermal fibroblasts. The hybrid peptides revealed no cytotoxicity; the cells grew and proliferated better than after treatment with RADA16-I alone. Improved wound healing following topical delivery of RADA-GHK and RADA-KGHK was demonstrated using a model of dorsal skin injury in mice and histological analyses. The presented results indicate further research is warranted into the engineered peptides as scaffolds for wound healing and tissue engineering.

Advances in Hydrogel Adhesives for Gastrointestinal Wound Closure and Repair

Millions of individuals undergo gastrointestinal (GI) tract surgeries each year with common postoperative complications including bleeding, perforation, anastomotic leakage, and infection. Today, techniques such as suturing and stapling seal internal wounds, and electrocoagulation stops bleeding. These methods induce secondary damage to the tissue and can be technically difficult to perform depending on the wound site location. To overcome these challenges and to further advance wound closure, hydrogel adhesives are being investigated to specifically target GI tract wounds because of their atraumatic nature, fluid-tight sealing capability, favorable wound healing properties, and facile application. However, challenges remain that limit their use, such as weak underwater adhesive strength, slow gelation, and/or acidic degradation. In this review, we summarize recent advances in hydrogel adhesives to treat various GI tract wounds, with a focus on novel material designs and compositions to combat the environment-specific challenges of GI injury. We conclude with a discussion of potential opportunities from both research and clinical perspectives.

Bone marrow-derived dedifferentiated fat cells exhibit similar phenotype as bone marrow mesenchymal stem cells with high osteogenic differentiation and bone regeneration ability

BACKGROUND

Mesenchymal stem cells (MSCs) are known to have different differentiation potential depending on the tissue of origin. Dedifferentiated fat cells (DFATs) are MSC-like multipotent cells that can be prepared from mature adipocytes by ceiling culture method. It is still unknown whether DFATs derived from adipocytes in different tissue showed different phenotype and functional properties. In the present study, we prepared bone marrow (BM)-derived DFATs (BM-DFATs), BM-MSCs, subcutaneous (SC) adipose tissue-derived DFATs (SC-DFATs), and adipose tissue-derived stem cells (ASCs) from donor-matched tissue samples. Then, we compared their phenotypes and multilineage differentiation potential in vitro. We also evaluated in vivo bone regeneration ability of these cells using a mouse femoral fracture model.

METHODS

BM-DFATs, SC-DFATs, BM-MSCs, and ASCs were prepared from tissue samples of knee osteoarthritis patients who received total knee arthroplasty. Cell surface antigens, gene expression profile, and in vitro differentiation capacity of these cells were determined. In vivo bone regenerative ability of these cells was evaluated by micro-computed tomography imaging at 28 days after local injection of the cells with peptide hydrogel (PHG) in the femoral fracture model in severe combined immunodeficiency mice.

RESULTS

BM-DFATs were successfully generated at similar efficiency as SC-DFATs. Cell surface antigen and gene expression profiles of BM-DFATs were similar to those of BM-MSCs, whereas these profiles of SC-DFATs were similar to those of ASCs. In vitro differentiation analysis revealed that BM-DFATs and BM-MSCs had higher differentiation tendency toward osteoblasts and lower differentiation tendency toward adipocytes compared to SC-DFATs and ASCs. Transplantation of BM-DFATs and BM-MSCs with PHG enhanced bone mineral density at the injection sites compared to PHG alone in the mouse femoral fracture model.

CONCLUSIONS

We showed that phenotypic characteristics of BM-DFATs were similar to those of BM-MSCs. BM-DFATs exhibited higher osteogenic differentiation potential and bone regenerative ability compared to SC-DFATs and ASCs. These results suggest that BM-DFATs may be suitable sources of cell-based therapies for patients with nonunion bone fracture.

Designed peptide amphiphiles as scaffolds for tissue engineering

Peptide amphiphiles (PAs) are peptide-based molecules that contain a peptide sequence as a head group covalently conjugated to a hydrophobic segment, such as lipid tails. They can self-assemble into well-ordered supramolecular nanostructures such as micelles, vesicles, twisted ribbons and nanofibers. In addition, the diversity of natural amino acids gives the possibility to produce PAs with different sequences. These properties along with their biocompatibility, biodegradability and a high resemblance to native extracellular matrix (ECM) have resulted in PAs being considered as ideal scaffold materials for tissue engineering (TE) applications. This review introduces the 20 natural canonical amino acids as building blocks followed by highlighting the three categories of PAs: amphiphilic peptides, lipidated peptide amphiphiles and supramolecular peptide amphiphile conjugates, as well as their design rules that dictate the peptide self-assembly process. Furthermore, 3D bio-fabrication strategies of PAs hydrogels are discussed and the recent advances of PA-based scaffolds in TE with the emphasis on bone, cartilage and neural tissue regeneration both in vitro and in vivo are considered. Finally, future prospects and challenges are discussed.

Self-assembling peptides as immunomodulatory biomaterials

Self-assembling peptides are a type of biomaterial rapidly emerging in the fields of biomedicine and material sciences due to their promise in biocompatibility and effectiveness at controlled release. These self-assembling peptides can form diverse nanostructures in response to molecular interactions, making them versatile materials. Once assembled, the peptides can mimic biological functions and provide a combinatorial delivery of therapeutics such as cytokines and drugs. These self-assembling peptides are showing success in biomedical settings yet face unique challenges that must be addressed to be widely applied in the clinic. Herein, we describe self-assembling peptides' characteristics and current applications in immunomodulatory therapeutics.

Modification Strategies for Ionic Complementary Self-Assembling Peptides: Taking RADA16-I as an Example

Ion-complementary self-assembling peptides have been studied in many fields for their distinct advantages, mainly due to their self-assembly properties. However, their shortcomings, such as insufficient specific activity and poor mechanical properties, also limited their application. For the better and wider application of these promising biomaterials, ion-complementary self-assembling peptides can be modified with their self-assembly properties not being destroyed to the greatest extent. The modification strategies were reviewed by taking RADA16-I as an example. For insufficient specific activity, RADA16-I can be structurally modified with active motifs derived from the active domain of the extracellular matrix or other related active factors. For weak mechanical properties, materials with strong mechanical properties or that can undergo chemical crosslinking were used to mix with RADA16-I to enhance the mechanical properties of RADA16-I. To improve the performance of RADA16-I as drug carriers, appropriate adjustment of the RADA16-I sequence and/or modification of the RADA16-I-related delivery system with polymer materials or specific molecules can be considered to achieve sustained and controlled release of specific drugs or active factors. The modification strategies reviewed in this paper may provide some references for further basic research and clinical application of ion-complementary self-assembling peptides and their derivatives.

Bulking agents in gastrointestinal endoscopy: present applications and future advances

PURPOSE OF REVIEW

Bulking agents are inert materials injected into an organ to affect the physical properties of the organ for a therapeutic purpose. Various agents have been developed to aid in the treatment of diseases like gastroesophageal reflux disease (GERD), fecal incontinence, obesity, malignancy, hemostasis, and tissue dissection. Here, we review the state of the art in bulking agents in gastrointestinal endoscopy, past failures, current limitations, and where we see the field heading in the future.

RECENT FINDINGS

Though bulking agents have been trialed for various different gastrointestinal diseases, there are currently limited uses in gastrointestinal endoscopy. Though various agents have been trialed for GERD, numerous complications and adverse events have limited its current use. However, for the treatment of fecal incontinence endoscopic bulking agent therapy is a reasonable option. Though in early stages of exploration, bulking agent therapy for enteric protection from radiotherapy may be a promising tool to improve treatment of pancreatic cancer. Bulking agents for tissue dissection have substantially improved lifting agents and complex polyp removal. Bulking agent therapy has not really been explored for endoscopic bariatric therapy or hemostasis but may be a fruitful area for exploration in the future.

SUMMARY

Bulking agent therapy has been trialed for various gastrointestinal diseases with mixed success. There is currently a therapeutic roll in the endoscopic management of fecal incontinence and tissue dissection. A future role in the treatment of GERD, obesity, malignancy, and hemostasis seem feasible.

Fmoc-Diphenylalanine Hydrogels: Optimization of Preparation Methods and Structural Insights

Hydrogels (HGs) are tri-dimensional materials with a non-Newtonian flow behaviour formed by networks able to encapsulate high amounts of water or other biological fluids. They can be prepared using both synthetic or natural polymers and their mechanical and functional properties may change according to the preparation method, the solvent, the pH, and to others experimental parameters. Recently, many short and ultra-short peptides have been investigated as building blocks for the formulation of biocompatible hydrogels suitable for different biomedical applications. Due to its simplicity and capability to gel in physiological conditions, Fmoc-FF dipeptide is one of the most studied peptide hydrogelators. Although its identification dates to 15 ago, its behaviour is currently studied because of the observation that the final material obtained is deeply dependent on the preparation method. To collect information about their formulation, here are reported some different strategies adopted until now for the Fmoc-FF HG preparation, noting the changes in the structural arrangement and behaviour in terms of stiffness, matrix porosity, and stability induced by the different formulation strategy on the final material.

Preventing Postendoscopic Mucosal Resection Bleeding of Large Nonpedunculated Colorectal Lesions

The most common major adverse event of endoscopic mucosal resection (EMR) is clinically significant post-EMR bleeding (CSPEB), with an incidence of 6%-7% in large lesions. Repeat colonoscopy, blood transfusions, or other interventions are often needed. The associated direct costs are much higher than those of an uncomplicated EMR. In this review, we discuss the aspects related to CSPEB of large nonpedunculated polyps, such as risk factors, predictive models, and prophylactic measures, and we highlight evidence for preventive treatment options and explore new methods for bleeding prophylaxis. We also provide recommendations for steps that can be taken before, during, and after EMR to minimize bleeding risk. Finally, this review proposes future directions to reduce CSPEB incidence.

Harnessing the Structural and Functional Diversity of Protein Filaments as Biomaterial Scaffolds

The natural ability of many proteins to polymerize into highly structured filaments has been harnessed as scaffolds to align functional molecules in a diverse range of biomaterials. Protein-engineering methodologies also enable the structural and physical properties of filaments to be tailored for specific biomaterial applications through genetic engineering or filaments built from the ground up using advances in the computational prediction of protein folding and assembly. Using these approaches, protein filament-based biomaterials have been engineered to accelerate enzymatic catalysis, provide routes for the biomineralization of inorganic materials, facilitate energy production and transfer, and provide support for mammalian cells for tissue engineering. In this review, we describe how the unique structural and functional diversity in natural and computationally designed protein filaments can be harnessed in biomaterials. In addition, we detail applications of these protein assemblies as material scaffolds with a particular emphasis on applications that exploit unique properties of specific filaments. Through the diversity of protein filaments, the biomaterial engineer's toolbox contains many modular protein filaments that will likely be incorporated as the main structural component of future biomaterials.

Biomimetic Hydrogel Scaffolds with Copper Peptide-Functionalized RADA16 Nanofiber Improve Wound Healing in Diabetes

Wound healing in diabetes is retarded by the dysfunctional local microenvironment. Although there are many studies using hydrogels as substitutes for natural extracellular matrices (ECMs), hydrogels that can mimic both the structure and functions of natural ECM remain a challenge. Self-assembling peptide RADA16 nanofiber has distinct advantageous to provide a biomimetic extracellular matrix nanofiber structure. However, it is still lack of biological cues to promote angiogenesis that is of vital significance for diabetic wounds healing. With a customized copper peptide GHK functionalized RADA16, an integrated approach using functionalized RADA16 nanofiber to chelate copper ion, has been innovatively proposed in this present study. The acquired composite hydrogel held the biomimetic nanofiber architecture, and exhibited promoting angiogenesis by both enhancing adhesion and proliferation of endothelial cells (EC) in vitro and neovascularization in vivo. It showed that the functionalized nanofiber scaffolds significantly accelerated wound closure, collagen deposition, and tissue remodeling both in healthy and diabetic mice. Furthermore, immunohistochemical analysis gave evidence that an upregulated expression of eNOS and CD31 in the copper peptide-functionalized RADA16 treated group. It can be envisioned that this scaffold can serve as a promising dressing for diabetic wound healing. This article is protected by copyright. All rights reserved.

Enhancement of DPP-IV inhibitory activity and the capacity for enabling GLP-1 secretion through RADA16-assisted molecular designed rapeseed peptide nanogels

The potential of pentapeptide IPQVS (RAP1) and octapeptide ELHQEEPL (RAP2) derived from rapeseed napin as natural dipeptidyl-peptidase IV (DPP-IV) inhibitors is promising. The objective was to develop a nanogel strategy to resist the hydrolysis of digestive and intestinal enzymes to enhance the DPP-IV inhibitory activity of RAP1 and RAP2, and stimulate glucagon-like peptide 1 (GLP-1) secretion of RAP2 by a RADA16-assisted molecular design. The linker of double Gly was used in the connection of RADA16 and the functional oligopeptide region (RAP1 and RAP2). Compared to the original oligopeptides, DPP-IV IC₅₀ of the nanogels RADA16-RAP1 and RADA16-RAP2 decreased by 26.43% and 17.46% in Caco-2 cell monolayers, respectively. The results showed that the two nanogel peptides with no toxicity to cells had higher contents of stable β-sheet structures (increased by 5.6-fold and 5.2-fold, respectively) than the original oligopeptides, and a self-assembled fibrous morphology. Rheological results suggested that the nanogels RADA16-RAP1 and RADA16-RAP2 exhibit good rheological properties for potential injectable applications; the storage modulus (G') was 10 times higher than the low modulus (G''). Furthermore, the RAP2 and its RADA16-assisted nanogel peptide at the concentration of 250 μM significantly (P < 0.05) increased the release of GLP-1 by 35.46% through the calcium-sensing receptor pathway in the enteroendocrine STC-1 cells. Hence, the innovative and harmless nanogels with the sequence of RADA16-GG-X_n have the potential for use by oral and injection administration for treating or relieving type 2 diabetes.

Facelift Patients Receiving Intraoperative Administration of a Self-assembling Hemostat Agent Experienced Minimal Bruising and No Acute Hematomas: A Pilot Study

Background

Hematomas are consistently cited as the most common complication of facelift surgery, with reported incidence rates ranging from 1% to 9% despite preventative measures. A self-assembling RADA16 peptide solution (PuraSinus, 3-D Matrix, Newton, MA) designed to aid in wound healing, adhesion prevention, and bleeding control has demonstrated hemostatic control of intra- and postoperative bleeding associated with various surgical procedures, including nasal and sinus surgery.

Objectives

To report surgical experience using novel application of RADA16 hemostatic agent in facelift procedures.

Methods

Through exploring incorporation of RADA16 hemostatic agent into standard of care, 15 higher-risk facelift patients were treated intraoperatively between December 2020 and July 2021. Postoperative follow-up was on post-procedure day 1 and 3 and at approximately one week. During follow-up, potential complications were assessed subjectively, including hematoma, swelling, and bruising; postoperative observations recorded; and photographs taken.

Results

Among facelift patients receiving intraoperative RADA16 hemostatic agent there were no hematomas or protracted ecchymosis events. The only significant complication was one patient admitted for intravenous hydration due to post-operative nausea and vomiting. All patients had minimal bruising or a dramatic absence of bruising and experienced no hemorrhage or hematoma. Through surgical experience, technique for RADA16 hemostatic agent placement was optimized and procedural details are provided.

Conclusions

Intraoperative administration of topical RADA16 hemostatic agent appears to deter acute hematoma and hemorrhage formation and early experience suggests that RADA16 hemostatic agent may also attenuate post-operative bruising in facelift patients. These observations warrant further investigation in a larger randomized controlled study.

Level of Evidence: 4

Biomimetic peptide nanoparticles participate in natural coagulation for hemostasis and wound healing

Uncontrolled hemorrhage is a major problem both in surgical intervention and after trauma. Herein, we design an in situ constructable peptide network, mimicking and participating in the native coagulation process for enhanced hemostasis and wound healing. The network consists of two peptides including C₆KL, mimicking platelets and C₆KG, mimicking fibrin. The C₆KL nanoparticles could bind to the collagen at the wound site and transform into C₆KL nanofibers. The C₆KG nanoparticles could bind to GPIIb/IIIa receptors on the surface of activated platelets and transform into C₆KG nanofibers. The in situ formed peptide network could interwind platelets, fibrin and red blood cells, causing embolism at the wound site. In a lethal femoral artery, vein, and nerve cut model of rats, the amount of bleeding was reduced to 32.8% by C₆KL and C₆KG with chitosan/alginate. The biomimetic peptides show great clinical potential as trauma hemostatic agents.

β-Sheet to Random Coil Transition in Self-Assembling Peptide Scaffolds Promotes Proteolytic Degradation

One of the most desirable properties that biomaterials designed for tissue engineering or drug delivery applications should fulfill is biodegradation and resorption without toxicity. Therefore, there is an increasing interest in the development of biomaterials able to be enzymatically degraded once implanted at the injury site or once delivered to the target organ. In this paper, we demonstrate the protease sensitivity of self-assembling amphiphilic peptides, in particular, RAD16-I (AcN-RADARADARADARADA-CONH2), which contains four potential cleavage sites for trypsin. We detected that when subjected to thermal denaturation, the peptide secondary structure suffers a transition from β-sheet to random coil. We also used Matrix-Assisted Laser Desorption/Ionization-Time-Of-Flight (MALDI-TOF) to detect the proteolytic breakdown products of samples subjected to incubation with trypsin as well as atomic force microscopy (AFM) to visualize the effect of the degradation on the nanofiber scaffold. Interestingly, thermally treated samples had a higher extent of degradation than non-denatured samples, suggesting that the transition from β-sheet to random coil leaves the cleavage sites accessible and susceptible to protease degradation. These results indicate that the self-assembling peptide can be reduced to short peptide sequences and, subsequently, degraded to single amino acids, constituting a group of naturally biodegradable materials optimal for their application in tissue engineering and regenerative medicine.

A Multi-Centre, Single-Arm Clinical Study to Confirm Safety and Performance of PuraStat®, for the Management of Bleeding in Elective Carotid Artery Surgery

Anastomotic bleeding in vascular surgery can be difficult to control. Patients, in particular those undergoing carotid surgery, have often been started on treatment with dual antiplatelet agents and receive systemic heparinization intraoperatively. The use of local hemostatic agents as an adjunct to conventional methods is widely reported. 3-D Matrix's absorbable hemostatic material RADA16 (PuraStat®), is a fully synthetic resorbable hemostatic agent. The aim of this study is to confirm the safety and performance of this agent when used to control intraoperative anastomotic bleeding during carotid endarterectomy (CEA). A prospective, single-arm, multicenter study involving 65 patients, undergoing CEA, in whom the hemostatic agent was applied to the suture line after removal of arterial clamps. Patients were followed up at 24 h, discharge, and one month after surgery. Time to hemostasis was measured as the primary endpoint. Secondary endpoints included hemostasis efficacy and safety outcomes, blood loss, intraoperative and postoperative administration of blood products, and incidence of reoperation for bleeding. A total of 65 cases (51 male and 14 female) undergoing CEA, utilizing patch reconstruction (90. 8%), eversion technique (6.1%), and direct closure (3.1%) were analyzed. All patients received dual antiplatelet therapy preoperatively and were administered systemic intravenous heparin intraoperatively, as per local protocol. The mean time to hemostasis was 83 s ± 105 s (95% CI: 55-110 s). Primary hemostatic efficacy was 90.8%. The mean volume of product used was 1.7 mL ± 1.1 mL. Hemostasis was achieved with a single application of the product in 49 patients (75.3%). Two patients required a transfusion of blood products intraoperatively. There were no blood product transfusions during the postoperative period. The intraoperative mean blood loss was 127 mL ± 111.4 mL and postoperatively, the total mean drainage volume was 49.0 mL ± 51.2 mL. The mean duration of surgery was 119 ± 35 min, and the mean clamp time was 35 min 12 s ± 19 min 59 s. In 90.8% of patients, there was no presence of hematoma at 24 h postoperatively. Three returned to theatre due to bleeding (2 in the first 24 h), however, none of these cases were considered product related. Overall, there were no device-related serious adverse events (SAE) or unanticipated device-related SAEs reported. Use of the hemostatic agent PuraStat® is associated with a high rate of hemostatic efficacy (90.8%) and a short time to hemostasis. The safety of the product for use on vascular anastomoses has been demonstrated.

Self-assembling peptide gels promote angiogenesis and functional recovery after spinal cord injury in rats

Spinal cord injury (SCI) leads to disruption of the blood–spinal cord barrier, hemorrhage, and tissue edema, which impair blood circulation and induce ischemia. Angiogenesis after SCI is an important step in the repair of damaged tissues, and the extent of angiogenesis strongly correlates with the neural regeneration. Various biomaterials have been developed to promote angiogenesis signaling pathways, and angiogenic self-assembling peptides are useful for producing diverse supramolecular structures with tunable functionality. RADA16 (Ac-RARADADARARADADA-NH2), which forms nanofiber networks under physiological conditions, is a self-assembling peptide that can provide mechanical support for tissue regeneration and reportedly has diverse roles in wound healing. In this study, we applied an injectable form of RADA16 with or without the neuropeptide substance P to the contused spinal cords of rats and examined angiogenesis within the damaged spinal cord and subsequent functional improvement. Histological and immunohistochemical analyses revealed that the inflammatory cell population in the lesion cavity was decreased, the vessel number and density around the damaged spinal cord were increased, and the levels of neurofilaments within the lesion cavity were increased in SCI rats that received RADA16 and RADA16 with substance P (rats in the RADA16/SP group). Moreover, real-time PCR analysis of damaged spinal cord tissues showed that IL-10 expression was increased and that locomotor function (as assessed by the Basso, Beattie, and Bresnahan (BBB) scale and the horizontal ladder test) was significantly improved in the RADA16/SP group compared to the control group. Our findings indicate that RADA16 modified with substance P effectively stimulates angiogenesis within the damaged spinal cord and is a candidate agent for promoting functional recovery post-SCI.

PuraStat RADA16 Self-Assembling Peptide Reduces Postoperative Abdominal Adhesion Formation in a Rabbit Cecal Sidewall Injury Model

Objective: To evaluate the effect of PuraStat (2.5% RADA16) administration on postoperative abdominal adhesion formation in an in vivo model.

Methods: Anesthetized New Zealand white rabbits underwent cecal sidewall abrasion surgery in which the cecal serosa and juxtaposed parietal peritoneum were abraded after access through an abdominal midline incision. Eight animals were randomized to receive PuraStat administration at the interface of the injured tissues before incision closure, and five animals served as untreated controls. Treated animals received 3–12 ml PuraStat solution per lesion. Animals were sacrificed 14 days after surgery and examined for adhesion formation at the wound site.

Results: At study terminus, adhesions were identified in 90% (9/10) of abraded cecum/peritoneal wound sites in untreated controls versus 25% (4/16) of PuraStat-treated sites (p = 0.004). Mean ± SD Total Adhesion Score (average of the values for extent + strength of the adhesion in both defects per animal; maximum score = 14 points) was significantly 76% lower in PuraStat-treated animals (2.0 ± 3.0 points) compared to untreated controls (8.2 ± 1.9 points) (p = 0.029). Mean adhesion coverage area of wound sites was 79% lower in PuraStat-treated animals than controls (p < 0.001), and mean adhesion durability was 72% lower in PuraStat-treated animals versus controls (p = 0.005). Remnant hydrogel was observed at the wound sites of 75% of treated animals at postoperative Day 14.

Conclusion: PuraStat treatment has a positive protective effect in the cecal sidewall injury model, and significantly reduces abdominal adhesion formation at the interface of the injured cecum and overlying peritoneal sidewall defect.

Self-Assembling Peptides: From Design to Biomedical Applications

Self-assembling peptides could be considered a novel class of agents able to harvest an array of micro/nanostructures that are highly attractive in the biomedical field. By modifying their amino acid composition, it is possible to mime several biological functions; when assembled in micro/nanostructures, they can be used for a variety of purposes such as tissue regeneration and engineering or drug delivery to improve drug release and/or stability and to reduce side effects. Other significant advantages of self-assembled peptides involve their biocompatibility and their ability to efficiently target molecular recognition sites. Due to their intrinsic characteristics, self-assembled peptide micro/nanostructures are capable to load both hydrophobic and hydrophilic drugs, and they are suitable to achieve a triggered drug delivery at disease sites by inserting in their structure's stimuli-responsive moieties. The focus of this review was to summarize the most recent and significant studies on self-assembled peptides with an emphasis on their application in the biomedical field.

Efficacy and histopathological effects of self-assembling peptides RADA16 and IEIK13 in neurosurgical hemostasis

There is a continued need for effective hemostatic agents that are safe for neurosurgical use. Self-assembling peptide hydrogels have been suggested as novel hemostatic agents. They offer some advantages for neurosurgical hemostasis (e.g., transparency), but their efficacy and safety for neurosurgery has not been established. In this paper, the efficacy and safety of two self-assembling peptides, RADA16 and IEIK13, are explored for hemostasis of oozing bleeding on the rat cerebral cortex (n=56). Chronic safety was evaluated by neuropathological evaluation at one, four, and twelve weeks after craniotomy (n=32). An inactive control and oxidized cellulose served as comparators. Mean time-to-hemostasis was significantly shorter for RADA16 and IEIK13 compared to controls, while safety evaluation yielded similar results. Histopathological response consisted primarily of macrophage infiltration at the lesion site in all groups. This study confirms the hemostatic potential and safety of RADA16 and IEIK13 for hemostasis in the rat brain.

Injectable self-assembling peptide nanofiber hydrogel as a bioactive 3D platform to promote chronic wound tissue regeneration

Chronic wounds remain a worldwide clinical challenge, and bioactive materials that can promote skin regeneration are required. Self-assembling peptide (SAP) hydrogels have shown great potential in tissue repair, but their regenerative efficacy and possible mechanism in chronic wound healing are unclear. Here, we report an SAP (KGH) that enhances extracellular matrix (ECM) remodeling and angiogenesis, thereby promoting chronic wound healing in diabetic mice. In vivo, the KGH hydrogel was retained in wounds up to 7 days after injection, and it was effective in speeding up wound closure by ∼20% compared to the control groups and enhancing angiogenesis (e.g., VEGFA, CD31⁺ capillaries), cell proliferation (e.g., PCNA⁺ cells), formation of granulation tissue (e.g., α-SMA), and ECM deposition/remodeling (e.g., collagen I, fibronectin). In vitro, the KGH hydrogel created a 3D microenvironment for skin cells, maintained the sustained growth of cell spheroids, and increased the secretion of ECM proteins (e.g., laminin) and growth factors (e.g., PDGFB, VEGFA, and TGF-β) in skin keratinocytes compared to the conventional 2D culture. Mechanistically, the KGH hydrogel might promote wound tissue regeneration by activating the Rho/ROCK and TGF-β/MEK/MAPK pathways. As a type of designed material, SAP can be further re-engineered with biological motifs, therapeutic reagents, or stem cells to enhance skin regeneration. This study highlights that SAP hydrogels are a promising material platform for advanced chronic wound healing and might have translational potential in future clinical applications. STATEMENT OF SIGNIFICANCE: Chronic wounds are a common and serious health issue worldwide, and bioactive dressing materials are required to address this issue. SAP hydrogels have shown certain tissue repair potential, but their regenerative efficacy and underlying mechanism in chronic wound healing remain elusive. Herein, we report that SAP hydrogels create a native 3D microenvironment that can remarkably stimulate angiogenesis and ECM remodeling in diabetic wounds. Mechanistically, the SAP hydrogel promoted ECM proteins and GFs secretion in skin cells through the activation of the Rho/ROCK and TGF-ß/MEK/MAPK pathways. Additionally, SAP can be readily engineered with various bioactive motifs or therapeutic drugs/cells. This work highlights SAP hydrogels as a promising biomaterial platform for chronic wound healing and the regeneration of many other tissues.

"PP-type" self-assembling peptides with superior rheological properties

The ionic-complementary self-assembling peptides discovered by Zhang Shuguang have solution-to-gel (sol-gel) transition capacity and one such peptide RADA16 has been commercialized into hemostatic agents. However, their sol-gel transition ability was not obvious because the peptide aqueous solution with a concentration greater than 1% w/v appeared to be thick and viscous. The current report describes PP-type self-assembling peptides. In addition to the ionic-complementary sequence, they have prolines at both ends of the sequence. This feature has led to better solubility, lower viscosity of the peptide solution, and simplified synthesis and purification processes while maintaining the great gelling performance of the ionic-complementary peptides. The PP-type peptides self-assembled into a well-organized nanofiber scaffold as shown by TEM. Among the PP-type peptides, the PRVDP9 sequence peptide was tested as a hemostatic agent and a mucosal elevating agent. The results were comparable to the classic RADA16. The PP-type self-assembling peptides have superior sol-gel transition ability. Therefore, it is predicted that they will be more suitable to be transported through catheters or endoscopes and have higher commercialization potential as compared with the classic self-assembling peptide sequences.

Self-assembling peptide haemostatic gel reduces incidence of pelvic collection after total mesorectal excision: Prospective cohort study

BACKGROUND

Pelvic surgery has the potential to leave behind a large raw surface, which can bleed and ooze postoperatively. The adoption of precision surgical approach for rectal cancers has led to reduction in blood loss. We aimed to assess 1) the feasibility and 2) the safety of using a self-assembling peptide (SAP) haemostatic agent (PuraStat®) after rectal cancer surgery to reduce the incidence of pelvic collections.

MATERIALS AND METHODS

This prospective cohort pilot study compared the results of 25 consecutive cases of total mesorectal excision (TME) with use of 5-10 ml of SAP, and 25 consecutive cases without PuraStat® application (CON, control group). The groups were compared for complications (Clavien-Dindo grade III and IV classification), postoperative drain output and length of hospital stay (LOS). Statistical analysis was carried out using paired samples T test and Fisher's exact test.

RESULTS

Fifty patients (SAP = 25, CON = 25) were enrolled into this study. Mean drain outputs (ml) on day 1, day 2 and day 3 were 60 ± 18, 89 ± 42 and 64 ± 45 in SAP group, and 102 ± 31, 95 ± 52, 66 ± 37 in CON group. This was significantly better for SAP group in day one after surgery. The mean LOS was shorter in SAP group (5.7 versus 7.4 days in CON, p 0.04). Clavien-Dindo III & IV complications were seen in two and five cases respectively (p 0.18). R0 resection rate (p 0.32) and lymph node harvest (p 0.13) were similar in both groups. There were no complications seen in relation to the application of the SAP.

CONCLUSIONS

These initial data suggest that SAP is a safe product, and feasible to apply in the pelvis after TME surgery. It appears to shorten the LOS and reduce the postoperative drain output and may reduce the incidence of Clavien-Dindo grade III & IV complications.