Current otolaryngologic applications of the novel self-assembling RADA-16 peptide matrix.

A novel bioresorbable agent on the market is PuraGel® (3-D Matrix, Tokyo, Japan), a RADA-16 product that acts as a synthetic hemostatic and space-filling gel that promotes wound healing and prevents adhesion formation. Given the reported benefits of accelerated wound healing and scar tissue prevention, there are multiple otolaryngologic applications where RADA-16 might improve outcomes. Our study highlights current utilization and associated post-operative complications with this product.

Transforming growth factor-ß1-loaded RADA-16 hydrogel scaffold for effective cartilage regeneration.

Cartilage repair remains a major challenge in clinical trials. These current cartilage repair materials can not effectively promote chondrocyte generation, limiting their practical application in cartilage repair. In this work, we develop an implantable scaffold of RADA-16 peptide hydrogel incorporated with TGF-ß1 to provide a microenvironment for stem cell-directed differentiation and chondrocyte adhesion growth. The longest release of growth factor TGF-ß1 release can reach up to 600 h under physiological conditions. TGF-ß1/RADA-16 hydrogel was demonstrated to be a lamellar porous structure. Based on the cell culture with hBMSCs, TGF-ß1/RADA-16 hydrogel showed excellent ability to promote cell proliferation, directed differentiation into chondrocytes, and functional protein secretion. Within 14 days, 80% of hBMSCs were observed to be directed to differentiate into vigorous chondrocytes in the co-culture of TGF-ß1/RADA-16 hydrogels with hBMSCs. Specifically, these newly generated chondrocytes can secrete and accumulate large amounts of collagen II within 28 days, which can effectively promote the formation of cartilage tissue. Finally, the exploration of RADA-16 hydrogel-based scaffolds incorporated with TGF-ß1 bioactive species would further greatly promote the practical clinical trials of cartilage remediation, which might have excellent potential to promote cartilage regeneration in areas of cartilage damage.

Self-assembling peptide hydrogel scaffold integrating stem cell-derived exosomes for infected bone defects.

Infected bone defect (IBD) is a great challenge in orthopedics, which involves in bone loss and infection. Here, a self-assembling hydrogel scaffold (named AMP-RAD/EXO), integrating antimicrobial peptides(AMPs), RADA16 and BMSCs exosomes with an innovative strategy, is developed and applied in IBD treatment for sustained antimicrobial ability, accelerating osteoblasts proliferation and promoting bone regeneration. AMPs present an excellent ability to inhibit infection, RADA16 is a self-assembling peptide hydrogel for AMPs delivery, and BMSCs exosomes can promote the bone regeneration. The prepared AMP-RAD/EXO exhibited a polyporous 3D structure for imbibition of BMSCs exosomes and migration of osteoblasts. In vitro studies indicate AMP-RAD/EXO can inhibit the growth of Staphylococcus aureus, accelerate the proliferation and migration of BMSCs. More importantly, in vivo results also prove that AMP-RAD/EXO exhibit an excellent effect on IBD treatment. Thus, the prepared AMP-RAD/EXO provides a multifunctional scaffold concept for bone tissue engineering technology.

Development and evaluation of RADA-PDGF2 self-assembling peptide hydrogel for enhanced skin wound healing.

Background: Wound healing complications affect numerous patients each year, creating significant economic and medical challenges. Currently, available methods are not fully effective in the treatment of chronic or complicated wounds; thus, new methods are constantly sought. Our previous studies showed that a peptide designated as PDGF2 derived from PDGF-BB could be a promising drug candidate for wound treatment and that RADA16-I can serve as a release system for bioactive peptides in wound healing. Based on that, in this work, we designed a new self-assembling hydrogel RADA-PDGF2, connecting both peptides by a sequence specific for neutrophil elastase, and evaluated its activity in wound healing. Methods: The physicochemical properties of the designed scaffold were analyzed using transmission electron microscopy, atomic force microscopy, cryoSEM microscopies, and circular dichroism spectroscopy. The enzymatic cleavage was performed using human neutrophil elastase and monitored using high-performance liquid chromatography and MS spectroscopic techniques. The aforementioned techniques (HPLC and MS) were also used to assess the stability of the peptide in water and human plasma. The biological activity was analyzed on human skin cells using a colorimetric XTT test, collagen synthesis evaluation, and a migration assay. The biocompatibility was analyzed with LDH cytotoxicity assay and flow cytometric analysis of activation of immune cells. Finally, RADA-PDGF2 activity in wound healing was checked in a mouse dorsal skin injury model. Results: The analysis showed that RADA-PDGF2 can self-assemble, form a hydrogel, and release a bioactive sequence when incubated with human elastase. It shows pro-proliferative and pro-migratory properties and accelerates wound closure in the mouse model compared to RADA16-I. In addition, it is not cytotoxic to human cells and does not show immunogenicity. RADA-PDGF2 seems to be a promising drug candidate for wound management.

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.

A Novel Airway-Organoid Model Based on a Nano-Self-Assembling Peptide: Construction and Application in Adenovirus Infection Studies.

Purpose: Hydrogels containing the nano-self-assembling peptide RADA16-I (Nanogels) were utilized as scaffolds to establish airway organoids and an adenovirus-infected model. The results support in vitro adenovirus studies, including isolation and culture, pathogenesis research, and antiviral drug screening. Methods: HSAEC1-KT, HuLEC-5a and HELF cells were cocultured in RADA16-I hydrogel scaffolds to construct an airway organoid model. Adenovirus was used to infect this model for adenovirus-related studies. The morphological characteristics and the proliferation and activity of airway organoids before and after adenovirus infection were evaluated. The expression of the airway organoid marker proteins CC10, KRT8, AQP5, SPC, VIM and CD31 was detected. TEM and qPCR were used to detect adenovirus proliferation in airway organoids. Results: HSAEC1-KT, HuLEC-5a and HELF cells cocultured at 10:7:2 self-assembled into airway organoids and maintained long-term proliferation in a RADA16-I hydrogel 3D culture system. The organoids stably expressed the lumen-forming protein KRT8 and the terminal airway markers AQP5 and SPC. Adenoviruses maintained long-term proliferation in this model. Conclusion: An airway-organoid model of adenovirus infection was constructed in vitro from three human lung-derived cell lines on RADA16-I hydrogels. The model has potential as a novel research tool for adenovirus isolation and culture, pathogenesis research, and antiviral drug screening.

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.

Bacillus subtilis RadA/Sms-Mediated Nascent Lagging-Strand Unwinding at Stalled or Reversed Forks Is a Two-Step Process: RadA/Sms Assists RecA Nucleation, and RecA Loads RadA/Sms.

Replication fork rescue requires Bacillus subtilis RecA, its negative (SsbA) and positive (RecO) mediators, and fork-processing (RadA/Sms). To understand how they work to promote fork remodeling, reconstituted branched replication intermediates were used. We show that RadA/Sms (or its variant, RadA/Sms C13A) binds to the 5'-tail of a reversed fork with longer nascent lagging-strand and unwinds it in the 5'→3' direction, but RecA and its mediators limit unwinding. RadA/Sms cannot unwind a reversed fork with a longer nascent leading-strand, or a gapped stalled fork, but RecA interacts with and activates unwinding. Here, the molecular mechanism by which RadA/Sms, in concert with RecA, in a two-step reaction, unwinds the nascent lagging-strand of reversed or stalled forks is unveiled. First, RadA/Sms, as a mediator, contributes to SsbA displacement from the forks and nucleates RecA onto single-stranded DNA. Then, RecA, as a loader, interacts with and recruits RadA/Sms onto the nascent lagging strand of these DNA substrates to unwind them. Within this process, RecA limits RadA/Sms self-assembly to control fork processing, and RadA/Sms prevents RecA from provoking unnecessary recombination.

Divalent metal cofactors differentially modulate RadA-mediated strand invasion and exchange in Saccharolobus solfataricus.

Central to the universal process of recombination, RecA family proteins form nucleoprotein filaments to catalyze production of heteroduplex DNA between substrate ssDNAs and template dsDNAs. ATP binding assists the filament in assuming the necessary conformation for forming heteroduplex DNA, but hydrolysis is not required. ATP hydrolysis has two identified roles which are not universally conserved: promotion of filament dissociation and enhancing flexibility of the filament. In this work, we examine ATP utilization of the RecA family recombinase SsoRadA from Saccharolobus solfataricus to determine its function in recombinase-mediated heteroduplex DNA formation. Wild-type SsoRadA protein and two ATPase mutant proteins were evaluated for the effects of three divalent metal cofactors. We found that unlike other archaeal RadA proteins, SsoRadA-mediated strand exchange is not enhanced by Ca2+. Instead, the S. solfataricus recombinase can utilize Mn2+ to stimulate strand invasion and reduce ADP-binding stability. Additionally, reduction of SsoRadA ATPase activity by Walker Box mutation or cofactor alteration resulted in a loss of large, complete strand exchange products. Depletion of ADP was found to improve initial strand invasion but also led to a similar loss of large strand exchange events. Our results indicate that overall, SsoRadA is distinct in its use of divalent cofactors but its activity with Mn2+ shows similarity to human RAD51 protein with Ca2+.

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.

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.

RadA, a Key Gene of the Circadian Rhythm of Escherichia coli.

Circadian rhythms are present in almost all living organisms, and their activity relies on molecular clocks. In prokaryotes, a functional molecular clock has been defined only in cyanobacteria. Here, we investigated the presence of circadian rhythms in non-cyanobacterial prokaryotes. The bioinformatic approach was used to identify a homologue of KaiC (circadian gene in cyanobacteria) in Escherichia coli. Then, strains of E. coli (wild type and mutants) were grown on blood agar, and sampling was made every 3 h for 24 h at constant conditions. Gene expression was determined by qRT-PCR, and the rhythmicity was analyzed using the Cosinor model. We identified RadA as a KaiC homologue in E. coli. Expression of radA showed a circadian rhythm persisting at least 3 days, with a peak in the morning. The circadian expression of other E. coli genes was also observed. Gene circadian oscillations were lost in radA mutants of E. coli. This study provides evidence of molecular clock gene expression in E. coli with a circadian rhythm. Such a finding paves the way for new perspectives in antibacterial treatment.

Human Adipose-Derived Stem Cells Combined with Nano-Hydrogel Promote Functional Recovery after Spinal Cord Injury in Rats.

The treatment of spinal cord injury aims to reconstruct the fiber connection and restore the interrupted neural pathways. Adipose mesenchymal stem cells (ADSCs) can promote the recovery of motor functions in spinal cord injury. However, poor survival of ADSCs and leakage outside of the injury site after local transplantation reduce the number of cells, which seriously attenuates the cumulative effect. We performed heterotopic transplantation on rats with severe spinal cord injury using human ADSCs loaded within self-assembly hydrogel RADA16-RGD (R: arginine; A: alanine; D: aspartic acid; G: glycine). Our results indicate that the combined transplantation of human ADSCs with RADA16-RGD improved the survival of ADSCs at the injured site. The inflammatory reaction was inhibited, with improved survival of the neurons and increased residual area of nerve fibers and myelin protein. The functional behaviors were promoted, as determined by the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale score and electrophysiological measurements. ADSCs can promote the repair of spinal cord injury. This study provides new ideas for the treatment of spinal cord injury.

The use of self-assembling peptides (PuraStat) for hemostasis in cervical endocrine surgery. A real-life case series of 353 patients.

INTRODUCTION: Cervical endocrine surgery is frequent and carries the risk of rare but potentially life-threatening bleeding complications. Energy-based devices for stopping bleeding are not always usable in contact with nerves or parathyroid glands. Topical hemostatic agents may be an additional resource. PuraStat™, made of the self-assembling peptide RADA16, forms a new category of topical hemostatic agents. OBJECTIVE: To assess the performance and safety of PuraStat to achieve hemostasis in cervical endocrine surgery. METHODS: A retrospective chart review over four years was performed on 353 patients undergoing thyroidectomy and/or parathyroidectomy by a single senior surgeon, using PuraStat at the end of surgery in contact with recurrent nerves and parathyroid glands. RESULTS: 353 patients (79.06% female, mean age 54 years) underwent surgery with six weeks follow-up visit. Three patients had revision surgery for hematoma within the first 4 h (0.84%), which is within the low ranges reported in the literature. There was no delayed bleeding after 24 h, and dysphonia was observed in 15 patients, more severe for 2 patients (one unilateral and one bilateral palsy), and transient for the other 13 patients suggesting no product-related damage to the recurrent nerves. Hypocalcemia with clinical signs were reported in 8 cases. There were no unexpected adverse events. CONCLUSION: This is the first report of the use of PuraStat in patients undergoing cervical endocrine surgery, showing high performance and safety in achieving hemostasis and in preventing delayed bleeding without damage to the recurrent nerves. Further randomized controlled studies are needed to confirm the results.

The Effect of RADA16-I and CDNF on Neurogenesis and Neuroprotection in Brain Ischemia-Reperfusion Injury.

Scaffold materials, neurotrophic factors, and seed cells are three elements of neural tissue engineering. As well-known self-assembling peptide-based hydrogels, RADA16-I and modified peptides are attractive matrices for neural tissue engineering. In addition to its neuroprotective effects, cerebral dopamine neurotrophic factor (CDNF) has been reported to promote the proliferation, migration, and differentiation of neural stem cells (NSCs). However, the role of RADA16-I combined with CDNF on NSCs remains unknown. First, the effect of RADA16-I hydrogel and CDNF on the proliferation and differentiation of cultured NSCs was investigated. Next, RADA16-I hydrogel and CDNF were microinjected into the lateral ventricle (LV) of middle cerebral artery occlusion (MCAO) rats to activate endogenous NSCs. CDNF promoted the proliferation of NSCs, while RADA16-I induced the neural differentiation of NSCs in vitro. Importantly, both RADA16-I and CDNF promoted the proliferation, migration, and differentiation of endogenous NSCs by activating the ERK1/2 and STAT3 pathways, and CDNF exerted an obvious neuroprotective effect on brain ischemia-reperfusion injury. These findings provide new information regarding the application of the scaffold material RADA16-I hydrogel and the neurotrophic factor CDNF in neural tissue engineering and suggest that RADA16-I hydrogel and CDNF microinjection may represent a novel therapeutic strategy for the treatment of stroke.

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.

Covid-19 as occupational disease in healthcare workers: a brief review of cases in the Clinical Hospital Centre Rijeka, Croatia.

The coronavirus disease 19 (COVID-19) pandemic has had a tremendous impact on every facet of private life and work organisation in virtually all social and economic sectors worldwide. People who stand on the first line of defence are healthcare workers (HCWs) risking exposure to infected patients. However, even though they are often affected by COVID-19 and associated somatic and mental health problems, COVID-19 as a new illness was not immediately acknowledged as occupational disease. This is why several groups of HCWs contacted their occupational medicine physicians in 2020 with a request to register the infection with SARS-CoV-2 as occupational disease. In an attempt to support their appeals and show that hospital workers have a high occupational risk of COVID-19, this study presents COVID-19 incidence and symptoms in 100 employees working at 11 clinics of the Clinical Hospital Centre (CHC) Rijeka, Croatia from 1 June to end December 2020. All of them were infected with SARS-CoV-2 and took sick leave, which lasted 13.6±2.6 days in average. This study also looks into the role of occupational medicine physicians in prospective monitoring of acute and long-acting consequences of COVID-19 that might occur in HCWs.

Experimental anti-tumor effect of emodin in suspension - in situ hydrogels formed with self-assembling peptide.

Lung cancer is a major cause of cancer-related deaths worldwide. Stimulus-sensitive hydrogels, which can be formed by responding to stimuli in the cancer microenvironment, have been widely studied as controlled-release carriers for hydrophobic anticancer drugs. In this study, self-assembling peptide RADA16-I was used to encapsulate the hydrophobic drug emodin (EM) under magnetic stirring to form a colloidal suspension, and the colloidal suspension (RADA16-I-EM) was introduced into environments with physiological pH/ionic strength to form hydrogels in situ. The results showed that RADA16-I had good cell compatibility and the RADA16-I-EM in situ hydrogels can obviously reduce the toxicity of EM to normal cells. In addition, compared with free EM (in water suspensions without peptide) at equivalent concentrations, RADA16-I-EM in situ hydrogels significantly reduced the survival fraction of LLC lung cancer cells, while increased the uptake of EM by the cells, and it also induced apoptosis and cell cycle arrest in the G2/M phase more significantly and reduced the migration, invasion, and clone abilities of the cells in vitro. The RADA16-I-EM in situ hydrogels also showed better cancer growth inhibition effects in cancer models (mice bearing LLC cells xenograft cancer), which induced cell apoptosis in the cancer tissue and reduced the toxic side effects of EM on normal tissues and organs in vivo compared with the free EM. It was revealed that RADA16-I can be exploited as a promising carrier for hydrophobic anticancer drugs and has the potential to improve the administration of anticancer drugs to treat cancer effectively with enhanced chemotherapy.

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

RADA16 is a synthetic peptide that exists as a viscous solution in an acidic formulation. In an acidic aqueous environment, the peptides spontaneously self-assemble into ß-sheet nanofibers. Upon exposure and buffering of RADA16 solution to the physiological pH of biological fluids such as blood, interstitial fluid and lymph, the nanofibers begin physically crosslinking within seconds into a stable interwoven transparent hydrogel 3-D matrix. The RADA16 nanofiber hydrogel structure closely resembles the 3-dimensional architecture of native extracellular matrices. These properties make RADA16 formulations ideal topical hemostatic agents for controlling bleeding during surgery and to prevent post-operative rebleeding. A commercial RADA16 formulation is currently used for hemostasis in cardiovascular, gastrointestinal, and otorhinolaryngological surgical procedures, and studies are underway to investigate its use in wound healing and adhesion reduction. Straightforward application of viscous RADA16 into areas that are not easily accessible circumvents technical challenges in difficult-to-reach bleeding sites. The transparent hydrogel allows clear visualization of the surgical field and facilitates suture line assessment and revision. The shear-thinning and thixotropic properties of RADA16 allow its easy application through a narrow nozzle such as an endoscopic catheter. RADA16 hydrogels can fill tissue voids and do not swell so can be safely used in close proximity to pressure-sensitive tissues and in enclosed non-expandable regions. By definition, the synthetic peptide avoids potential microbiological contamination and immune responses that may occur with animal-, plant-, or mineral-derived topical hemostats. In vitro experiments, animal studies, and recent clinical experiences suggest that RADA16 nanofibrous hydrogels can act as surrogate extracellular matrices that support cellular behavior and interactions essential for wound healing and for tissue regenerative applications. In the future, the unique nature of RADA16 may also allow us to use it as a depot for precisely regulated drug and biopharmaceutical delivery.

Self-assembling peptides: From a discovery in a yeast protein to diverse uses and beyond.

Well-defined nanofiber scaffold hydrogels made of self-assembling peptides have found their way into various 3D tissue culture and clinical products. I reflect initial puzzlement of the unexpected discovery, gradual understanding of how these peptides undergo self-assembly, to eventually translating designer biological scaffolds into commercial products. Peptides are ubiquitous in nature and useful in many fields. They are found as hormones, pheromones, antibacterial, and antifungal agents in innate immunity systems, toxins, as well anti-inset pesticides. However, the concept of peptides as materials was not recognized until 1990 when a self-assembling peptide as a repeating segment in a yeast protein was serendipitously discovered. The peptide materials have bona fide materials properties and are made from simple amino acids with well-ordered nanostructures under physiological conditions. Some current applications include: (a) Real 3D tissue cell cultures of diverse tissue cells and various stem cells; (b) reparative and regenerative medicine as well as tissue engineering; (c) 3D tissue printing; (d) sustained releases of small molecules, growth factors and monoclonal antibodies; and (e) accelerated wound healing of skin and diabetic ulcers as well as instant hemostasis in surgery. Self-assembling peptide nanobiotechnology will likely continue to expand in many directions in the coming years. I will also briefly introduce my current research using a simple QTY code for membrane protein design. I am greatly honored and humbled to be invited to contribute an Award Winner Recollection of the 2020 Emil Thomas Kaiser Award from the Protein Society.