Self-assembling Peptide Hydrogels Research Articles

Development and Characterization of Nanoscale Gel-Core Liposomes Using a Short Self-Assembled Peptide Hydrogel: Implications for Drug Delivery

Development and Characterization of Nanoscale Gel-Core Liposomes Using a Short Self-Assembled Peptide Hydrogel: Implications for Drug Delivery

PEG-SH-GNPs-SAPNS@miR-29a delivery system promotes neural regeneration and recovery of motor function after spinal cord injury

Spinal cord injury (SCI) is a serious disease characterized by hemorrhage, edema, local ischemia and hypoxia, inflammatory reaction, and degeneration of the injured spinal cord, which lacks effective clinical treatments. We design a PEG-SH-GNPs-SAPNS@miR-29a delivery system to repair impaired spinal cord by building a regenerative microenvironment for the recruitment of endogenous neural stem cells. The miR-29a, as an axonal regeneration-related miRNA that overexpression of miR-29a significantly inhibits the expression of PTEN and promotes axonal regeneration of the injured spinal cord. The gold nanoparticles and self-assembling peptide hydrogel composite scaffold (PEG-SH-GNPs-SAPNS@miR-29a delivery system) applied to deliver miR-29a, which recruit endogenous neural stem cells simultaneously. Sustained release of miR-29a and recruitment of endogenous neural stem cells give rise to favorable axonal regeneration and recovery of motor function after spinal cord injury. These findings suggest that the PEG-SH-GNPs-SAPNS@miR-29a delivery system may be an alternative strategy for the treatment of SCI.

Synthesis of pH/ temperature sensitive gelatin/peptide composite hydrogels and its characterization for potential controlled drug release applications

Conventional self-assembled peptide hydrogels have poor mechanical properties and tend to release abruptly when they are used as drug carriers, limiting the application of these materials in biomedical field. In this work, gelatin was embedded in a pH-responsive peptide Ac-FALNLAKD-NH2 (PEP) to construct gelatin/peptide composite hydrogels (Gel/PEP) for controlling the delivery of the anticancer drug chelerythrine (CHE). The physicochemical properties of Gel/PEP composite hydrogels were evaluated. The results of circular dichroism and Fourier transform infrared spectroscopy characterization showed that compared with PEP hydrogels and gelatin, the Gel/PEP composite hydrogel has a superposition of two secondary structures, in which β-sheet and random coil accounted for 44.7 % and 55.3 % of the conformation, respectively. Rheology and scanning electron microscope characterization confirmed that the Gel/PEP hydrogel has a highly dense nanofibrous meshwork structure, which enhances mechanical and injectable properties. In addition, the encapsulation rate of CHE could reach more than 97 % at a gelatin/peptide mass ratio of 7:1. More importantly, in vitro results showed that the composite hydrogel still had good pH and thermal response performance, which can achieve controlled release of CHE. Therefore, it is possible to synthesize supramolecular drug release soft materials by composite of gelatin and peptide hydrogels.

Successful hemostasis and subsequent cannulation using a self-assembling peptide hydrogel for bleeding after precut sphincterotomy.

Successful hemostasis and subsequent cannulation using a self-assembling peptide hydrogel for bleeding after precut sphincterotomy.

Delivery of Porphyrins Through Self-Assembling Peptide Hydrogels for Accelerated Healing of Experimental Skin Defects In Vivo.

The care and healing of skin defects resulting from different causes has been the object of research to achieve rapid and complete skin regeneration. Hydrogels have been used for their ability to maintain hydration during wound healing, absorb wound exudate, and cover the underlying tissue without adherence while being transparent. In this study, we evaluated the efficacy of a hydrogel (H) with encapsulated porphyrin (H+P) on a rat model of surgically-induced skin defects. Four round 6 mm diameter skin defects were performed under general anesthesia on the dorsal area of 24 three-month-old "Young" and 24 twelve-month-old "Mature" male rats. Each age group was separated into the Control, H, and H+P groups, n=8 each, where no therapy, H, or H+P was respectively applied daily for 20 days. Digital photographs and skin biopsies were taken on the third, seventh, 10th, and 20th postoperative days and evaluated by planimetry, histology, and immunohistochemistry. Planimetry results demonstrated significantly decreased perimeter, diameter, and area measurements (p<0.005) of group H+P compared to Control and H groups on days 10 and 20 in the young rats, while in the mature rats, the significant differences were evident earlier (perimeter third day p<0.05; diameter and area seventh day p<0.05 and p<0.005, respectively vs. H). Granulation and scar tissue formation were also reduced in the H+P groups although they were not statistically significant. The application of H+P on the skin defects benefited the healing process in both young and mature animal groups, as evidenced by the statistically significant findings of planimetry. The beneficial healing process was more pronounced in the mature animals, both in the level of statistical significance as well as regarding time (evident already on the third day of healing), probably due to porphyrin assisting the reduced healing rate, which is observed in organisms of advanced age.

Gold nanoparticles-decorated peptide hydrogel for antifouling electrochemical dopamine determination.

A reliable and brief ultralow fouling electrochemical sensing system capable of monitoring targets in complex biological media was constructed and validated based on gold nanoparticles-peptide hydrogel-modified screen-printed electrode. The self-assembled zwitterionic peptide hydrogel was prepared by a newly designed peptide sequence of Phe-Phe-Cys-Cys-(Glu-Lys)3 with the N-terminal modified with a fluorene methoxycarbonyl group. The thiol groups on cysteine of the designed peptide are able to self-assemble with AuNPs to form a three-dimensional nanonetwork structure, which showed satisfactory antifouling capability in complex biological media (human serum). The developed gold nanoparticles-peptide hydrogel-based electrochemical sensing platform displayed notably sensing properties for dopamine determination, with a wide linear range (from 0.2 nM to 1.9 μM), a low limit of detection (0.12 nM), and an excellent selectivity. This highly sensitive and ultralow fouling electrochemical sensor was fabricated via simple preparation with concise components that avoid the accumulation of layers with single functional material and complex activation processes. This ultralow fouling and highly sensitive strategy based on the gold nanoparticles-peptide hydrogel with a three-dimensional nanonetwork offers a solution to the current situation of various low-fouling sensing systems facing impaired sensitivity and provides a potential path for the practical application of electrochemical sensors.

Sustained delivery of IL-10 by self-assembling peptide hydrogel to reprogram macrophages and promote diabetic alveolar bone defect healing.

Delayed regeneration of alveolar bone defects because of prolonged inflammation under diabetic conditions remains a challenge for dental rehabilitation in clinic, and effective therapies are required. Cytokines-based immuotherapies might be a potential strategy to regulate inflammation and bone regeneration. Here, we report that local delivery of interleukin-10 (IL-10) by injectable self-assembling peptide (SAP) hydrogel is efficient to promote proinflammatory (M1)-to-anti-inflammatory (M2) phenotype conversion, thereby enhancing bone regeneration in diabetic alveolar bone defects. Characteristics of SAP hydrogel were evaluated by morphology, injectable and rheological properties. The loading and release of IL-10 from the SAP hydrogel were evaluated over time in culture. The local inflammatory response and bone repair efficacy of the SAP/IL-10 hydrogel was evaluated in vivo using an alveolar bone defect model of diabetic mice. Finally, the direct effects of M2 macrophage on M1 phenotype and mineralization of MSCs were investigated. In vitro, encapsulated IL-10 could be sustainedly released by SAP hydrogel with preserved bioactivities. In vivo, SAP/IL-10 hydrogel showed significantly higher efficacy to attenuate M1 polarization and proinflammatory factors levels, and enhance expressions of osteogenic factors. As a result, diabetic bone regeneration induced by SAP/IL-10 hydrogel was significantly faster. Mechanistically, M2 macrophages induced by sustained IL-10 delivery might promote diabetic bone regeneration by reprogramming M1 phenotype, suppressing local inflammation and enhancing the osteogenic differentiation of mesenchymal stem cells (MSCs). This study highlights that the SAP hydrogel is a promising drug delivery platform for treatment of alveolar bone defects, which might have translational potential in future clinical applications.

Successful hemostasis using a self-assembling peptide hydrogel for bleeding after endoscopic papillary large-balloon dilation.

Adverse bleeding events can occur after endoscopic papillary large-balloon dilation (EPLBD) [1], though not as frequently as after endoscopic sphincterotomy. Post-EPLBD bleeding often originates from sites deeper than the bile duct orifice, such as lacerations of the bile duct wall, and the origin of bleeding may not be identified; therefore, it is often difficult to stop the bleeding. A novel self-assembling peptide hydrogel (PuraStat; 3-D Matrix, Tokyo, Japan) was recently developed as a hemostatic agent [2] [3] [4]. We present a case of hemostasis of massive post-EPLBD bleeding achieved with this hydrogel.

Preparation of Hydrogel Composites Using a Sustainable Approach for In Situ Silver Nanoparticles Formation.

The recognized antibacterial properties of silver nanoparticles (AgNPs) characterize them as attractive nanomaterials for developing new bioactive materials less prone to the development of antibiotic resistance. In this work, we developed new composites based on self-assembling Fmoc-Phe3 peptide hydrogels impregnated with in situ prepared AgNPs. Different methodologies, from traditional to innovative and eco-sustainable, were compared. The obtained composites were characterized from a hydrodynamic, structural, and morphological point of view, using different techniques such as DLS, SEM, and rheological measurements to evaluate how the choice of the reducing agent determines the characteristics of AgNPs and how their presence within the hydrogel affects their structure and properties. Moreover, the antibacterial properties of these composites were tested against S. aureus, a major human pathogen responsible for a wide range of clinical infections. Results demonstrated that the hydrogel composites containing AgNPs (hgel@AgNPs) could represent promising biomaterials for treating S. aureus-related infections.

Multifunctional Self-Assembled Peptide Hydrogels for Biomedical Applications.

Self-assembly is a growth mechanism in nature to apply local interactions forming a minimum energy structure. Currently, self-assembled materials are considered for biomedical applications due to their pleasant features, including scalability, versatility, simplicity, and inexpensiveness. Self-assembled peptides can be applied to design and fabricate different structures, such as micelles, hydrogels, and vesicles, by diverse physical interactions between specific building blocks. Among them, bioactivity, biocompatibility, and biodegradability of peptide hydrogels have introduced them as versatile platforms in biomedical applications, such as drug delivery, tissue engineering, biosensing, and treating different diseases. Moreover, peptides are capable of mimicking the microenvironment of natural tissues and responding to internal and external stimuli for triggered drug release. In the current review, the unique characteristics of peptide hydrogels and recent advances in their design, fabrication, as well as chemical, physical, and biological properties are presented. Additionally, recent developments of these biomaterials are discussed with a particular focus on their biomedical applications in targeted drug delivery and gene delivery, stem cell therapy, cancer therapy and immune regulation, bioimaging, and regenerative medicine.

Long-term cultures of human pancreatic islets in self-assembling peptides hydrogels.

Human pancreatic islets transplantation is an experimental therapeutic treatment for Type I Diabetes. Limited islets lifespan in culture remains the main drawback, due to the absence of native extracellular matrix as mechanical support after their enzymatic and mechanical isolation procedure. Extending the limited islets lifespan by creating a long-term in vitro culture remains a challenge. In this study, three biomimetic self-assembling peptides were proposed as potential candidates to recreate in vitro a pancreatic extracellular matrix, with the aim to mechanically and biologically support human pancreatic islets, by creating a three-dimensional culture system. The embedded human islets were analyzed for morphology and functionality in long-term cultures (14-and 28-days), by evaluating β-cells content, endocrine component, and extracellular matrix constituents. The three-dimensional support provided by HYDROSAP scaffold, and cultured into MIAMI medium, displayed a preserved islets functionality, a maintained rounded islets morphology and an invariable islets diameter up to 4 weeks, with results analogues to freshly-isolated islets. In vivo efficacy studies of the in vitro 3D cell culture system are ongoing; however, preliminary data suggest that human pancreatic islets pre-cultured for 2weeks in HYDROSAP hydrogels and transplanted under subrenal capsule may restore normoglycemia in diabetic mice. Therefore, engineered self-assembling peptide scaffolds may provide a useful platform for long-term maintenance and preservation of functional human pancreatic islets in vitro.

Hydrogel-Based Pre-Clinical Evaluation of Repurposed FDA-Approved Drugs for AML.

In vivo models of acute myeloid leukemia (AML) are low throughput, and standard liquid culture models fail to recapitulate the mechanical and biochemical properties of the extracellular matrix-rich protective bone marrow niche that contributes to drug resistance. Candidate drug discovery in AML requires advanced synthetic platforms to improve our understanding of the impact of mechanical cues on drug sensitivity in AML. By use of a synthetic, self-assembling peptide hydrogel (SAPH) of modifiable stiffness and composition, a 3D model of the bone marrow niche to screen repurposed FDA-approved drugs has been developed and utilized. AML cell proliferation was dependent on SAPH stiffness, which was optimized to facilitate colony growth. Three candidate FDA-approved drugs were initially screened against the THP-1 cell line and mAF9 primary cells in liquid culture, and EC50 values were used to inform drug sensitivity assays in the peptide hydrogel models. Salinomycin demonstrated efficacy in both an 'early-stage' model in which treatment was added shortly after initiation of AML cell encapsulation, and an 'established' model in which time-encapsulated cells had started to form colonies. Sensitivity to Vidofludimus treatment was not observed in the hydrogel models, and Atorvastatin demonstrated increased sensitivity in the 'established' compared to the 'early-stage' model. AML patient samples were equally sensitive to Salinomycin in the 3D hydrogels and partially sensitive to Atorvastatin. Together, this confirms that AML cell sensitivity is drug- and context-specific and that advanced synthetic platforms for higher throughput are valuable tools for pre-clinical evaluation of candidate anti-AML drugs.

Ultralong hydroxyapatite nanowires-incorporated dipeptide hydrogel with enhanced mechanical strength and superior in vivo osteogenesis activity

Self-assembling peptide hydrogels have attracted considerable interest in tissue engineering for their biocompatibility, biodegradability, low immunogenicity, facile modification, and similarity to the native extracellular matrix. However, they still suffer from weak mechanical strength and lack of specific bioactivity. Ultralong hydroxyapatite nanowires (UHANWs) are synthesized to work as a reinforcement agent similar to the steel bars in the reinforced concrete to co-assemble with dipeptide nanofibers, endowing the hybrid hydrogel with enhancing and controllable mechanical properties. Furthermore, additional factors BMP-2 can be introduced into the hydrogel to improve its bioactivity. The experimental results show that the incorporation of UHANWs into the hydrogel matrix leads to an obvious increase in the storage modulus of scaffolds, exhibiting good biocompatibility and bioactivity. The hybrid hydrogels can facilitate the proliferation and osteogenetic differentiation of cells on their surface. The in vivo evaluation reveals that bone defects implanted with the as-designed hydrogel scaffolds show enhanced bone regeneration activity, implying their great potential in biomedical fields.

Inhibition of Self-Assembling Peptide Fibrils Formation Using Thioflavin T as a Photosensitizer

Misfolded proteins produce fibrillar aggregates, which contain β-sheet higher order structures. The oligomers, protofibrils, and fibrils generated during protein aggregation process are cytotoxic and can cause various neurodegenerative diseases. Recently the photo-active materials, the photosensitizers, have attracted increased attention in the study and treatment of amyloid-related diseases. Here, we studied the photodynamic effect of the amyloid-specific fluorescence dye Thioflavin T on the formation of self-assembled peptide hydrogel. It was demonstrated that the gelation process under irradiation inhibits significantly, at that the structural and mechanical properties of mature fibrils change notably suggesting that ThT could be regarded as a theranostic probe. The developed peptide model allows for quantification of the photodynamic agent’s efficiency in preventing aggregation, thus paving the way for a high-throughput test system for screening of light-responsive theranostic agents.

Repair of critical-sized rat cranial defects with RADA16-W9 self-assembled peptide hydrogel

Bone defects are common in orthopaedics and there is an urgent need to explore effective bone repair materials with osteoinductive activity. Peptide self-assembled nanomaterials have a fibrous structure like that of the extracellular matrix and are ideal bionic scaffold materials. In this study, a short peptide WP9QY (W9) with strong osteoinductive effect was tagged to a self-assembled peptide RADA16 molecule through solid phase synthesis to design a RADA16-W9 peptide gel scaffold. A rat cranial defect was used as a research model to explore the effect of this peptide material on the repair of bone defects in vivo. The structure characteristic of the functional self-assembling peptide nanofiber hydrogel scaffold RADA16-W9 was evaluated by atomic force microscopy (AFM). Then adipose stem cells (ASCs) were isolated from Sprague-Dawley (SD) rat and cultured. the cellular compatibility of scaffold was evaluated through Live/Dead assay. Furthermore, we explore the effects of hydrogels in vivo with the critical-sized mouse calvarial defect model. Micro-CT analysis showed that the RADA16-W9 group had higher levels of bone volume/total volume (BV/TV) (P < 0.05)，Trabecular number(TB.N) (P < 0.05)，bone mineral density (BMD)(P < 0.05) and trabecular thickness (Tb. Th) (P < 0.05) compared with the RADA16 and PBS groups. Hematoxylin and eosin (H&E) staining showed that RADA16-W9 group had the highest bone regeneration level. Histochemical staining showed significantly higher expression levels of osteogenic factors such as alkaline phosphatase (ALP) and osteocalcin (OCN) in the RADA16-W9 group than in the other two groups (P < 0.05). Reverse transcription polymerase chain reaction (RT-PCR) quantification showed higher mRNA expression levels of osteogenic-related genes ALP, Runt-related transcription factor 2(Runx2), OCN, Osteopontin (OPN) in the RADA16-W9 group than in the RADA16 and PBS groups (P < 0.05). The live/dead staining results showed that RADA16-W9 is not toxic to rASCs and has good biocompatibility. In vivo experiments show that it accelerates the process of bone reconstruction, significantly promoting bone regeneration and can be used to develop a molecular drug for bone defect repair.

Three-dimensional Culture Using Atelocollagen Sponge and Self-assembling Peptide Hydrogel.

This study aimed to assess the combined application of two biomaterials, a selfassembling peptide hydrogel (SPH) and an atelocollagen sponge (ACS). The ACS was combined with SPH (PuraMatrixⓇ or PanaceaGelⓇ) and its osteogenic effects on mouse osteoblastic cell line MC3T3 then evaluated. Each type of SPH was successfully incorporated into the ACS. The MC3T3 cells showed uniform distribution within the scaffold. No necrotic cells were observed throughout the experimental procedures. When the SPH was combined with the ACS, the MC3T3 cells differentiated toward the osteo-lineage, expressing Alp, Runx2, Osx, Bsp, and Oc. PanaceaGelⓇ exhibited a stronger osteogenic effect on the cells than PuraMatrixⓇ.

A comparison of fixation methods for SEM analysis of self-assembling peptide hydrogel nanoarchitecture.

Determining the porosity of hydrogels is an important component of material characterisation. While scanning electron microscopy (SEM) is a widely used method to study hydrogel nanoarchitecture, it is well-established that SEM sample preparation methods can alter the structure of hydrogels. Herein we describe the impact of sample preparation on the SEM analysis of self-assembling β-peptide hydrogels. Three methods of hydrogel preparation for SEM were compared, and each method preserved distinctly different nanoarchitecture, specifically, different levels of fibre alignment and porosity. Comparison of conventional SEM preparation and our hybrid method, which comprises high pressure freezing, freeze substitution without fixative and critical point drying, showed a high degree of similarity at the nanometre scale and diverging architecture at the micron scale. This study quantified the impact of chemical fixation versus high pressure freezing on self-assembling β3-peptide hydrogels, demonstrated the effect of sample preparation on fibre alignment and porosity, and presents a novel hybrid preparation method where chemical fixation can be avoided when conventional SEM is desired.

A novel peptide hydrogel of metal ion clusters for accelerating bone defect regeneration.

In the absence of adequate treatment, effective bone regeneration remains a great challenge. Exploring hydrogels with properties of excellent bioactivity, stability, non-immunogenicity, and commercialization is an important step to develop hydrogel-based bone regeneration materials. In this study, we engineered a self-assembled chelating peptide hydrogel loaded with an osteogenic metal ion cluster extracted from the processed pyritum decoction, including Fe2+, Cu2+, Zn2+, Mn2+, Mg2+, and Ca2+ ions, named processed pyritum hydrogel (PPH). We demonstrated that as a reservoir of beneficial metal ion clusters in bone regeneration, PPH has been shown to regulate a variety of genes in the process of bone regeneration. These genes are mainly involved in extracellular matrix synthesis, cell adhesion and migration, cytokine expression, antimicrobial and inflammation. Therefore, PPH accelerated the progress of various bone healing stages, and shortened the bone healing cycle by 4weeks. Our investigation outcomes showed that the engineered metal ion cluster hydrogel is a novel, simple, and commercializable bone-regenerating hydrogel with potential clinical use.

Nitric oxide-generating self-assembling peptide hydrogel coating for enhancing hemocompatibility of blood-contacting devices

Thrombosis is the major stumbling block to the clinical application of blood-contacting devices. Herein, a quick and easy surface engineering strategy of hydrogel coating with the therapeutic gas nitric oxide (NO) generation was reported to realize up-regulation of cyclic guanosine monophosphate (cGMP) and improve hemocompatibility for diverse metal materials. We first introduce the active centre selenocysteine of glutathione peroxidase (GPx) to the self-assembling peptide (RADA)4, obtaining a functionalized hydrogel. Then the hydrogel is directly coated on the 316L stainless steel (SS) for catalytically generating NO from endogenous s-nitrosothiols (RSNO). The generated NO endows the coated surface with regulation of platelet behavior and reduction of plasmatic coagulation activation and complement system activation, hence improving antithrombotic ability in vitro and ex vivo. Overall, our NO-generating hydrogel coating surface engineering strategy provides a novel solution to remove the obstacle about thrombosis of blood-contacting devices in clinic.

Remodeling Microenvironment for Endogenous Repair through Precise Modulation of Chondroitin Sulfate Proteoglycans Following Spinal Cord Injury.

The fluid-filled cystic cavity sealed by a dense scar developed following traumatic spinal cord injury (SCI) has been a major obstacle to neural regeneration and functional recovery. Here the transected lesion is bridged using a functional self-assembling peptide (F-SAP) hydrogel loaded with membrane-permeable intracellular sigma peptide (ISP) and intracellular LAR peptide (ILP), targeted at perturbing chondroitin sulfate proteoglycan (CSPG) inhibitory signaling. As compared to F-SAP hydrogel loaded with chondroitinase ABC, the F-SAP+ISP/ILP promotes a beneficial anti-inflammatory response via manipulation of microglia/macrophages infiltration and assembly of extracellular matrix (ECM) molecules into fibrotic matrix rather than scarring tissues. The remodeled ECM creates a permissive environment that supports axon regrowth and the formation of synaptic connections with neurons derived from endogenous neural stem cells. The remodeled networks contribute to functional recovery, as demonstrated by improved hind limb movements and electrophysiological properties. This work proposes a unique mechanism that ECM remodeling induced by CSPG-manipulation-based anti-inflammation can construct a permissive environment for neural regeneration, and shed light on the advancement of manipulation of cascading cellular and molecular events potential for endogenous repair of SCI.