Designer D-form self-assembling peptide scaffolds promote the proliferation and migration of rat bone marrow-derived mesenchymal stem cells

Real-Space Visualization of Charged Polymer Network of Hydrogel by Double Network Strategy and Mineral Staining

Hydrogels consist of three-dimensional (3D) and complicated polymer networks that determine their physical properties. Among the methods for structural analyses of hydrogels, the real-space imaging of a polymer network of hydrogels on a nanometer scale is one of the optimal methods; however, it is highly challenging. In this study, we propose a direct observation method for cationic polymer networks using transmission electron microscopy (TEM). By combining the double network strategy and the mineral staining technique, we overcame the challenges of polymer aggregation and the low electron density of the polymer. An objective cationic network was incorporated into a neutral skeleton network to suppress shrinkage during subsequent staining. Titania mineralization along the cationic polymer strands provided sufficient electron density for the objective polymer network for TEM observation. This observation method enables the visualization of local structures in real space and plays a complementary role to scattering methods for soft matter structure analysis.

Self-Assembled Food Peptides: Recent Advances and Perspectives in Food and Health Applications

Self-assembling peptides are rapidly gaining attention as novel biomaterials for food and biomedical applications. Peptides self-assemble when triggered by physical or chemical factors due to their versatile physicochemical characteristics. Peptide self-assembly, when combined with the health-promoting bioactivity of peptides, can also result in a plethora of biofunctionalities of the biomaterials. This perspective highlights current developments in the use of food-derived self-assembling peptides as biomaterials, bioactive nutraceuticals, and potential dual functioning bioactive biomaterials. Also discussed are the challenges and opportunities in the use of self-assembling bioactive peptides in designing biocompatible, biostable, and bioavailable multipurpose biomaterials.

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.

Peptide-Based Hydrogels: Template Materials for Tissue Engineering

Tissue and organ regeneration are challenging issues, yet they represent the frontier of current research in the biomedical field. Currently, a major problem is the lack of ideal scaffold materials' definition. As well known, peptide hydrogels have attracted increasing attention in recent years thanks to significant properties such as biocompatibility, biodegradability, good mechanical stability, and tissue-like elasticity. Such properties make them excellent candidates for 3D scaffold materials. In this review, the first aim is to describe the main features of a peptide hydrogel in order to be considered as a 3D scaffold, focusing in particular on mechanical properties, as well as on biodegradability and bioactivity. Then, some recent applications of peptide hydrogels in tissue engineering, including soft and hard tissues, will be discussed to analyze the most relevant research trends in this field.

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.

Encapsulation of human endometrial stem cells in chitosan hydrogel containing titanium oxide nanoparticles for dental pulp repair and tissue regeneration in male Wistar rats

This study aimed to determine the impact of human endometrial stem cells (EnSCs) and titanium oxide nanoparticles (TiO₂ NPs) on dental pulp repair and regeneration in an animal model through dentine development and tissue regeneration. The EnSCs were put on a three-dimensional (3D) chitosan scaffold containing TiO₂ NPs after obtaining and purifying the collagenase enzyme. Pulps were exposed on the maxillary left first molar of all rats followed by direct pulp capping with the experimental scaffolds, as follows. Groups were: 1, control group without any treatment; 2, chitosan group (CS); 3, chitosan group with stem cells (CS/SCs); 4, chitosan group with stem cells and TiO₂ NPs (CS/EnSCs/TiO₂). Glass ionomer was used as a sealant in all groups. The teeth were extracted and histologically evaluated after 8 weeks. The quality and amount of dentine in the CS/EnSCs/TiO₂ group were higher than in the other groups. The combination of EnSCs with TiO₂ NPs and 3D chitosan scaffolds had a synergistic effect on each other, evidencing increased speed and quality of dentine formation. Using EnSCs with TiO₂ NPs on a 3D chitosan scaffold can be a suitable combination for direct pulp capping and dentine regeneration in a rat molar tooth model.

An amelogenin-based peptide hydrogel promoted the odontogenic differentiation of human dental pulp cells

Amelogenin can induce odontogenic differentiation of human dental pulp cells (HDPCs), which has great potential and advantages in dentine-pulp complex regeneration. However, the unstability of amelogenin limits its further application. This study constructed amelogenin self-assembling peptide hydrogels (L-gel or D-gel) by heating-cooling technique, investigated the effects of these hydrogels on the odontogenic differentiation of HDPCs and explored the underneath mechanism. The critical aggregation concentration, conformation, morphology, mechanical property and biological stability of the hydrogels were characterized, respectively. The effects of the hydrogels on the odontogenic differentiation of HDPCs were evaluated via alkaline phosphatase activity measurement, quantitative reverse transcription polymerase chain reaction, western blot, Alizarin red staining and scanning electron microscope. The mechanism was explored via signaling pathway experiments. Results showed that both the L-gel and D-gel stimulated the odontogenic differentiation of HDPCs on both Day 7 and Day 14, while the D-gel showed the highest enhancement effects. Meanwhile, the D-gel promoted calcium accumulation and mineralized matrix deposition on Day 21. The D-gel activated MAPK-ERK1/2 pathways in HDPCs and induced the odontogenic differentiation via ERK1/2 and transforming growth factor/smad pathways. Overall, our study demonstrated that the amelogenin peptide hydrogel stimulated the odontogenic differentiation and enhanced mineralization, which held big potential in the dentine-pulp complex regeneration.

Supramolecular Peptide Nanofiber Hydrogels for Bone Tissue Engineering: From Multihierarchical Fabrications to Comprehensive Applications

Bone tissue engineering is becoming an ideal strategy to replace autologous bone grafts for surgical bone repair, but the multihierarchical complexity of natural bone is still difficult to emulate due to the lack of suitable biomaterials. Supramolecular peptide nanofiber hydrogels (SPNHs) are emerging biomaterials because of their inherent biocompatibility, satisfied biodegradability, high purity, facile functionalization, and tunable mechanical properties. This review initially focuses on the multihierarchical fabrications by SPNHs to emulate natural bony extracellular matrix. Structurally, supramolecular peptides based on distinctive building blocks can assemble into nanofiber hydrogels, which can be used as nanomorphology-mimetic scaffolds for tissue engineering. Biochemically, bioactive motifs and bioactive factors can be covalently tethered or physically absorbed to SPNHs to endow various functions depending on physiological and pharmacological requirements. Mechanically, four strategies are summarized to optimize the biophysical microenvironment of SPNHs for bone regeneration. Furthermore, comprehensive applications about SPNHs for bone tissue engineering are reviewed. The biomaterials can be directly used in the form of injectable hydrogels or composite nanoscaffolds, or they can be used to construct engineered bone grafts by bioprinting or bioreactors. Finally, continuing challenges and outlook are discussed.

Chirality-induced bionic scaffolds in bone defects repair-a review

Due to lack of amino sugar with aging, people will suffer from various epidemic bone diseases called "undead cancer" by the World Health Organization. The key problem in bone tissue engineering that has not been completely resolved is the repair of critical large-scale bone and cartilage defects. The chirality of the extracellular matrix plays a decisive role in the physiological activity of bone cells and the occurrence of bone tissue, but the mechanism of chirality in regulating cell adhesion and growth is still in the early stage of exploration. This paper reviews the application progress of chirality-induced bionic scaffolds in bone defects repair based on "soft" and "hard" scaffolds. The aim is to summarize the effects of different chiral structures (L-shaped and D-shaped) in the process of inducing bionic scaffolds in bone defects repair. In addition, many technologies and methods as well as issues worthy of special consideration for preparing chirality-induced bionic scaffolds are also introduced. We expect that this work can provide inspiring ideas for designing new chirality-induced bionic scaffolds and promote the development of chirality in bone tissue engineering. This article is protected by copyright. All rights reserved.

Improvement of Rat Spinal Cord Injury Following Lentiviral Vector-Transduced Neural Stem/Progenitor Cells Derived from Human Epileptic Brain Tissue Transplantation with a Self-assembling Peptide Scaffold

Spinal cord injury (SCI) is a disabling neurological disorder that causes neural circuit dysfunction. Although various therapies have been applied to improve the neurological outcomes of SCI, little clinical progress has been achieved. Stem cell-based therapy aimed at restoring the lost cells and supporting micromilieu at the site of the injury has become a conceptually attractive option for tissue repair following SCI. Adult human neural stem/progenitor cells (hNS/PCs) were obtained from the epileptic human brain specimens. Induction of SCI was followed by the application of lentiviral vector-mediated green fluorescent protein-labeled hNS/PCs seeded in PuraMatrix peptide hydrogel (PM). The co-application of hNS/PCs and PM at the SCI injury site significantly enhanced cell survival and differentiation, reduced the lesion volume, and improved neurological functions compared to the control groups. Besides, the transplanted hNS/PCs seeded in PM revealed significantly higher migration abilities into the lesion site and the healthy host tissue as well as a greater differentiation into astrocytes and neurons in the vicinity of the lesion as well as in the host tissue. Our data suggest that the transplantation of hNS/PCs seeded in PM could be a promising approach to restore the damaged tissues and improve neurological functions after SCI.

A novel biocomposite scaffold with antibacterial potential and the ability to promote bone repair

Clinical treatment of bone defects caused by trauma, tumor resection and other bone diseases, especially bone defects that can lead to infection, remains a major challenge. Currently, autologous bone implantation is the gold standard for treatment of bone defects, but it is limited by secondary trauma and insufficient autologous material. Moreover, postoperative infection is an important factor affecting bone healing.AcN-RADARADARADARADA-CONH2 (RADA) is a new type of self-assembling peptide(SAP) composed of Arg,Ala,Asp and other amino acids was designed and prepared. The "RADA" self-assembling peptide hydrogels has excellent biological activity and it's completely biodegradable and non-toxic.It is also have been confirmed to promote cell proliferation, wound healing, tissue repair, and drug delivery. To promote bone regeneration and simultaneously prevent bacterial infection, we designed biocomposite scaffolds comprising RADA and calcium phosphate cement (CPC), termed RADA-CPC. The morphological features of the scaffold were characterized by scanning electron microscopy (SEM). In vitro studies demonstrated that RADA-CPC enhances osteoblast proliferation, differentiation and mineralization. In addition, the scaffold was used as a drug delivery system to treat postoperative infections by sustained release of ciprofloxacin (CIP). The RADA-CPC scaffold may have potential application prospects in orthopedics field because of its role in promoting bone repair and as a sustained-release drug carrier to prevent infections.

Synthetic peptide hydrogels as 3D scaffolds for tissue engineering

The regeneration of tissues and organs poses an immense challenge due to the extreme complexity in the research work involved. Despite the tissue engineering approach being considered as a promising strategy for more than two decades, a key issue impeding its progress is the lack of ideal scaffold materials. Nature-inspired synthetic peptide hydrogels are inherently biocompatible, and its high resemblance to extracellular matrix makes peptide hydrogels suitable 3D scaffold materials. This review covers the important aspects of peptide hydrogels as 3D scaffolds, including mechanical properties, biodegradability and bioactivity, and the current approaches in creating matrices with optimized features. Many of these scaffolds contain peptide sequences that are widely reported for tissue repair and regeneration and these peptide sequences will also be discussed. Furthermore, 3D biofabrication strategies of synthetic peptide hydrogels and the recent advances of peptide hydrogels in tissue engineering will also be described to reflect the current trend in the field. In the final section, we will present the future outlook in the design and development of peptide-based hydrogels for translational tissue engineering applications.

Delivery of MSCs with a Hybrid β-Sheet Peptide Hydrogel Consisting IGF-1C Domain and D-Form Peptide for Acute Kidney Injury Therapy

Purpose

By providing a stem cell microenvironment with particular bioactive constituents in vivo, synthetic biomaterials have been progressively successful in stem cell-based tissue regeneration by enhancing the engraftment and survival of transplanted cells. Designs with bioactive motifs to influence cell behavior and with D-form amino acids to modulate scaffold stability may be critical for the development and optimization of self-assembling biomimetic hydrogel scaffolds for stem cell therapy.

Materials and Methods

In this study, we linked naphthalene (Nap) covalently to a short D-form peptide (Nap-^DF^DFG) and the C domain of insulin-like growth factor-1 (IGF-1C) as a functional hydrogel-based scaffolds, and we hypothesized that this hydrogel could enhance the therapeutic efficiency of human placenta-derived mesenchymal stem cells (hP-MSCs) in a murine acute kidney injury (AKI) model.

Results

The self-assembling peptide was constrained into a classical β-sheet structure and showed hydrogel properties. Our results revealed that this hydrogel exhibited increased affinity for IGF-1 receptor. Furthermore, cotransplantation of the β-IGF-1C hydrogel and hP-MSCs contributed to endogenous regeneration post-injury and boosted angiogenesis in a murine AKI model, leading to recovery of renal function.

Conclusion

This hydrogel could provide a favorable niche for hP-MSCs and thereby rescue renal function in an AKI model by promoting cell survival and angiogenesis. In conclusion, by covalently linking the desired functional groups to D-form peptides to create functional hydrogels, self-assembling β-sheet peptide hydrogels may serve as a promising platform for tissue-engineering and stem cell therapy.

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Multicomponent hydrogels for the formation of vascularized bone-like constructs in vitro

The native extracellular matrix (ECM) is a complex gel-like system with a broad range of structural features and biomolecular signals. Hydrogel platforms that can recapitulate the complexity and signaling properties of this ECM would have enormous impact in fields ranging from tissue engineering to drug discovery. Here, we report on the design, synthesis, and proof-of-concept validation of a microporous and nanofibrous hydrogel exhibiting multiple bioactive epitopes designed to recreate key features of the bone ECM. The material platform integrates self-assembly with orthogonal enzymatic cross-linking to create a supramolecular environment comprising hyaluronic acid modified with tyramine (HA-Tyr) and peptides amphiphiles (PAs) designed to promote cell adhesion (RGDS-PA), osteogenesis (Osteo-PA), and angiogenesis (Angio-PA). Through individual and co-cultures of human adipose derived mesenchymal stem cells (hAMSCs) and human umbilical vascular endothelial cells (HUVECs), we confirmed the capacity of the HA-Tyr/RGDS-PA/Osteo-PA/Angio-PA hydrogel to promote cell adhesion as well as osteogenic and angiogenic differentiation in both 2D and 3D setups. Furthermore, using immunofluorescent staining and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), we demonstrated co-differentiation and organization of hAMSCs and HUVECs into 3D aggregates resembling vascularized bone-like constructs. STATEMENT OF SIGNIFICANCE: This body of work presents a new approach to develop more complex, yet functional, in vitro environments for cell culture while enabling a high level of control, tuneability, and reproducibility. The multicomponent self-assembling bioactive 2D and 3D hydrogels with nanofibrous architecture designed to recreate key molecular and macromolecular features of the native bone ECM and promote both osteogenesis and angiogenesis. The materials induce endothelial cells towards large vascular lumens and MSCs into bone cells on/within the same platform and form vascularized-bone like construct in vitro. This strategy looks encouraging for lifelike bone tissue engineering in vitro and bone tissue regeneration in vivo.

Silymarin effect on experimental bone defect repair in rat following implantation of the electrospun PLA/carbon nanotubes scaffold associated with Wharton's jelly mesenchymal stem cells

In this study, the ability of silymarin to heal rat calvarial bone critical defects with mesenchymal stem cells isolated from human Wharton's jelly (HWJMSC) cultured on the electrospun scaffold of poly (lactic acid)/carbon nanotube (PLA/CNT) has been examined. In this study, 20 adult male Wistar rats were divided into four groups of five each. Under general anesthesia, 8 mm defects were created in the calvarial bone of the rats. Then, study groups were defined as no treatment group, the scaffold alone, the scaffold and HWJMSCs, and the scaffold/cells plus oral silymarin, respectively. The histomorphometric study was performed using H&E staining and Goldner's Masson trichrome as specific staining. The results of this study showed that the electrospun PLA/CNT scaffold is a biocompatible scaffold and HWJMSCs can considerably attach and proliferate on this scaffold, and the scaffold itself is also a suitable option for improving the bone repair process. The results of the histomorphometric analysis also showed a significantly higher amount of recently formed bone in the silymarin group plus scaffold/cells compared to the scaffold and cell group alone (p < .05). Utilizing silymarin plus HWJMSCs cultured on PLA/CNT scaffold can be used as a suitable method for the process of osteogenesis and bone repair.

Controlled release of basic fibroblast growth factor from a peptide biomaterial for bone regeneration

Self-assembled peptide scaffolds based on D-RADA16 are an important matrix for controlled drug release and three-dimensional cell culture. In this work, D-RADA16 peptide hydrogels were coated on artificial bone composed of nano-hydroxyapatite/polyamide 66 (nHA/PA66) to obtain a porous drug-releasing structure for treating bone defects. The developed materials were characterized via transmission electron microscopy and scanning electron microscopy. The proliferation and adhesion of bone mesenchymal stem cells (BMSCs) were examined by confocal laser microscopy and CCK-8 experiments. The osteogenic ability of the porous materials towards bone BMSCs was examined in vitro by staining with Alizarin Red S and alkaline phosphatase, and bioactivity was evaluated in vivo. The results revealed that nHA/PA66/D-RADA16/bFGF reduces the degradation rate of D-RADA16 hydrogels and prolongs sustained release of bFGF, which would promote BMSCs proliferation, adhesion and osteogenesis in vitro and bone repair in vivo. Thus, it deserves more attention and is worthy of further research.

Effect of Chirality on Cell Spreading and Differentiation: From Chiral Molecules to Chiral Self-Assembly

The influence of chirality on cell behavior is closely related with relevant biological events; however, many recent studies only focus on the apparent chiral influence of supramolecular nanofibers and ignore the respective effects of molecular chirality and supramolecular chirality in biological processes. Herein, the inherent molecular and supramolecular chiral effects on cell spreading and differentiation are studied. Left-handed nanofibers (referring to supramolecular chirality) assembled from l-amino acid derivatives can enhance cell spreading and proliferation compared to flat l-surfaces (referring to molecular chirality). However, compared to the d-surfaces (referring to molecular chirality), right-handed nanofibers (referring to supramolecular chirality) derived from d-amino acid suppress cell spreading and proliferation, overturning the conventional view that a fibrous morphology generally enhances cell adhesion. The results directly suggest that the amplification of chirality from chiral molecules to chiral assemblies significantly enhances the effect on regulated cell behavior by supramolecular helical handedness. Moreover, cell differentiation is found to be chirality dependent. It suggests that both the l-amino acid derivatives and the left-handed fibers facilitate osteogenic differentiation. This study provides useful insight into understanding the origin of chiral expression from the molecular to the macroscopic level in nature.

Coupling synthetic biology and programmable materials to construct complex tissue ecosystems

Synthetic biology combines engineering and biology to produce artificial systems with programmable features. Specifically, engineered microenvironments have advanced immensely over the past few decades, owing in part to the merging of materials with biological mimetic structures. In this review, we adapt a traditional definition of community ecology to describe "cellular ecology", or the study of the distribution of cell populations and interactions within their microenvironment. We discuss two exemplar hydrogel platforms: (1) self-assembling peptide (SAP) hydrogels and (2) Poly(ethylene) glycol (PEG) hydrogels and describe future opportunities for merging smart material design and synthetic biology within the scope of multicellular platforms.

Self-assembling injectable peptide hydrogels for emerging treatment of ischemic stroke

Ischaemic stroke remains one of the leading causes of death and disability worldwide, without any long-term effective treatments targeted at regeneration. This has led to developments of novel, biomaterial-based strategies using self-assembling peptide hydrogels.

Paclitaxel-loaded pH responsive hydrogel based on self-assembled peptides for tumor targeting

Intratumoral delivery of chemotherapeutic agents may permit the localization of drugs in tumors, decrease nonspecific targeting and increase efficacy.

Sustained Release of Antimicrobial Peptide from Self-Assembling Hydrogel Enhanced Osteogenesis

Biomaterials have been widely used in bone infection and osteomyelitis resulting from their versatile functionalities. As far as we know, the appearance of osteomyelitis was mainly caused by bacteria. Therefore, a biomaterial that can cure bone infection and promote osteogenesis may become an ideal candidate for the treatment of osteomyelitis. Cationic antimicrobial peptides (AMPs) have been proved to have an excellent ability to kill bacteria, fungi, viruses, and parasites. However, the application of AMPs in bone infection and osteomyelitis is quite limited. Here, we designed a new hydrogel that has an inhibitory effect on the proliferation of S. aureus and enhances osteogenesis. RADA16 self-assembling peptide has been applied for AMPs delivery. In this study, we demonstrated that RADA16 could form a stable structure and afford the sustained release of AMPs. The interwoven nanofiber morphology was detected by field emission scanning electron microscopy. The sustained release study revealed that the release of AMPs could be obtained until 28 days. In vitro research showed this new self-assembling hydrogel could promote the proliferation of bone mesenchymal stem cells (BMSCs) and inhibited the growth of S. aureus. More importantly, the results in vivo also proved that RADA16-AMP self-assembling peptide had an excellent effect on bone formation. Our findings implied that we successfully combined RADA16 and AMPs together and laid the foundation for the application of this new hydrogel and open new avenues for biomaterials.

Amphiphilic peptides as novel nanomaterials: design, self-assembly and application

Designer self-assembling peptides are a category of emerging nanobiomaterials which have been widely investigated in the past decades. In this field, amphiphilic peptides have received special attention for their simplicity in design and versatility in application. This review focuses on recent progress in designer amphiphilic peptides, trying to give a comprehensive overview about this special type of self-assembling peptides. By exploring published studies on several typical types of amphiphilic peptides in recent years, herein we discuss in detail the basic design, self-assembling behaviors and the mechanism of amphiphilic peptides, as well as how their nanostructures are affected by the peptide characteristics or environmental parameters. The applications of these peptides as potential nanomaterials for nanomedicine and nanotechnology are also summarized.

Amyloid-like staining property of RADA16-I nanofibers and its potential application in detecting and imaging the nanomaterial

Background

Designer self-assembling peptide nanofibers (SAPNFs) as a novel kind of emerging nanomaterial have received more and more attention in the field of nanomedicine in recent years. However, a simple method to monitor and image SAPNFs is still currently absent.

Methods

RADA16-I, a well-studied ionic complementary peptide was used as a model to check potential amyloid-like staining properties of SAPNFs. Thioflavin-T (ThT) and Congo red (CR) as specific dyes for amyloid-like fibrils were used to stain RADA16-I nanofibers in solution, combined with drugs or cells, or injected in vivo as hydrogels. Fluorescent spectrometry and fluorescent microscopy were used to check ThT-binding property, and polarized light microscopy was used to check CR-staining property.

Results

ThT binding with the nanofibers showed enhanced and blue-shifted fluorescence, and specific apple-green birefringence could be observed after the nanofibers were stained with CR. Based on these properties we further showed that ThT-binding fluorescence intensity could be used to monitor the forming and changing of nanofibers in solution, while fluorescent microscopy and polarized light microscopy could be used to image the nanofibers as material for drug delivery, 3D cell culture, and tissue regeneration.

Conclusion

Our results may provide convenient and reliable tools for detecting SAPNFs, which would be helpful for understanding their self-assembling process and exploring their applications.