Slow release of molecules in self-assembling peptide nanofiber scaffold

Excipient Induced Unusual Phase Separation in Bovine Serum Albumin Solution: An Explicit Role Played by Ion-Hydration

We report an instantaneous room-temperature phase separation of 1 mM bovine serum albumin solution in the presence of (20% acetic acid+0.2 M NaCl), a routinely used food preservative; an opaque liquid-like phase (L) coexists in equilibrium with a granular gel like phase (G). Interestingly, neither 20% acetic acid nor 0.2 M NaCl individually induces such a phase separation. Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) imaging show aggregated proteins to be dispersed in the upper phase, while the lower phase is composed of cross-linked fibrils (hydrogels). Mid-IR FTIR, Raman scattering, and circular dichroism (CD) experiments reveal a significant increase in the β-sheet content in BSA, which confirms the formation of amyloids in the presence of the excipient. Both L and G phases undergo distinct visual and microscopic changes upon incubation at 25 and 80 °C. It is evident that the added salt plays a pivotal role in bringing about this otherwise unique phase behavior. We divulge the explicit role of the ion associated hydration using THz-FTIR measurements in the 1.5-16.7 THz (50-550 cm-1) frequency window. Systematic alteration in the ion-induced THz-active mode of water envisions the key role of ions in shaping the various phases. Our study depicts an intriguing observation of severe amyloidosis of BSA upon the addition of a food preservative, even at room temperature, which is expected to add new insight into amyloid research. Considering the increasing number of individuals suffering from several neurodegenerative disorders (Alzheimer's, Parkinson's, type-2 diabetes, obesity, cancer, etc.), this study leads a caution toward critically revisiting the usage of known food preservatives.

Probing the Effects of Chirality on Self-Assembling Peptides: Hydrogel Formation, Degradation, Antigen Release, and Adjuvancy

Introduction

Multidomain peptides (MDPs) are amino acid sequences that self-assemble to form supramolecular hydrogels under physiological conditions that have shown promise for a number of biomedical applications. K2(SL)6K2 ("K2"), a widely studied MDP, has demonstrated the ability to enhance the humoral immune response to co-delivered antigen. Herein, we sought to explore the in vitro and in vivo properties of a peptide with the same sequence but opposite chirality (D-K2) since peptides composed of D-amino acids are resistant to protease degradation and potentially more immunostimulatory than their canonical counterparts.

Methods

K2 and D-K2 hydrogels were characterized and evaluated in vitro using circular dichroism, rheology, cryo-electron microscopy, and fluorescence recovery after photobleaching studies. In vivo experiments in SKH-1 mice were conducted to evaluate both ovalbumin release from the hydrogels and hydrogel degradation. The injection site of the hydrogels was analyzed using histology and humoral immunity was assessed by ELISA.

Results

In vitro, the enantiomeric hydrogels exhibited similar rheological properties, and fluorescence recovery after photobleaching experiments demonstrated that the diffusion of ovalbumin (OVA), a model antigen, was similar within both hydrogels. In vivo, K2 and D-K2 peptide hydrogels had similar OVA release rates, both releasing 89% of the antigen within 8 days. Both hydrogels elicited a similar antigen-specific humoral immune response. However, the in vivo degradation of the D-K2 hydrogel progressed significantly slower than K2. After 4 weeks in vivo, only 23 ± 7% of the K2 hydrogel remained at the injection site compared to 94 ± 7% of the D-K2 hydrogel, likely due to their different protease susceptibilities.

Conclusion

Taken together, these data suggest that peptide chirality can be a useful tool for increasing hydrogel residence time for biomedical applications that would benefit from long persistence times and that, if an antigen releases over a sufficiently short period, release can be largely independent of degradation rate, though slower-diffusing payloads may exhibit degradation rate dependence.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00806-1.

A co-assembly process for high strength and injectable dual network gels with sustained doxorubicin release performance

Adopting a non-covalent co-assembly strategy shows great potential in loading drugs efficiently and safely in drug delivery systems. However, finding an efficient method for developing high strength gels with thixotropic characteristics is still challenging. In this work, by hybridizing the low molecular weight gelator fluorenylmethyloxycarbonyl-phenylalanine (Fmoc-F) (first single network, 1st SN) and alginate (second single network, 2nd SN) into a dual network (DN) gel, gels with high strength as well as thixotropy were prepared efficiently. The DN gels showed high strength (103 Pa in SN gels and 105 Pa in DN gels) and thixotropic characteristics (yield strain <25%; recovery ratio >85% within 100 seconds). The application performance was verified by loading doxorubicin (DOX), showing better encapsulation capacity (77.06% in 1st SN, 59.11% in 2nd SN and 96.71% in DN) and sustained release performance (lasting one week under physiological conditions) than single network gels. Experimental and DFT results allowed the elaboration of the specific non-covalent co-assembly mechanism for DN gel formation and DOX loading. The DN gels were formed by co-assembly driven by H-bond and π-π stacking interactions and then strengthened by Ca2+-coupling. Most DOX molecules co-assembled with Fmoc-F and alginate through π-π stacking and H-bond interactions (DOX-I), with a few free DOX molecules (DOX-II) left. Proven by the release dynamics test, DOX was released through a diffusion-erosion process, in an order of DOX-I first and then DOX-II. This work suggests that non-covalent co-assembly is a useful technique for effective material strengthening and drug delivery.

Biotechnological applications of amyloid fibrils

Protein aggregates and amyloid fibrils have special qualities and are used in a variety of biotechnological applications. They are extensively employed in bioremediation, biomaterials, and biocatalysis. Because of their capacity to encapsulate and release pharmaceuticals and their sensitivity to certain molecules, respectively, they are also used in drug delivery and biosensor applications. They have also demonstrated potential in the domains of food and bioremediation. Additionally, amyloid peptides have drawn interest in biological applications, especially in the investigation of illnesses like Parkinson's and Alzheimer's. The unique characteristics of amyloid fibrils, namely their mechanical strength and β-sheet structure, make them adaptable to a wide range of biotechnological uses. Even with their promise, one important factor to keep in mind before widely using modified amyloid materials is their potential toxicity. Thus, current research aims to overcome safety concerns while maximizing their potential.

Supramolecular gels - a panorama of low-molecular-weight gelators from ancient origins to next-generation technologies

Supramolecular gels, self-assembled from low-molecular-weight gelators (LMWGs), have a long history and a bright future. This review provides an overview of these materials, from their use in lubrication and personal care in the ancient world, through to next-generation technologies. In academic terms, colloid scientists in the 19th and early 20th centuries first understood such gels as being physically assembled as a result of weak interactions, combining a solid-like network having a degree of crystalline order with a highly mobile liquid-like phase. During the 20th century, industrial scientists began using these materials in new applications in the polymer, oil and food industries. The advent of supramolecular chemistry in the late 20th century, with its focus on non-covalent interactions and controlled self-assembly, saw the horizons for these materials shifted significantly beyond their historic rheological applications, expanding their potential. The ability to tune the LMWG chemical structure, manipulate hierarchical assembly, develop multi-component systems, and introduce new types of responsive and interactive behaviour, has been transformative. Furthermore, the dynamics of these materials are increasingly understood, creating metastable gels and transiently-fueled systems. New approaches to shaping and patterning gels are providing a unique opportunity for more sophisticated uses. These supramolecular advances are increasingly underpinning and informing next-generation applications - from drug delivery and regenerative medicine to environmental remediation and sustainable energy. In summary, this article presents a panorama over the field of supramolecular gels, emphasising how both academic and industrial scientists are building on the past, and engaging new fundamental insights and innovative concepts to open up exciting horizons for their future use.

Acid⋅⋅⋅Amide Supramolecular Synthon for Tuning Amino Acid-Based Hydrogels' Properties

Supramolecular hydrogels formed by the self-assembly of N-Fmoc-l-phenylalanine derivatives are gaining relevance for several applications in the materials and biomedical fields. In the challenging attempt to predict or tune their properties, we selected Fmoc-pentafluorophenylalanine (1) as a model efficient gelator, and studied its self-assembly in the presence of benzamide (2), a non-gelator able to form strong hydrogen bonds with the amino acid carboxylic group. Equimolar mixtures of 1 and 2 in organic solvents afforded a 1 : 1 co-crystal thanks to the formation of an acid⋅⋅⋅amide heterodimeric supramolecular synthon. The same synthon occurred in the transparent gels formed by mixing the two components in 1 : 1 ratio in aqueous media, as revealed by structural, spectroscopic, and thermal characterizations performed on both the co-crystal powder and the lyophilized hydrogel. These findings revealed the possibility of modulating the properties of amino acid-based hydrogels by involving the gelator in the formation of a co-crystal. Such a crystal engineering-based approach is shown also to be useful for the time-delayed release of suitable bioactive molecules, when involved as hydrogel coformers.

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.

Enzyme-Triggered l-α/d-Peptide Hydrogels as a Long-Acting Injectable Platform for Systemic Delivery of HIV/AIDS Drugs

Eradicating HIV/AIDS by 2030 is a central goal of the World Health Organization. Patient adherence to complicated dosage regimens remains a key barrier. There is a need for convenient long-acting formulations that deliver drugs over sustained periods. This paper presents an alternative platform, an injectable in situ forming hydrogel implant to deliver a model antiretroviral drug (zidovudine [AZT]) over 28 days. The formulation is a self-assembling ultrashort d or l-α peptide hydrogelator, namely phosphorylated (naphthalene-2-ly)-acetyl-diphenylalanine-lysine-tyrosine-OH (NapFFKY[p]-OH), covalently conjugated to zidovudine via an ester linkage. Rheological analysis demonstrates phosphatase enzyme instructed self-assembly, with hydrogels forming within minutes. Small angle neutron scattering data suggest hydrogels form narrow radius (≈2 nm), large length fibers closely fitting the flexible cylinder elliptical model. d-Peptides are particularly promising for long-acting delivery, displaying protease resistance for 28 days. Drug release, via hydrolysis of the ester linkage, progress under physiological conditions (37 °C, pH 7.4, H2 O). Subcutaneous administration of Napffk(AZT)Y[p]G-OH in Sprague Dawley rats demonstrate zidovudine blood plasma concentrations within the half maximal inhibitory concentration (IC50 ) range (30-130 ng mL-1 ) for 35 days. This work is a proof-of-concept for the development of a long-acting combined injectable in situ forming peptide hydrogel implant. These products are imperative given their potential impact on society.

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.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

SIGNIFICANCE

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.

Bioinks adapted for in situ bioprinting scenarios of defect sites: a review

In situ bioprinting provides a reliable solution to the problem of in vitro tissue culture and vascularization by printing tissue directly at the site of injury or defect and maturing the printed tissue using the natural cell microenvironment in vivo. As an emerging field, in situ bioprinting is based on computer-assisted scanning results of the defect site and is able to print cells directly at this site with biomaterials, bioactive factors, and other materials without the need to transfer prefabricated grafts as with traditional in vitro 3D bioprinting methods, and the resulting grafts can accurately adapt to the target defect site. However, one of the important reasons hindering the development of in situ bioprinting is the absence of suitable bioinks. In this review, we will summarize bioinks developed in recent years that can adapt to in situ printing scenarios at the defect site, considering three aspects: the in situ design strategy of bioink, the selection of commonly used biomaterials, and the application of bioprinting to different treatment scenarios.

Influence of central sidechain on self-assembly of glycine-x-glycine peptides

Low molecular weight gelators (LMWGs) are the subject of intense research for a range of biomedical and engineering applications. Peptides are a special class of LMWG, which offer infinite sequence possibilities and, therefore, engineered properties. This work examines the propensity of the GxG peptide family, where x denotes a guest residue, to self-assemble into fibril networks via changes in pH and ethanol concentration. These triggers for gelation are motivated by recent work on GHG and GAG, which unexpectedly self-assemble into centimeter long fibril networks with unique rheological properties. The propensity of GxG peptides to self-assemble, and the physical and chemical properties of the self-assembled structures are characterized by microscopy, spectroscopy, rheology, and X-ray diffraction. Interestingly, we show that the number, length, size, and morphology of the crystalline self-assembled aggregates depend significantly on the x-residue chemistry and the solution conditions, i.e. pH, temperature, peptide concentration, etc. The different x-residues allow us to probe the importance of different peptide interactions, e.g. π-π stacking, hydrogen bonding, and hydrophobicity, on the formation of fibrils. We conclude that fibril formation requires π-π stacking interactions in pure water, while hydrogen bonding can form fibrils in the presence of ethanol-water solutions. These results validate and support theoretical arguments on the propensity for self-assembly and leads to a better understanding of the relationship between peptide chemistry and fibril self-assembly. Overall, GxG peptides constitute a unique family of peptides, whose characterization will aid in advancing our understanding of self-assembly driving forces for fibril formation in peptide systems.

Advancements and Utilizations of Scaffolds in Tissue Engineering and Drug Delivery

The drug development process requires a thorough understanding of the scaffold and its three-dimensional structure. Scaffolding is a technique for tissue engineering and the formation of contemporary functioning tissues. Tissue engineering is sometimes referred to as regenerative medicine. They also ensure that drugs are delivered with precision. Information regarding scaffolding techniques, scaffolding kinds, and other relevant facts, such as 3D nanostructuring, are discussed in depth in this literature. They are specific and demonstrate localized action for a specific reason. Scaffold's acquisition nature and flexibility make it a new drug delivery technology with good availability and structural parameter management.

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.

De Novo Self-Assembling Peptides Mediate the Conversion of Temozolomide and Delivery of a Model Drug into Glioblastoma Multiforme Cells

Glioblastoma multiforme (GBM) is the most aggressive central nervous system tumor, and standard treatment, including surgical resection, radiation, and chemotherapy, has not significantly improved patient outcomes over the last 20 years. Temozolomide (TMZ), the prodrug most commonly used to treat GBM, must pass the blood–brain barrier and requires a basic pH to convert to its active form. Due to these barriers, less than 30% of orally delivered TMZ reaches the central nervous system and becomes bioactive. In this work, we have developed a novel biomaterial delivery system to convert TMZ to its active form and that shows promise for intracellular TMZ delivery. Self-assembling peptides were characterized under several different assembly conditions and evaluated for TMZ loading and conversion. Both solvent and method of assembly were found to affect the supramolecular and secondary structure of peptide assemblies. Additionally, as peptides degraded in phosphate-buffered saline, TMZ was rapidly converted to its active form. This work demonstrates that peptide-based drug delivery systems can effectively create a local stimulus during drug delivery while remaining biocompatible. This principle could be used in many future biomedical applications in addition to cancer treatment, such as wound healing and regenerative medicine.

Prolonged release of VEGF and Ang1 from intralesionally implanted hydrogel promotes perilesional vascularization and functional recovery after experimental ischemic stroke

Injectable hydrogels can generate and support pro-repair environments in injured tissue. Here we used a slow-releasing drug carrying in situ-forming hydrogel to promote post-stroke recovery in a rat model. Release kinetics were measured in vitro and in vivo with MRI, using gadolinium-labeled albumin (Galbumin), which demonstrated prolonged release over multiple weeks. Subsequently, this hydrogel was used for long-term delivery of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1) (Gel VEGF + Ang1, n = 14), in a photothrombotically induced cortical stroke lesion in rats. Control stroke animals were intralesionally injected with saline (Saline, n = 10), non-loaded gel (Gel, n = 10), or a single bolus of VEGF + Ang1 in saline (Saline VEGF + Ang1, n = 10). MRI was executed to guide hydrogel injection. Functional recovery was assessed with sensorimotor function tests, while tissue status and vascularization were monitored by serial in vivo MRI. Significant recovery from sensorimotor deficits from day 28 onwards was only measured in the Gel VEGF + Ang1 group. This was accompanied by significantly increased vascularization in the perilesional cortex. Histology confirmed (re)vascularization and neuronal sparing in perilesional areas. In conclusion, intralesional injection of in situ-forming hydrogel loaded with pro-angiogenic factors can support prolonged brain tissue regeneration and promote functional recovery in the chronic phase post-stroke.

CMC-based hydrogels loaded with Hypericum perforatum nanoemulsion for potential wound dressing applications

Wound healing is a complicated process requiring appropriate environment to accelerate healing process. In the recent years, many wound dressings have been developed for treating various kinds of wounds. In this study, we aimed to develop a novel dressing with high ability of burn wound healing and minimum side effects. Carboxymethyl cellulose (CMC) based hydrogels containing Hypericum perforatum were developed by grafting methacrylic acid and acrylamide onto CMC to produce a good mechanical strength dressing. Covalent crosslinking, which is responsible for stable mechanical structure, led to a 3D structure with appropriate water vapor transmission rate (2950 g/m2/day), controlled drug release (33% in 78 h), and great burn healing ability (almost complete healing in 10 day). The hydrogel has proper antimicrobial activity against the tested microorganisms. Zone of inhibition against E.coli was the higher in comparison with S. aureus and Candida. Minimum inhibitory concentration (MIC) for C. albicans, S. aureus, and E. coli were as 6, 4, and 5 mg/ml of H. perforatum. In vivo experiments on rats revealed that wound healing process by loaded hydrogels was faster in comparison with control group. All the results indicated that prepared hydrogel has the capability to accelerate burn wound healing process.

Controlling Doxorubicin Release from a Peptide Hydrogel through Fine-Tuning of Drug-Peptide Fiber Interactions

Hydrogels are versatile materials that have emerged in the last few decades as promising candidates for a range of applications in the biomedical field, from tissue engineering and regenerative medicine to controlled drug delivery. In the drug delivery field, in particular, they have been the subject of significant interest for the spatially and temporally controlled delivery of anticancer drugs and therapeutics. Self-assembling peptide-based hydrogels, in particular, have recently come to the fore as potential candidate vehicles for the delivery of a range of drugs. In order to explore how drug–peptide interactions influence doxorubicin (Dox) release, five β-sheet-forming self-assembling peptides with different physicochemical properties were used for the purpose of this study, namely: FEFKFEFK (F8), FKFEFKFK (FK), FEFEFKFE (FE), FEFKFEFKK (F8K), and KFEFKFEFKK (KF8K) (F: phenylalanine; E: glutamic acid; K: lysine). First, Dox-loaded hydrogels were characterized to ensure that the incorporation of the drug did not significantly affect the hydrogel properties. Subsequently, Dox diffusion out of the hydrogels was investigated using UV absorbance. The amount of drug retained in F8/FE composite hydrogels was found to be directly proportional to the amount of charge carried by the peptide fibers. When cation−π interactions were used, the position and number of end-lysine were found to play a key role in the retention of Dox. In this case, the amount of Dox retained in F8/KF8K composite hydrogels was linked to the amount of end-lysine introduced, and an end-lysine/Dox interaction stoichiometry of 3/1 was obtained. For pure FE and KF8K hydrogels, the maximum amount of Dox retained was also found to be related to the overall concentration of the hydrogels and, therefore, to the overall fiber surface area available for interaction with the drug. For 14 mM hydrogel, ∼170–200 μM Dox could be retained after 24 h. This set of peptides also showed a broad range of susceptibilities to enzymatic degradation opening the prospect of being able to control also the rate of degradation of these hydrogels. Finally, the Dox released from the hydrogel was shown to be active and affect 3T3 mouse fibroblasts viability in vitro. Our study clearly shows the potential of this peptide design as a platform for the formulation of injectable or sprayable hydrogels for controlled drug delivery.

Effects of a novel self-assembling peptide scaffold on bone regeneration and controlled release of two growth factors

RADA16 is a self-assembling peptide material with good bioactivity. To improve the bioactivity of a material, some specific functional motifs can be added to its peptide sequence. Here, we report a self-assembling peptide nanogel, RADA16-RGD, that has better bioactivity than RADA16 and can simultaneously carry and control the release of two growth factors, VEGF and BMP-2, which have synergistic effects on bone formation. The peptide materials were characterized by transmission electron microscopy and scanning electron microscopy. The mechanical properties of the peptides were evaluated by the rheology test. The biocompatibility of the materials was evaluated via the use of the CCK-8 test, live/dead staining and confocal laser scanning microscopy. Osteogenesis capability in vitro was evaluated by means of ALP staining, extracellular matrix mineralization and detection of osteogenic markers. The controlled release of growth factors was examined by ELISA. The results showed that RADA16-RGD exhibited a better ability than RADA16 to promote cell proliferation, adhesion and bone formation. In addition, RADA16-RGD had good biocompatibility and exhibited effective controlled release of VEGF and BMP-2. More importantly, compared with RADA16-RGD loaded with single growth factor or without growth factors, RADA16-RGD loaded with two growth factors exhibited a stronger ability to promote cell proliferation and osteogenesis. This study provides a promising strategy for the application of self-assembling peptides to promote osteogenesis and controlled release of proteins.

Bioinspired short peptide hydrogel for versatile encapsulation and controlled release of growth factor therapeutics

A short bioinspired octapeptide, GV8, can self-assemble under mild conditions into biodegradable supramolecular physical hydrogels with high storage modulus and good biocompatibility. GV8 hydrogels can encapsulate both single or multiple macromolecular protein-based therapeutics in a simple one-pot formulation manner, making it a promising candidate to address challenges faced by existing synthetic polymer or peptide hydrogels with complex gelation and drug-encapsulation processes. Alongside its versatility, the hydrogel exhibits concentration-dependent storage modulus and controlled drug-release action. We demonstrate that GV8 hydrogels loaded with adipose-derived mesenchymal stem cells (ADMSC) secretome remain mechanically robust, and exhibit promising potential for wound healing applications by preserving secretome activity while maintaining a constant supply of ADMSC secretome to promote epithelial cell migration. Overall, our work highlights the potential of GV8 peptide hydrogel as a versatile and safe carrier for encapsulation and delivery of macromolecular therapeutics. STATEMENT OF SIGNIFICANCE: Supramolecular peptide hydrogels are a popular choice for protein-based macromolecular therapeutics delivery; however, despite the development of abundant hydrogel systems, several challenges limit their adaptability and practical applications. GV8 short peptide hydrogel circumvents these drawbacks and demonstrates the ability to function as a versatile growth factor (GF) encapsulant. It can encapsulate precise concentrations of complex adipose-derived mesenchymal stem cells secretome mixtures with a one-pot formulation approach and perform controlled release of GFs with preserved activity without compromising the self-assembly and mechanical properties of the hydrogel's supramolecular network. The significance of GV8 hydrogel lies in its gelation simplicity and versatility to encapsulate and deliver macromolecular therapeutics, thus representing a promising biomaterial for regenerative medicine applications.

Factors Affecting Secondary and Supramolecular Structures of Self-Assembling Peptide Nanocarriers

Self-assembling peptides are a popular vector for therapeutic cargo delivery due to their versatility, tunability, and biocompatibility. Accurately predicting secondary and supramolecular structures of self-assembling peptides is essential for de novo peptide design. However, computational modeling of such assemblies is not yet able to accurately predict structure formation for many peptide sequences. This review identifies patterns in literature between secondary and supramolecular structures, primary sequences, and applications to provide a guide for informed peptide design. An overview of peptide structures, their applications as nanocarriers, and analytical methods for characterizing secondary and supramolecular structure is examined. A top-down approach is then used to identify trends between peptide sequence and assembly structure from the current literature, including an analysis of the drivers at work, such as local and nonlocal sequence effects and solution conditions.

"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.

Prevention of esophageal stricture after circumferential endoscopic submucosal dissection using a modified self-assembling peptide

Circumferential endoscopic resection (ER) of the esophageal mucosa could find its place in the treatment of dysplastic Barrett's esophagus or extensive squamous cell neoplasia. However, the occurrence of esophageal strictures remains a major complication after ER exceeding 75% of the circumference. The aim of this study was to assess the effect of a modified, pH = 2, self-assembling peptide matrix (4[Arg-Ala-Asp-Ala]) (SAP) on the development of esophageal stricture after circumferential ER in a swine model. We performed a circumferential ER in 35 swine under general anesthesia. Five animals were included in the control group, 11 animals received the SAP matrix immediately after the resection, and 11 received the SAP matrix associated to a local steroid immediately after the resection. Follow-up endoscopy and esophagogram were performed before slaughter and necropsy at day 14. Eight treated animals were kept alive until day 28. At day 14, 27% of the animals in the SAP group developed a symptomatic stricture versus 100% in the control group (P = 0.008) and 50% in the SAP-triamcinolone group (P = 0.11). Application of an SAP matrix after circumferential ER in the swine allowed a significant reduction of the incidence of symptomatic stricture at day 14. Adding triamcinolone brought no significant improvement.

Construction of a hydroxide responsive C3-symmetric supramolecular gel for controlled release of small molecules

A C3-symmetric acylhydrazone-based low molecular weight gelator (BHTP) bearing three pyridine units was synthesized and it was found to form a stable supramolecular gel in the mixture solvent of DMSO-H2O. The morphology of the gel as observed by FE-SEM showed a dense sheet structure. Hydrogen bonding and π-π stacking between the gelators were determined as the non-covalent interactions for the gelation, which were investigated thoroughly using XRD, UV-Vis, 1H NMR and FT-IR instruments. BHTP could form pH tolerant supramolecular gels in the widest range of pH values from 1 to 11. The DMSO-H2O (v : v = 1 : 1) gel exhibited selective response to OH- over a series of other anions through the color change from a white gel to a yellow solution, and the OH- response mechanism was proved by 1H NMR experiments. In solution, the lowest detection limit of BHTP for OH- was calculated to be as low as 1.62 × 10-7 M via UV-Vis titration experiments. Finally, encapsulation and controlled release of small molecules such as rhodamine B, crystal violet and methyl orange have been successfully carried out, demonstrating the potential for drug delivery application of this C3-symmetric supramolecular gel. This work opens a novel avenue for the preparation of supramolecular gel-based multiple functional smart materials.

Self-assembling peptide hydrogel SPG-178 as a pancreatic fistula-preventing agent

PURPOSE

Pancreatic fistula (PF) is a common and challenging complication after pancreatic surgery. The aim of this study was to investigate the efficacy of a new method for preventing PF utilizing self-assembling peptide hydrogel SPG-178 as a preclinical study.

METHODS

The degradability of SPG-178 was confirmed by mixing it with protease. A PF rat model was then established to investigate the efficacy of SPG-178 at preventing PF. After transecting the pancreatic duct toward the spleen, SPG-178 was attached to both sides of the pancreatic stump. The levels of amylase and lipase in both the serum and ascites were measured and surgical specimens investigated pathologically.

RESULTS

The hardness of SPG-178 did not change when treated with protease over a short period. The ascitic amylase level was significantly lower in rats treated with SPG-178 than rats who were not 3 days after transection of the pancreatic duct toward the spleen. Pathological examination showed fewer inflammatory cells and presence of a structure body on the surface of the pancreatic stump in the SPG-178-treated group. SPG-178 remained on the surface and many cells that covered it formed fibrous tissue or mesothelium.

CONCLUSION

Self-assembling peptide hydrogel SPG-178 has potential as a tool for preventing PF.

Amyloid-Like Aggregation in Diseases and Biomaterials: Osmosis of Structural Information

The discovery that the polypeptide chain has a remarkable and intrinsic propensity to form amyloid-like aggregates endowed with an extraordinary stability is one of the most relevant breakthroughs of the last decades in both protein/peptide chemistry and structural biology. This observation has fundamental implications, as the formation of these assemblies is systematically associated with the insurgence of severe neurodegenerative diseases. Although the ability of proteins to form aggregates rich in cross-β structure has been highlighted by recent studies of structural biology, the determination of the underlying atomic models has required immense efforts and inventiveness. Interestingly, the progressive molecular and structural characterization of these assemblies has opened new perspectives in apparently unrelated fields. Indeed, the self-assembling through the cross-β structure has been exploited to generate innovative biomaterials endowed with promising mechanical and spectroscopic properties. Therefore, this structural motif has become the fil rouge connecting these diversified research areas. In the present review, we report a chronological recapitulation, also performing a survey of the structural content of the Protein Data Bank, of the milestones achieved over the years in the characterization of cross-β assemblies involved in the insurgence of neurodegenerative diseases. A particular emphasis is given to the very recent successful elucidation of amyloid-like aggregates characterized by remarkable molecular and structural complexities. We also review the state of the art of the structural characterization of cross-β based biomaterials by highlighting the benefits of the osmosis of information between these two research areas. Finally, we underline the new promising perspectives that recent successful characterizations of disease-related amyloid-like assemblies can open in the biomaterial field.

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.

Electrospun Nanofibers of Natural and Synthetic Polymers as Artificial Extracellular Matrix for Tissue Engineering

Many types of polymer nanofibers have been introduced as artificial extracellular matrices. Their controllable properties, such as wettability, surface charge, transparency, elasticity, porosity and surface to volume proportion, have attracted much attention. Moreover, functionalizing polymers with other bioactive components could enable the engineering of microenvironments to host cells for regenerative medical applications. In the current brief review, we focus on the most recently cited electrospun nanofibrous polymeric scaffolds and divide them into five main categories: natural polymer-natural polymer composite, natural polymer-synthetic polymer composite, synthetic polymer-synthetic polymer composite, crosslinked polymers and reinforced polymers with inorganic materials. Then, we focus on their physiochemical, biological and mechanical features and discussed the capability and efficiency of the nanofibrous scaffolds to function as the extracellular matrix to support cellular function.

Self-Assembling Peptide-Based Hydrogels in Angiogenesis

Ischemic diseases, especially in the heart and the brain, have become a serious threat to human health. Growth factor and cell therapy are emerging as promising therapeutic strategies; however, their retention and sustainable functions in the injured tissue are limited. Self-assembling peptide (SAP)-based hydrogels, mimicking the extracellular matrix, are therefore introduced to encapsulate and controllably release cells, cell-derived exosomes or growth factors, thus promoting angiogenesis and tissue recovery after ischemia. We will summarize the classification, composition and structure of SAPs, and the influencing factors for SAP gelation. Moreover, we will describe the functionalized SAPs, and the combinatorial therapy of cells, exosomes or growth factors with functionalized SAPs for angiogenic process as well as its advantage in immunogenicity and injectability. Finally, an outlook on future directions and challenges is provided.

Advances in self-assembled injectable hydrogels for cancer therapy

Non-specific toxicity of chemotherapeutics and evolution of malignant tumors against them are major challenges for existing cancer chemotherapeutic regimens. Engineering of nanomaterials has attempted to minimize the toxicity of anticancer drugs, but systemic delivery of these nanomaterials still imposes many hurdles in their clinical use like burst release of chemotherapeutics and toxicity and immunogenicity associated with excipients of nanomaterials. However, there has been a surge in the development of natural and synthetic nanomaterials to deliver anticancer agents to the diseased (tumor) site as it can minimize the systemic circulation of anticancer drugs and reduce the toxicity-related challenges. Therefore, localized drug delivery is considered as the most effective way to deliver therapeutics but is further challenged by poor biodegradability, high immunogenicity, poor drug entrapment efficacy and inability to maintain sustained release of anticancer agents at the tumor site. This review maps out recent advancements in engineering of low molecular weight hydrogels derived from amino acid, fatty acyl, steroidal lipid and drug conjugated amphiphilic scaffolds. We have summarized the efforts for the development of molecular hydrogels in terms of biocompatibility, therapeutic potential and challenges associated with existing molecular hydrogels for cancer therapy.

Impact of C-Terminal Chemistry on Self-Assembled Morphology of Guanosine Containing Nucleopeptides

Herein, we report the design and characterization of guanosine-containing self-assembling nucleopeptides that form nanosheets and nanofibers. Through spectroscopy and microscopy analysis, we propose that the peptide component of the nucleopeptide drives the assembly into β-sheet structures with hydrogen-bonded guanosine forming additional secondary structures cooperatively within the peptide framework. Interestingly, the distinct supramolecular morphologies are driven not by metal cation responsiveness common to guanine-based materials, but by the C-terminal peptide chemistry. This work highlights the structural diversity of self-assembling nucleopeptides and will help advance the development of applications for these supramolecular guanosine-containing nucleopeptides.

Human Urinal Cell Reprogramming: Synthetic 3D Peptide Hydrogels Enhance Induced Pluripotent Stem Cell Population Homogeneity

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs), which have promising potential applications in regenerative medicine. However, the challenges of successful applications of human iPSCs for medical purposes are the low generation efficiency, heterogeneous colonies, and exposure to the animal-derived product Matrigel. We aimed to investigate whether human urinal cells could be efficiently reprogrammed into iPSCs in three-dimensional Puramatrix (3D-PM) compared to two-dimensional Matrigel (2D-MG) and to understand how this 3D hydrogel environment affects the reprogramming process. Human urinal cells were successfully reprogrammed into iPSCs in the defined synthetic animal-free 3D-PM. Interestingly, although the colony efficiency in 3D-PM was similar to that in 2D-MG (∼0.05%), the reprogrammed colonies in 3D-PM contained an iPSC population with significantly higher homogeneity, as evidenced by the pluripotent-like morphology and expression of markers. This was further confirmed by transcriptome profile analysis in bulk cells and at the single cell level. Moreover, the homogeneity of the iPSC population in 3D-PM colonies was correlated with the downregulation of integrin β1 (ITGB1) and phosphorylated focal adhesion kinase (FAK). Collectively, 3D-PM provides an alternative approach for obtaining iPSCs with enhanced homogeneity. This work also unveiled the regulation of human somatic cell reprogramming via the extracellular microenvironment.

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.

Conformation and Morphology of 4-(NH2/OH)-Substituted l/d-Prolyl Polypeptides: Effect of Homo- and Heterochiral Backbones on Formation of β-Structures and Nanofibers

The relative stereochemistry of C2 and C4 in 4-substituted prolyl polypeptides plays an important role in defining the derived conformation in solution. cis-(2S,4S)-Amino/hydroxy-l-prolyl polypeptide (lC-Amp 9/lC-Hyp 9) shows a PPII conformation in phosphate buffer and a β-structure in a relatively hydrophobic solvent, trifluoroethanol (TFE). It is now demonstrated that the homochiral enantiomeric cis-substituted d-prolyl polypeptide (dC-Amp 9/dC-Hyp 9) exhibits mirror image β-structures in TFE. In the case of alternating heterochiral prolyl peptides, it is the trans-substituted [lT(2S,4R)-dT(2R,4S)] n prolyl polypeptide that shows β-structures in TFE, while the cis-substituted [lC(2S,4S)-dC(2R,4R)] n prolyl polypeptide is disordered in both phosphate buffer and TFE. The results highlight the important chirality-specific structural requirements for β-structure formation. The observed conformation in solution (circular dichroism (CD)) is also correlated with the morphology of the self-assemblies (field emission scanning electron microscopy (FESEM)), with the PPII form leading to spherical nanoparticles and β-structures leading to nanofiber formation. The results shed light on the role of relative stereochemistry at C2 and C4 in defining the polyproline peptide conformation in solution and how different conformations drive self-assemblies of peptides toward specific nanostructures.

Electrostatic interactions regulate the release of small molecules from supramolecular hydrogels

Supramolecular hydrogels have great potential as biomaterials for sustained delivery of therapeutics. While peptide-based supramolecular hydrogels have been developed that show promise for drug delivery applications, the high cost of production has limited their widespread adoption. Low molecular weight (LMW) supramolecular hydrogels are emerging as attractive and inexpensive alternatives to peptide-based hydrogels. We recently reported novel cationic fluorenylmethyloxycarbonyl-modified phenylalanine (Fmoc-Phe) hydrogels for localized and sustained in vivo release of an anti-inflammatory agent for functional pain remediation. In an effort to further elucidate design principles to optimize these materials for delivery of a variety of molecular agents, we herein report a systematic examination of electrostatic effects on the release of cargo molecules from Fmoc-Phe derived hydrogels. Specifically, we interrogate the release of cationic, anionic, and neutral cargo molecules from a series of cationic and anionic Fmoc-Phe derived hydrogels. We observed that cargo was readily released from the hydrogels except when the cargo and hydrogel network had complementary charges, in which case the cargo was highly retained in the network. These results demonstrate that the electrostatic characteristics of both the hydrogel network and the specific cargo are critical design parameters in the formulation of LMW supramolecular hydrogel systems in the development of next-generation materials for drug delivery applications.

Supramolecular Peptide Assemblies as Antimicrobial Scaffolds

Antimicrobial discovery in the age of antibiotic resistance has demanded the prioritization of non-conventional therapies that act on new targets or employ novel mechanisms. Among these, supramolecular antimicrobial peptide assemblies have emerged as attractive therapeutic platforms, operating as both the bactericidal agent and delivery vector for combinatorial antibiotics. Leveraging their programmable inter- and intra-molecular interactions, peptides can be engineered to form higher ordered monolithic or co-assembled structures, including nano-fibers, -nets, and -tubes, where their unique bifunctionalities often emerge from the supramolecular state. Further advancements have included the formation of macroscopic hydrogels that act as bioresponsive, bactericidal materials. This systematic review covers recent advances in the development of supramolecular antimicrobial peptide technologies and discusses their potential impact on future drug discovery efforts.

Prediction of Amphiphilic Cell-Penetrating Peptide Building Blocks from Protein-Derived Amino Acid Sequences for Engineering of Drug Delivery Nanoassemblies

Amphiphilic molecules, forming self-assembled nanoarchitectures, are typically composed of hydrophobic and hydrophilic domains. Peptide amphiphiles can be designed from two, three, or four building blocks imparting novel structural and functional properties and affinities for interaction with cellular membranes or intracellular organelles. Here we present a combined numerical approach to design amphiphilic peptide scaffolds that are derived from the human nuclear K_i-67 protein. K_i-67 acts, like a biosurfactant, as a steric and electrostatic charge barrier against the collapse of mitotic chromosomes. The proposed predictive design of new K_i-67 protein-derived amphiphilic amino acid sequences exploits the computational outcomes of a set of web-accessible predictors, which are based on machine learning methods. The ensemble of such artificial intelligence algorithms, involving support vector machine (SVM), random forest (RF) classifiers, and neural networks (NN), enables the nanoengineering of a broad range of innovative peptide materials for therapeutic delivery in various applications. Amphiphilic cell-penetrating peptides (CPP), derived from natural protein sequences, may spontaneously form self-assembled nanocarriers characterized by enhanced cellular uptake. Thanks to their inherent low immunogenicity, they may enable the safe delivery of therapeutic molecules across the biological barriers.

Peptide gels for controlled release of proteins

Treatment strategies in clinics have been shifting from small molecules to protein drugs due to the promising results of a highly specific mechanism of action and reduced toxicity. Despite their prominent roles in disease treatment, delivery of the protein therapeutics is challenging due to chemical instability, immunogenicity and biological barriers. Peptide hydrogels with spatiotemporally tunable properties have shown an outstanding potential to deliver complex protein therapeutics, maintain drug efficacy and stability over time, mimicking the extracellular matrix, and responding to external stimuli. In this review, we present recent advances in peptide hydrogel design strategies, protein release kinetics and mechanisms for protein drug delivery in cellular engineering, tissue engineering, immunotherapy and disease treatments.

Directive Effect of Chain Length in Modulating Peptide Nano-assemblies

BACKGROUND

RADA-4 (Ac-RADARADARADARADA-NH2) is the most extensively studied and marketed self-assembling peptide, forming hydrogel, used to create defined threedimensional microenvironments for cell culture applications.

OBJECTIVES

In this work, we use various biophysical techniques to investigate the length dependency of RADA aggregation and assembly.

METHODS

We synthesized a series of RADA-N peptides, N ranging from 1 to 4, resulting in four peptides having 4, 8, 12, and 16 amino acids in their sequence. Through a combination of various biophysical methods including thioflavin T fluorescence assay, static right angle light scattering assay, Dynamic Light Scattering (DLS), electron microscopy, CD, and IR spectroscopy, we have examined the role of chain-length on the self-assembly of RADA peptide.

RESULTS

Our observations show that the aggregation of ionic, charge-complementary RADA motifcontaining peptides is length-dependent, with N less than 3 are not forming spontaneous selfassemblies.

CONCLUSION

The six biophysical experiments discussed in this paper validate the significance of chain-length on the epitaxial growth of RADA peptide self-assembly.

FDM-printed pH-responsive capsules for the oral delivery of a model macromolecular dye

To this day, the oral delivery of biomacromolecules remains a major developmentally-oriented challenge. A combinatorial approach was followed at this study, to formulate an efficient carrier for the in vitro delivery of a model macromolecule, fluorescein isothiocyanate-dextran 4 kDa (FD4). The model macromolecule was formulated in a self-assembling peptide hydrogel (ac-(RADA)₄-CONH₂), prior to deposition in a hydroxypropyl methylcellulose-phthalate (HPMCP)-based 3D-printed capsule. Loading of FD4 was investigated for potential alterations on the structural (AFM) and gelling properties of the peptide carrier. Thermal analysis and morphological properties of the 3D-printed capsules were assessed by TGA, DSC and microscopy studies. For the peptide hydrogel, similar release profiles of FD4 were recorded in simulated gastric fluid pH 1.2 and phosphate buffer saline pH 7.4, indicating the need for a structural barrier, to protect the peptide carrier from the acidic environment of the stomach. The pH responsive character of the HPMCP-based capsule was evidenced in the release profiles of FD4 in a sequence of release media, i.e. simulated gastric fluid pH 1.2, simulated intestinal fluid pH 6.8 and phosphate buffer saline pH 7.4. The results supported the combinatorial formulation approach as a promising system for the efficient oral delivery of biomacromolecules.

A redox-responsive organogel based on a selenium-containing low molecular mass gelator

A redox-responsive low molecular mass gelator (Chol-Se) with selenium as its redox-active center was designed and synthesized. Responsive transformation of Chol-Se in ethyl acetate between the gelation and solution was achieved.

Self-Assembling Peptides and Their Application in the Treatment of Diseases

Self-assembling peptides are biomedical materials with unique structures that are formed in response to various environmental conditions. Governed by their physicochemical characteristics, the peptides can form a variety of structures with greater reactivity than conventional non-biological materials. The structural divergence of self-assembling peptides allows for various functional possibilities; when assembled, they can be used as scaffolds for cell and tissue regeneration, and vehicles for drug delivery, conferring controlled release, stability, and targeting, and avoiding side effects of drugs. These peptides can also be used as drugs themselves. In this review, we describe the basic structure and characteristics of self-assembling peptides and the various factors that affect the formation of peptide-based structures. We also summarize the applications of self-assembling peptides in the treatment of various diseases, including cancer. Furthermore, the in-cell self-assembly of peptides, termed reverse self-assembly, is discussed as a novel paradigm for self-assembling peptide-based nanovehicles and nanomedicines.

Drug-Mimicking Nanofibrous Peptide Hydrogel for Inhibition of Inducible Nitric Oxide Synthase

In this work, we develop a drug-mimicking nanofibrous peptide hydrogel that shows long-term bioactivity comparable to a small-molecule inhibitor of inducible nitric oxide synthase (iNOS). The iNOS inhibitor, N ⁶-(1-iminoethyl)-l-lysine (l-NIL), is a positively charged amino acid whose structure could be readily integrated into the framework of a positively charged multidomain peptide (MDP) through the modification of lysine side chains. This new l-NIL-MDP maintains the self-assembling properties of the base peptide, forming β-sheet nanofibers, which entangle into a thixotropic hydrogel. The l-NIL-MDP hydrogel supports cell growth in vitro and allows syringe-directed delivery that persists in a targeted location in vivo for several weeks. Multiple characterization assays demonstrate the bioactivity of the l-NIL-MDP hydrogel to be comparable to the l-NIL small molecule. This includes iNOS inhibition of macrophages in vitro, reduced nitrotyrosine immunostaining in murine subcutaneous histology, and reduced serum levels of vascular endothelial growth factor in vivo. This study expands the toolbox of available peptide hydrogel scaffold designs that can modify biological activity without the need for any additional small-molecule drugs, proteins, or cells.

Graphene oxide: A growth factor delivery carrier to enhance chondrogenic differentiation of human mesenchymal stem cells in 3D hydrogels

Cartilage engineering with stem cells in 3D scaffolds is a promising future therapy to treat cartilage defects. One challenge in the field is to design carriers to efficaciously deliver biological factors in 3D scaffolds containing stem cells to appropriately guide differentiation of these cells in same scaffolds and promote specific tissue synthesis. Graphene-based 2D nanomaterials have recently attracted extensive interest for their biomedical applications as they can adsorb a plethora of biological molecules, thus offering high potential as delivery carriers. This study utilized graphene oxide (GO) flakes to adsorb transforming growth factor β3 (TGF-β3), which were then incorporated into a collagen hydrogel. Human mesenchymal stem cells (hMSCs) were encapsulated in the same gel and chondrogenic differentiation assessed. The study showed GO flakes adsorbed > 99% TGF-β3 with <1.7% release. Adsorbed TGF-β3 retained a similar conformation to its dissolved counterpart (free protein) but importantly demonstrated greater conformational stability. Smad2 phosphorylation was promoted, and higher chondrogenic gene expression and cartilage-specific extracellular matrix deposition were achieved compared to exogenously delivering TGF-β3 in culture media. Effects were sustained in long-term 28-day culture. The results demonstrate GO flakes as highly-efficient for delivering GFs in 3D to guide cells in the same scaffold and induce tissue formation. The ability of GO flakes to provide sustained local delivery makes this material attractive for tissue engineering strategies, in particular for regionally-specific MSC differentiation (e.g. osteochondral tissue engineering). STATEMENT OF SIGNIFICANCE: Cartilage engineering involving stem cells in 3D scaffolds is a promising future therapy to treat cartilage defects which can lead to debilitating conditions such as osteoarthritis. However, this field faces the challenge to design delivery carriers to efficaciously deliver biological factors inside these 3D cell-containing scaffolds for appropriately-guided cell differentiation. Graphene-based 2D nanomaterials offer high potential as delivery carriers, but to date studies using them to deliver biological factors have been restricted to 2D substrates, non-scaffold cell masses, or acellular 3D scaffolds. Our study for the first time demonstrated simultaneously incorporating both human mesenchymal stem cells (hMSCs) and GO (graphene oxide)-adsorbed growth factor TGFβ3 into a 3D scaffold, where GO-adsorbed TGFβ3 enhanced chondrogenic differentiation of hMSCs and cartilage-tissue synthesis throughout the scaffold without needing to repeatedly supply TGFβ3 exogenously.

Acellular and cellular approaches to improve diabetic wound healing

Chronic diabetic wounds represent a huge socioeconomic burden for both affected individuals and the entire healthcare system. Although the number of available treatment options as well as our understanding of wound healing mechanisms associated with diabetes has vastly improved over the past decades, there still remains a great need for additional therapeutic options. Tissue engineering and regenerative medicine approaches provide great advantages over conventional treatment options, which are mainly aimed at wound closure rather than addressing the underlying pathophysiology of diabetic wounds. Recent advances in biomaterials and stem cell research presented in this review provide novel ways to tackle different molecular and cellular culprits responsible for chronic and nonhealing wounds by delivering therapeutic agents in direct or indirect ways. Careful integration of different approaches presented in the current article could lead to the development of new therapeutic platforms that can address multiple pathophysiologic abnormalities and facilitate wound healing in patients with diabetes.

Sustained Release of Dexamethasone from Sulfobutyl Ether β-cyclodextrin Modified Self-Assembling Peptide Nanoscaffolds in a Perinatal Rat Model of Hypoxia-Ischemia

Inflammation plays a critical role in the development of hypoxia-ischemia (HI) induced newborn brain damage. A localized, sustained delivery of dexamethasone (Dex) through an intracerebral injection could reduce the inflammatory response in the injured perinatal brain while avoiding unnecessary side effects. Herein, investigated using anionic sulfobutyl ether β-cyclodextrin (SBE-β-CD) to load Dex in the (RADA)₄ nanofiber networks as a means of reducing the inflammatory response to HI injury is investigated. The ionic interaction between SBE-β-CD and (RADA)₄ dramatically affects nanofiber formation and the stability of the nanoscaffold is highly dependent on the SBE-β-CD/(RADA)₄ ratio. It is observed that the Dex release rate is affected by the concentration of SBE-β-CD and (RADA)₄ peptide. A higher concentration of SBE-β-CD or (RADA)₄ results in a higher drug encapsulation efficiency and slower release rate of Dex. This phenomenon may be related to the structure of fiber bundles. Animal studies show that nanoscaffold loaded with Dex inhibits both microglia activation and glial scar formation compared to controls (Dex alone or nanoscaffold alone) within 2 days of injury. It is thought that this is a step toward building a multifaceted nanoscaffold that can be used to treat HI events in perinates.

Gels of Amyloid Fibers

Protein self-assembly and formation of amyloid fibers is an early event of numerous human diseases. Continuous aggregation of amyloid fibers in vitro produces biogels, which led us to suspect that amyloid plaques and neurofibrillary tangles in Alzheimer’s disease are of biogels in nature. We applied atomic force microscopy, size exclusion chromatography, and differential scanning calorimetry to elucidate the gel’s structure, kinetics of gel formation, and melting point. We found that (1) lysozyme gelation occurs when the protein concentration is above 5 mg/mL; (2) nonfibrous protein concentration decreases and plateaus after three days of gel synthesis reaction; (3) colloidal lysozyme aggregates are detectable by both atomic force microscopy (AFM) and fast protein liquid chromatography (FPLC); (4) the gels are a three-dimensional (3D) network crosslinked by fibers coiling around each other; (5) the gels have a high melting point at around around 110 °C, which is weakly dependent on protein concentration; (6) the gels are conductive under an electric field, and (7) they form faster in the presence than in the absence of salt in the reaction buffer. The potential role of the gels formed by amyloid fibers in amyloidosis, particularly in Alzheimer’s disease was thoroughly discussed, as gels with increased viscosity, are known to restrict bulk flow and then circulation of ions and molecules.