Development of a Novel Covalently Bonded Conjugate of Caprylic Acid Tripeptide (Isoleucine-Leucine-Aspartic Acid) for Wound-Compatible and Injectable Hydrogel to Accelerate Healing

Third-degree burn injuries pose a significant health threat. Safer, easier-to-use, and more effective techniques are urgently needed for their treatment. We hypothesized that covalently bonded conjugates of fatty acids and tripeptides can form wound-compatible hydrogels that can accelerate healing. We first designed conjugated structures as fatty acid-aminoacid1-amonoacid2-aspartate amphiphiles (Cn acid-AA1-AA2-D), which were potentially capable of self-assembling into hydrogels according to the structure and properties of each moiety. We then generated 14 novel conjugates based on this design by using two Fmoc/tBu solid-phase peptide synthesis techniques; we verified their structures and purities through liquid chromatography with tandem mass spectrometry and nuclear magnetic resonance spectroscopy. Of them, 13 conjugates formed hydrogels at low concentrations (≥0.25% w/v), but C8 acid-ILD-NH2 showed the best hydrogelation and was investigated further. Scanning electron microscopy revealed that C8 acid-ILD-NH2 formed fibrous network structures and rapidly formed hydrogels that were stable in phosphate-buffered saline (pH 2-8, 37 °C), a typical pathophysiological condition. Injection and rheological studies revealed that the hydrogels manifested important wound treatment properties, including injectability, shear thinning, rapid re-gelation, and wound-compatible mechanics (e.g., moduli G″ and G', ~0.5-15 kPa). The C8 acid-ILD-NH2(2) hydrogel markedly accelerated the healing of third-degree burn wounds on C57BL/6J mice. Taken together, our findings demonstrated the potential of the Cn fatty acid-AA1-AA2-D molecular template to form hydrogels capable of promoting the wound healing of third-degree burns.

Designer peptides as versatile building blocks for functional materials

Peptides and pseudopeptides show distinct self-assembled nanostructures such as fibers, nanotubes, vesicles, micelles, toroids, helices and rods. The formation of such molecular communities through the collective behavior of molecules is not fully understood at a molecular level. All these self-assembled nanostructured materials have a wide range of applications such as drug delivery, gene delivery, biosensing, bioimaging, catalysis, tissue engineering, nano-electronics and sensing. Self-assembly is one of the most efficient and a simple strategy to generate complex functional materials. Owing to its significance, the last few decades witnessed a remarkable advancement in the field of self-assembling peptides with a plethora of new designer synthetic systems being discovered. These systems range from amphiphilic, cyclic, linear and polymeric peptides. This article presents only selected examples of such self-assembling peptides and pseudopeptides.

Synthesis and Organization of Gold-Peptide Nanoparticles for Catalytic Activities

A significant development in the synthesis strategies of metal-peptide composites and their applications in biomedical and bio-catalysis has been reported. However, the random aggregation of gold nanoparticles provides the opportunity to find alternative fabrication strategies of gold-peptide composite nanomaterials. In this study, we used a facile strategy to synthesize the gold nanoparticles via a green and simple approach where they show self-alignment on the assembled nanofibers of ultrashort oligopeptides as a composite material. A photochemical reduction method is used, which does not require any external chemical reagents for the reduction of gold ions, and resultantly makes the gold nanoparticles of size ca. 5 nm under mild UV light exposure. The specific arrangement of gold nanoparticles on the peptide nanofibers may indicate the electrostatic interactions of two components and the interactions with the amino group of the peptide building block. Furthermore, the gold-peptide nanoparticle composites show the ability as a catalyst to degradation of environmental pollutant p-nitrophenol to p-aminophenol, and the reaction rate constant for catalysis is calculated as 0.057 min-1 at a 50-fold dilute sample of 2 mg/mL and 0.72 mM gold concentration in the composites. This colloidal strategy would help researchers to fabricate the metalized bioorganic composites for various biomedical and bio-catalysis applications.

Green Synthesis of Silver-Peptide Nanoparticles Generated by the Photoionization Process for Anti-Biofilm Application

An alarming increase in antibiotic-resistant bacterial strains is driving clinical demand for new antibacterial agents. One of the oldest antimicrobial agents is elementary silver (Ag), which has been used for thousands of years. Even today, elementary Ag is used for medical purposes such as treating burns, wounds, and microbial infections. In consideration of the effectiveness of elementary Ag, the present researchers generated effective antibacterial/antibiofilm agents by combining elementary Ag with biocompatible ultrashort peptide compounds. The innovative antibacterial agents comprised a hybrid peptide bound to Ag nanoparticles (IVFK/Ag NPs). These were generated by photoionizing a biocompatible ultrashort peptide, thus reducing Ag ions to form Ag NPs with a diameter of 6 nm. The IVFK/Ag NPs demonstrated promising antibacterial/antibiofilm activity against reference Gram-positive and Gram-negative bacteria compared with commercial Ag NPs. Through morphological changes in Escherichia coli and Staphylococcus aureus, we proposed that the mechanism of action for IVFK/Ag NPs derives from their ability to disrupt bacterial membranes. In terms of safety, the IVFK/Ag NPs demonstrated biocompatibility in the presence of human dermal fibroblast cells, and concentrations within the minimal inhibitory concentration had no significant effect on cell viability. These results demonstrated that hybrid peptide/Ag NPs hold promise as a biocompatible material with strong antibacterial/antibiofilm properties, allowing them to be applied across a wide range of applications in tissue engineering and regenerative medicine.

Supramolecular peptide nano-assemblies for cancer diagnosis and therapy: from molecular design to material synthesis and function-specific applications

Peptide molecule has high bioactivity, good biocompatibility, and excellent biodegradability. In addition, it has adjustable amino acid structure and sequence, which can be flexible designed and tailored to form supramolecular nano-assemblies with specific biomimicking, recognition, and targeting properties via molecular self-assembly. These unique properties of peptide nano-assemblies made it possible for utilizing them for biomedical and tissue engineering applications. In this review, we summarize recent progress on the motif design, self-assembly synthesis, and functional tailoring of peptide nano-assemblies for both cancer diagnosis and therapy. For this aim, firstly we demonstrate the methodologies on the synthesis of various functional pure and hybrid peptide nano-assemblies, by which the structural and functional tailoring of peptide nano-assemblies are introduced and discussed in detail. Secondly, we present the applications of peptide nano-assemblies for cancer diagnosis applications, including optical and magnetic imaging as well as biosensing of cancer cells. Thirdly, the design of peptide nano-assemblies for enzyme-mediated killing, chemo-therapy, photothermal therapy, and multi-therapy of cancer cells are introduced. Finally, the challenges and perspectives in this promising topic are discussed. This work will be useful for readers to understand the methodologies on peptide design and functional tailoring for highly effective, specific, and targeted diagnosis and therapy of cancers, and at the same time it will promote the development of cancer diagnosis and therapy by linking those knowledges in biological science, nanotechnology, biomedicine, tissue engineering, and analytical science.

Synergistic Antitumor Efficacy Mediated by Liposomal Co-Delivery of Polymeric Micelles of Vinorelbine and Cisplatin in Non-Small Cell Lung Cancer

PURPOSE

Non-small cell lung cancer (NSCLC) is an aggressive tumor with high mortality and poor prognosis. In this study, we designed a liposome encapsulating polymeric micelles (PMs) loaded with vinorelbine (NVB) and cis-diamminedichloroplatinum (II) (cisplatin or CDDP) for the treatment of NSCLC.

MATERIALS AND METHODS

Sodium poly(α-l-glutamic acid)-graft-methoxy-polyethylene glycol (PLG-G-PEG5K) was used to prepare NVB-loaded NVB-PMs and CDDP-loaded CDDP-PMs that were co-encapsulated into liposomes by a reverse evaporation method, yielding NVB and CDDP co-delivery liposomes (CoNP-lips) composed of egg phosphatidyl lipid-80/cholesterol/DPPG/DSPE-mPEG2000 at a molar ratio of 52:32:14:2. The CoNP-lips were characterized in terms of particle size, zeta potential, drug content, encapsulation efficiency, and structural properties. Drug release by the CoNP-lips as well as their stability and cytotoxicity was evaluated in vitro, and their antitumor efficacy was assessed in a mouse xenograft model of Lewis lung carcinoma cell-derived tumors.

RESULTS

CoNP-lips had a spherical shape with uniform size distribution; the average particle size was 162.97±9.06 nm, and the average zeta potential was -13.02±0.22 mV. In vitro cytotoxicity analysis and the combination index demonstrated that the CoNP-lips achieved a synergistic cytotoxic effect at an NVB:CDDP weight ratio of 2:1 in an NSCLC cell line. There was sustained release of both drugs from CoNP-lips. The pharmacokinetic analysis showed that CoNP-lips had a higher plasma half-life than NP solution, with 6.52- and 8.03-fold larger areas under the receiver operating characteristic curves of NVB and CDDP. CoNP-lips showed antitumor efficacy in tumor-bearing C57BL/6 mice and drug accumulation in tumors via the enhanced permeability and retention effect.

CONCLUSION

CoNP-lips are a promising formulation for targeted therapy in NSCLC.

Recent Advances in Nanotechnology-Based Diagnosis and Treatments of Human Osteosarcoma

Osteosarcoma (OSA) is a type of bone cancer that begins in the cells that form bones.OSA is a rare mesenchymal bone neoplasm derived from mesenchymal stem cells. Genome disorganization, chromosomal modifications, deregulation of tumor suppressor genes, and DNA repair defects are the factors most responsible for OSA development. Despite significant advances in the diagnosing and treatment of OSA, patients' overall survival has not improved within the last twenty years. Lately, advances in modern nanotechnology have spurred development in OSA management and offered several advantages to overcome the drawbacks of conventional therapies. This technology has allowed the practical design of nanoscale devices combined with numerous functional molecules, including tumor-specific ligands, antibodies, anti-cancer drugs, and imaging probes. Thanks to their small sizes, desirable drug encapsulation efficiency, and good bioavailability, functionalized nanomaterials have found wide-spread applications for combating OSA progression. This review invokes the possible utility of engineered nanomaterials in OSA diagnosis and treatment, motivating the researchers to seek new strategies for tackling the challenges associated with it.

Supramolecular Biopolymers for Tissue Engineering

Supramolecular biopolymers (SBPs) are those polymeric units derived from macromolecules that can assemble with each other by noncovalent interactions. Macromolecular structures are commonly found in living systems such as proteins, DNA/RNA, and polysaccharides. Bioorganic chemistry allows the generation of sequence-specific supramolecular units like SBPs that can be tailored for novel applications in tissue engineering (TE). SBPs hold advantages over other conventional polymers previously used for TE; these materials can be easily functionalized; they are self-healing, biodegradable, stimuli-responsive, and nonimmunogenic. These characteristics are vital for the further development of current trends in TE, such as the use of pluripotent cells for organoid generation, cell-free scaffolds for tissue regeneration, patient-derived organ models, and controlled delivery systems of small molecules. In this review, we will analyse the 3 subtypes of SBPs: peptide-, nucleic acid-, and oligosaccharide-derived. Then, we will discuss the role that SBPs will be playing in TE as dynamic scaffolds, therapeutic scaffolds, and bioinks. Finally, we will describe possible outlooks of SBPs for TE.

Engineered Microgels-Their Manufacturing and Biomedical Applications

Microgels are hydrogel particles with diameters in the micrometer scale that can be fabricated in different shapes and sizes. Microgels are increasingly used for biomedical applications and for biofabrication due to their interesting features, such as injectability, modularity, porosity and tunability in respect to size, shape and mechanical properties. Fabrication methods of microgels are divided into two categories, following a top-down or bottom-up approach. Each approach has its own advantages and disadvantages and requires certain sets of materials and equipments. In this review, we discuss fabrication methods of both top-down and bottom-up approaches and point to their advantages as well as their limitations, with more focus on the bottom-up approaches. In addition, the use of microgels for a variety of biomedical applications will be discussed, including microgels for the delivery of therapeutic agents and microgels as cell carriers for the fabrication of 3D bioprinted cell-laden constructs. Microgels made from well-defined synthetic materials with a focus on rationally designed ultrashort peptides are also discussed, because they have been demonstrated to serve as an attractive alternative to much less defined naturally derived materials. Here, we will emphasize the potential and properties of ultrashort self-assembling peptides related to microgels.

Amyloid-Like Peptide Aggregates

Self-assembly of proteins and peptides into the amyloid fold is a widespread phenomenon in the natural world. The structural hallmark of self-assembly into amyloid fibrillar assemblies is the cross-beta motif, which conveys distinct morphological and mechanical properties. The amyloid fibril formation has contrasting results depending on the organism, in the sense that it can bestow an organism with the advantages of mechanical strength and improved functionality or, on the contrary, could give rise to pathological states. In this chapter we review the existing information on amyloid-like peptide aggregates, which could either be derived from protein sequences, but also could be rationally or de novo designed in order to self-assemble into amyloid fibrils under physiological conditions. Moreover, the development of self-assembled fibrillar biomaterials that are tailored for the desired properties towards applications in biomedical or environmental areas is extensively analyzed. We also review computational studies predicting the amyloid propensity of the natural amino acid sequences and the structure of amyloids, as well as designing novel functional amyloid materials.

A pH-Sensitive Prodrug Nanocarrier Based on Diosgenin for Doxorubicin Delivery to Efficiently Inhibit Tumor Metastasis

BACKGROUND

The metastasis, one of the biggest barriers in cancer therapy, is the leading cause of tumor deterioration and recurrence. The anti.-metastasis has been considered as a feasible strategy for clinical cancer management. It is well known that diosgenin could inhibit tumor metastasis and doxorubicin (DOX) could induce tumor apoptosis. However, their efficient delivery remains challenging.

PURPOSE

To address these issues, a novel pH-sensitive polymer-prodrug based on diosgenin nanoparticles (NPs) platform was developed to enhance the efficiency of DOX delivery (DOX/NPs) for synergistic therapy of cutaneous melanoma, the most lethal form of skin cancer with high malignancy, early metastasis and high mortality.

METHODS AND RESULTS

The inhibitory effect of DOX/NPs on tumor proliferation and migration was superior to that of NPs or free DOX. What is more, DOX/NPs could combine mitochondria-associated metastasis and apoptosis with unique internalization pathway of carrier to fight tumors. In addition, biodistribution experiments proved that DOX/NPs could efficiently accumulate in tumor sites through enhancing permeation and retention (EPR) effect compared with free DOX. Importantly, the data from in vivo experiment revealed that DOX/NPs without heart toxicity significantly inhibited tumor metastasis by exerting synergistic therapeutic effect, and reduced tumor volume and weight by inducing apoptosis.

CONCLUSION

The nanocarrier DOX/NPs with satisfying pharmaceutical characteristics based on the establishment of two different functional agents is a promising strategy for synergistically enhancing effects of cancer therapy.

Ultrashort Peptide Theranostic Nanoparticles by Microfluidic-Assisted Rapid Solvent Exchange

Ultrashort peptides (USPs), composed of three to seven amino acids, can self-assemble into nanofibers in pure water. Here, using hydrodynamic focusing and a solvent exchange method on a microfluidic setup, we convert these nanofibers into globular nanoparticles with excellent dimensional control and polydispersity. Thanks to USP nanocarriers' structure, different drugs can be loaded. We used Curcumin as a model drug to evaluate the performance of USP nanocarriers as a novel drug delivery vehicle. These nanoparticles can efficiently cross the cell membrane and possess nonlinear optical properties. Therefore, we envisage USP nanoparticles as promising future theranostic nanocarriers.

Beyond Fmoc: a review of aromatic peptide capping groups

Self-assembling short peptides have attracted widespread interest due to their tuneable, biocompatible nature and have potential applications in energy materials, tissue engineering, sensing and drug delivery. The hierarchical self-assembly of these peptides is highly dependent on the selection of not only amino acid sequence, but also the capping group which is often employed at the N-terminus of the peptide to drive self-assembly. Although the Fmoc (9H-fluorenylmethyloxycarbonyl) group is commonly used due to its utility in solid phase peptide synthesis, many other aromatic capping groups have been reported which yield functional, responsive materials. This review explores recent developments in the utilisation of functional, aromatic capping groups beyond the Fmoc group for the creation of redox-responsive, fluorescent and drug delivering hydrogel scaffolds.

The Ultrashort Peptide OW: A New Antibiotic Adjuvant

BACKGROUND

The over use of current antibiotics and low discovery rate of the new ones are leading to rapid development of multidrug-resistant pathogens worldwide. Antimicrobial peptides have shown promising results against multidrug-resistant bacteria.

OBJECTIVE

To investigate the antimicrobial activity of a new ultrashort hexapeptide (OW).

METHODS

The OW hexapeptide was designed and tested against different strains of bacteria with different levels of sensitivity. Bacterial susceptibility assays were performed according to the guidelines of the Clinical and Laboratory Institute (CLSI). The synergistic studies were then conducted using the Checkerboard assay. This was followed by checking the hemolytic effect of the hexapeptide against human blood cells and Human Embryonic Kidney cell line (HEK293). Finally, the antibiofilm activities of the hexapeptide were studied using the Biofilm Calgary method.

RESULTS

Synergistic assays showed that OW has synergistic effects with antibiotics of different mechanisms of action. It showed an outstanding synergism with Rifampicin against methicillin resistant Staphylococcus aureus; ΣFIC value was 0.37, and the MIC value of Rifampicin was decreased by 85%. OW peptide also displayed an excellent synergism with Ampicillin against multidrug-resistant Pseudomonas aeruginosa, with ΣFIC value of less than 0.38 and a reduction of more than 96% in the MIC value of Ampicillin.

CONCLUSION

This study introduced a new ultrashort peptide (OW) with promising antimicrobial potential in the management of drug-resistant infectious diseases as a single agent or in combination with commonly used antibiotics. Further studies are needed to investigate the exact mechanism of action of these peptides.

Advancement of Peptide Nanobiotechnology via Emerging Microfluidic Technology

Peptide nanotechnology has experienced a long and enduring development since its inception. Many different applications have been conceptualized, which depends on the functional groups present on the peptide and the physical shape/size of the peptide nanostructures. One of the most prominent nanostructures formed by peptides are nanoparticles. Until recently, however, it has been challenging to engineer peptide nanoparticles with low dispersity. An emerging and promising technique involves the utility of microfluidics to produce a solution of peptide nanoparticles with narrow dispersity. In this process, two or more streams of liquid are focused together to create conditions that are conducive towards the formation of narrowly dispersed samples of peptide nanoparticles. This makes it possible to harness peptide nanoparticles for the myriad of applications that are dependent on nanoparticle size and uniformity. In this focus review, we aim to show how microfluidics may be utilized to (1) study peptide self-assembly, which is critical to controlling nanostructure shape and size, and peptide-interface interactions, and (2) generate self-assembling peptide-based microgels for miniaturized cell cultures. These examples will illustrate how the emerging microfluidic approach promises to revolutionize the production and application of peptide nanoparticles in ever more diverse fields than before.

Thin peptide hydrogel membranes suitable as scaffolds for engineering layered biostructures

A short tetramer peptide, Ac-IVKC, spontaneously formed a hydrogel in water. Disulfide bonds were introduced via hydrogen peroxide (H₂O₂)-assisted oxidation, resulting in (Ac-IVKC)₂ dimers. The extent of disulfide bond formation and gel stiffness increased with the amount of H₂O₂ used and 100% dimerization was achieved with 0.2% H₂O₂. The resultant gel achieved an elastic modulus of ∼0.9 MPa, which to our knowledge, has not been reported for peptide-based hydrogels. The enhanced mechanical property enabled the fabrication of thin and transparent membranes. The hydrogel could also be handled with forceps at mm thickness, greatly increasing its ease of physical manipulation. Excess H₂O₂ was removed and the membrane was then infused with cell culture media. Various cells, including primary human corneal stromal and epithelial cells, were seeded onto the hydrogel membrane and demonstrated to remain viable. Depending on the intended application, specific cell combination or membrane stacking order could be used to engineer layered biostructures. STATEMENT OF SIGNIFICANCE: A short tetramer peptide - Ac-IVKC - spontaneously formed a hydrogel in water and disulfide bonds were introduced via hydrogen peroxide (H₂O₂)-assisted oxidation. The extent of disulfide-bond formation and gel stiffness were modulated by the amount of H₂O₂. At maximum disulfide-bond formation, the hydrogel achieved an elastic modulus of ∼0.9 MPa, which to our knowledge, has not been reported for peptide-based hydrogels. The enhanced mechanical property enabled the fabrication of thin transparent membranes that can be physically manipulated at mm thickness. The gels also supported 3D cell growth, including primary human corneal stromal and epithelial cells. Depending on the intended application, specific combination of cells or individual membrane stacking order could be used to engineer layered biostructures.

Ultrashort peptides: minimum number in amino acid residues, maximum number in bioapplications

Ultra-short peptides are an intrigue new type of biomaterials for various bioapplications. Over the decades, peptides have evolved as biomaterials due to the ease of synthesis, ease of scaling up, feasibility to be functionalized/modified, and recognition by biological system1. Peptide-based hydrogels are widely used as scaffolds for encapsulation and delivery of drugs, genes and cells. They are made of natural amino acids. Thus they are non-immunogenic. They contain carboxylic and amine groups. Thus they can be easily functionalized with bioactive moieties. However, for peptides with more than 16 amino acid residues, they are expensive due to the high synthesis cost. As such, ultra-short peptides with only 2 to 7 amino acid residues stand out due to their easy and cost-effective synthesis, facile assembly in aqueous solution, biocompatibility and mechanical stability. These ultrashort peptides can form hydrogels without the addition of enzymes or other types of cross-linkers.

A novel drug–drug nanohybrid for the self-delivery of porphyrin and cis-platinum

The thriving development of nanotechnology has greatly promoted the development of drug delivery systems (DDSs) in the past decades. However, most DDSs themselves cannot serve as diagnostic reagents and must be metabolized, by which they may become poisonous and even cause immune reactions. In this study, a novel self-delivery drug–drug system (SDDS) nanohybrid based on the coordination assembly of a photodynamic reagent, tetra-(4-carboxyphenyl)porphyrin (TCPP), and a chemotherapy reagent, cis-platinum, was designed and synthesized. The four carboxyl groups of TCPP can compete with the chloride ions of cis-platinum by coordination interactions, forming a TCPP-cis-platinum nanohybrid (PCNH) for the purpose of photodynamic/chemotherapeutic synergistic treatment with a combinational index of 0.28. Meanwhile, the PCNH system can effectively protect the photosensitizer TCPP from photobleaching when irradiated continuously in the photodynamic therapy (PDT) process, which is very crucial for PDT. Furthermore, introduction of the heavy atom platinum can greatly enhance the producing efficiency of ¹O₂ by 46%. In addition, the red emission fluorescence of TCPP is beneficial for monitoring and tracing the process of drug delivery when used in vitro. This work may pave a new way for the design of new integrated nanohybrids for diagnosis and synergistic treatment.

A novel self-delivery drug–drug system nanohybrid constructed by the coordination assembly of porphyrin and cis-platinum was used for synergetic photodynamic therapy and chemotherapy.

NIR light-responsive short peptide/2D NbSe2 nanosheets composite hydrogel with controlled-release capacity

The design of light-responsive peptide hydrogels with controllable drug release characteristics is still a challenge.

C-Terminal Residue of Ultrashort Peptides Impacts on Molecular Self-Assembly, Hydrogelation, and Interaction with Small-Molecule Drugs

Single molecular changes on a tripeptide can have dramatic effects on their self-assembly and hydrogelation. Herein, we explore C-terminal residue variation on two consistent ultrashort peptide backbones, i.e. acetylated-Leu-Ile-Val-Ala-Gly-Xaa and acetylated-Ile-Val-Xaa (Xaa = His, Arg, Asn). The objective of this study is to identify candidates that can form hydrogels for small-molecule drug (SMD) delivery. Haemolysis and cytotoxicity (with human adipose-derived mesenchymal stem cells) assays showed that the new soluble peptides (Xaa = His, Arg) are cytocompatible. Gelation studies showed that all but acetylated-Ile-Val-Arg could gel under physiological conditions. Longer peptidic backbones drive self-assembly more effectively as reflected in field emission scanning electron microscopy (FESEM) and circular dichroism spectroscopy studies. Rheological studies revealed that the resultant hydrogels have varying stiffness and yield stress, depending on the backbone and C-terminal residue. Visible spectroscopy-based elution studies with SMDs (naltrexone, methotrexate, doxorubicin) showed that besides the C-terminal residue, the shape of the SMD also determines the rate and extent of SMD elution. Based on the elution assays, infrared spectroscopy, and FESEM, we propose models for the peptide fibril-SMD interaction. Our findings highlight the importance of matching the molecular properties of the self-assembling peptide and SMD in order to achieve the desired SMD release profile.

A Review on Recent Advances in Stabilizing Peptides/Proteins upon Fabrication in Hydrogels from Biodegradable Polymers

Hydrogels evolved as an outstanding carrier material for local and controlled drug delivery that tend to overcome the shortcomings of old conventional dosage forms for small drugs (NSAIDS) and large peptides and proteins. The aqueous swellable and crosslinked polymeric network structure of hydrogels is composed of various natural, synthetic and semisynthetic biodegradable polymers. Hydrogels have remarkable properties of functionality, reversibility, sterilizability, and biocompatibility. All these dynamic properties of hydrogels have increased the interest in their use as a carrier for peptides and proteins to be released slowly in a sustained manner. Peptide and proteins are remarkable therapeutic agents in today's world that allow the treatment of severe, chronic and life-threatening diseases, such as diabetes, rheumatoid arthritis, hepatitis. Despite few limitations, hydrogels provide fine tuning of proteins and peptides delivery with enormous impact in clinical medicine. Novels drug delivery systems composed of smart peptides and molecules have the ability to drive self-assembly and form hydrogels at physiological pH. These hydrogels are significantly important for biological and medical fields. The primary objective of this article is to review current issues concerned with the therapeutic peptides and proteins and impact of remarkable properties of hydrogels on these therapeutic agents. Different routes for pharmaceutical peptides and proteins and superiority over other drugs candidates are presented. Recent advances based on various approaches like self-assembly of peptides and small molecules to form novel hydrogels are also discussed. The article will also review the literature concerning the classification of hydrogels on a different basis, polymers used, "release mechanisms" their physical and chemical characteristics and diverse applications.

Systematic Moiety Variations of Ultrashort Peptides Produce Profound Effects on Self-Assembly, Nanostructure Formation, Hydrogelation, and Phase Transition

Self-assembly of small biomolecules is a prevalent phenomenon that is increasingly being recognised to hold the key to building complex structures from simple monomeric units. Small peptides, in particular ultrashort peptides containing up to seven amino acids, for which our laboratory has found many biomedical applications, exhibit immense potential in this regard. For next-generation applications, more intricate control is required over the self-assembly processes. We seek to find out how subtle moiety variation of peptides can affect self-assembly and nanostructure formation. To this end, we have selected a library of 54 tripeptides, derived from systematic moiety variations from seven tripeptides. Our study reveals that subtle structural changes in the tripeptides can exert profound effects on self-assembly, nanostructure formation, hydrogelation, and even phase transition of peptide nanostructures. By comparing the X-ray crystal structures of two tripeptides, acetylated leucine-leucine-glutamic acid (Ac-LLE) and acetylated tyrosine-leucine-aspartic acid (Ac-YLD), we obtained valuable insights into the structural factors that can influence the formation of supramolecular peptide structures. We believe that our results have major implications on the understanding of the factors that affect peptide self-assembly. In addition, our findings can potentially assist current computational efforts to predict and design self-assembling peptide systems for diverse biomedical applications.

Supramolecular biofunctional materials

This review discusses supramolecular biofunctional materials, a novel class of biomaterials formed by small molecules that are held together via noncovalent interactions. The complexity of biology and relevant biomedical problems not only inspire, but also demand effective molecular design for functional materials. Supramolecular biofunctional materials offer (almost) unlimited possibilities and opportunities to address challenging biomedical problems. Rational molecular design of supramolecular biofunctional materials exploit powerful and versatile noncovalent interactions, which offer many advantages, such as responsiveness, reversibility, tunability, biomimicry, modularity, predictability, and, most importantly, adaptiveness. In this review, besides elaborating on the merits of supramolecular biofunctional materials (mainly in the form of hydrogels and/or nanoscale assemblies) resulting from noncovalent interactions, we also discuss the advantages of small peptides as a prevalent molecular platform to generate a wide range of supramolecular biofunctional materials for the applications in drug delivery, tissue engineering, immunology, cancer therapy, fluorescent imaging, and stem cell regulation. This review aims to provide a brief synopsis of recent achievements at the intersection of supramolecular chemistry and biomedical science in hope of contributing to the multidisciplinary research on supramolecular biofunctional materials for a wide range of applications. We envision that supramolecular biofunctional materials will contribute to the development of new therapies that will ultimately lead to a paradigm shift for developing next generation biomaterials for medicine.

Supramolecular Gels by Design: Towards the Development of Topical Gels for Self-Delivery Application

Following a supramolecular synthon approach, simple salt formation has been employed to gain access to a series of supramolecular gelators derived from the well-known non-steroidal anti-inflammatory drug (NSAID) ibuprofen. A well-studied gel-inducing supramolecular synthon, namely primary ammonium monocarboxylate (PAM), has been exploited to generate a series of PAM salts by reacting ibuprofen with various primary amines. Remarkably, all of the salts (S1-S7) thus synthesized proved to be good to moderate gelators of various polar and nonpolar solvents. Single-crystal and powder X-ray diffraction studies established the existence of the PAM synthons in the gel network, confirming the efficacy of the supramolecular synthon approach employed. Most importantly, the majority of the salts (S2, S3, S6, and S7) were capable of gelling methyl salicylate (MS), an important ingredient found in many commercial topical gels. In vitro experiments (MTT and PGE2 assays) revealed that all of the salts (except S3 and S7) were biocompatible (up to 0.5 mm concentration), and the most suited one, S6, displayed anti-inflammatory ability as good as that of the parent drug ibuprofen. A topical gel of S6 with methyl salicylate and menthol was found to be suitable for delivering the gelator drug in a self-delivery fashion in treating skin inflammation in mice. Histological studies, including immunohistology, were performed to further probe the role of the gelator drug S6 in treating inflammation. Cell imaging studies supported cellular uptake of the gelator drug in such biomedical application.

A self-assembling β-peptide hydrogel for neural tissue engineering

We report a new class of β-peptide based hydrogel for neural tissue engineering. Our β-peptide forms a network of nanofibres in aqueous solution, resulting in a stable hydrogel at physiological conditions. The hydrogel shows excellent compatibility with neural cells and provides a suitable environment for cells to adhere and proliferate.

Facile synthesis of a peptidic Au(I)-metalloamphiphile and its self-assembly into luminescent micelles in water

We report a short synthetic route for the preparation of a peptidic Au(I)-metalloamphiphile which, in buffered environments of physiological ionic strength, self-assembles into luminescent micellar nanostructures of 14 nm in diameter.

Self-assembled peptide-based nanostructures: Smart nanomaterials toward targeted drug delivery

Self-assembly of peptides can yield an array of well-defined nanostructures that are highly attractive nanomaterials for many biomedical applications such as drug delivery. Some of the advantages of self-assembled peptide nanostructures over other delivery platforms include their chemical diversity, biocompatibility, high loading capacity for both hydrophobic and hydrophilic drugs, and their ability to target molecular recognition sites. Furthermore, these self-assembled nanostructures could be designed with novel peptide motifs, making them stimuli-responsive and achieving triggered drug delivery at disease sites. The goal of this work is to present a comprehensive review of the most recent studies on self-assembled peptides with a focus on their "smart" activity for formation of targeted and responsive drug-delivery carriers.

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping address fundamental questions about the mechanisms or the consequences of the self-assembly of molecules, including low molecular weight ones. Finally, we provide a perspective on supramolecular hydrogelators. We hope that this review will serve as an updated introduction and reference for researchers who are interested in exploring supramolecular hydrogelators as molecular biomaterials for addressing the societal needs at various frontiers.

Bioprinting synthetic self-assembling peptide hydrogels for biomedical applications

Three-dimensional (3D) bioprinting is a disruptive technology for creating organotypic constructs for high-throughput screening and regenerative medicine. One major challenge is the lack of suitable bioinks. Short synthetic self-assembling peptides are ideal candidates. Several classes of peptides self-assemble into nanofibrous hydrogels resembling the native extracellular matrix. This is a conducive microenvironment for maintaining cell survival and physiological function. Many peptides also demonstrate stimuli-responsive gelation and tuneable mechanical properties, which facilitates extrusion before dispensing and maintains the shape fidelity of the printed construct in aqueous media. The inherent biocompatibility and biodegradability bodes well for in vivo applications as implantable tissues and drug delivery matrices, while their short length and ease of functionalization facilitates synthesis and customization. By applying self-assembling peptide inks to bioprinting, the dynamic complexity of biological tissue can be recreated, thereby advancing current biomedical applications of peptide hydrogel scaffolds.

Self-Assembled Proteins and Peptides as Scaffolds for Tissue Regeneration

Self-assembling proteins and peptides are increasingly gaining interest for potential use as scaffolds in tissue engineering applications. They self-organize from basic building blocks under mild conditions into supramolecular structures, mimicking the native extracellular matrix. Their properties can be easily tuned through changes at the sequence level. Moreover, they can be produced in sufficient quantities with chemical synthesis or recombinant technologies to allow them to address homogeneity and standardization issues required for applications. Here. recent advances in self-assembling proteins, peptides, and peptide amphiphiles that form scaffolds suitable for tissue engineering are reviewed. The focus is on a variety of motifs, ranging from minimalistic dipeptides, simplistic ultrashort aliphatic peptides, and peptide amphiphiles to large "recombinamer" proteins. Special emphasis is placed on the rational design of self-assembling motifs and biofunctionalization strategies to influence cell behavior and modulate scaffold stability. Perspectives for combination of these "bottom-up" designer strategies with traditional "top-down" biofabrication techniques for new generations of tissue engineering scaffolds are highlighted.

Peptide Bioink: Self-Assembling Nanofibrous Scaffolds for Three-Dimensional Organotypic Cultures

Printable scaffolds with adequate mechanical strength and stiffness are sought after to ensure viability of printed cells and tissues. We report the first peptide bioinks-lysine-containing hexapeptides that self-assemble into stable, nanofibrous three-dimensional hydrogels with unprecedented stiffness of up to 40 kPa. These biocompatible scaffolds support the three-dimensional culture of human stem cells and differentiation of primary cells into organotypic (gastrointestinal and skin) structures for high-throughput screening, diagnosis, and tissue engineering.

A supramolecular nanovehicle toward systematic, targeted cancer and tumor therapy

A supramolecular nanovehicle (denoted as SNV) was fabricated by encapsulating zinc phthalocyanine (ZnPc) and doxorubicin (DOX) into a copolymer (PVP-b-PAA-g-FA), so as to achieve systematic and synergistic chemotherapy-photodynamic therapy (PDT), targeted tumor imaging and therapy. The sophisticated copolymer designed in this work can load the PDT photosensitizer (ZnPc) and chemotherapy drug (DOX) simultaneously, which exhibits an excellent performance in chemotherapy-PDT targeted cancer and tumor therapy for both in vitro studies performed with HepG2 cells and in vivo tests with mice. This work provides a new drug formulation with a chemotherapy-PDT synergistic effect by virtue of the supramolecular material design, which possesses the advantages of an ultra-low drug dosage and highly-efficient in vivo targeted tumor imaging/therapy.

The Use of the Calcitonin Minimal Recognition Module for the Design of DOPA-Containing Fibrillar Assemblies

Amyloid deposits are insoluble fibrous protein aggregates, identified in numerous diseases, which self-assemble through molecular recognition. This process is facilitated by short amino acid sequences, identified as minimal modules. Peptides corresponding to these motifs can be used for the formation of amyloid-like fibrillar assemblies in vitro. Such assemblies hold broad appeal in nanobiotechnology due to their ordered structure and to their ability to be functionalized. The catechol functional group, present in the non-coded L-3,4-dihydroxyphenylalanine (DOPA) amino acid, can take part in diverse chemical interactions. Moreover, DOPA-incorporated polymers have demonstrated adhesive properties and redox activity. In this work, amyloid-like fibrillar assemblies were formed through the self-assembly of a pentapeptide containing DOPA residues, Asp-DOPA-Asn-Lys-DOPA. The design of this peptide was based on the minimal amyloidogenic recognition motif of the human calcitonin hormone, Asp-Phe-Asn-Lys-Phe, the first amyloidogenic pentapeptide identified. By substituting phenylalanine with DOPA, we obtained DOPA-functionalized amyloid-like assemblies in water. Electron microscopy revealed elongated, linear fibril-like nanometric assemblies. Secondary structure analysis indicated the presence of amyloid-characteristic β-sheet structures as well as random coil structures. Deposition of silver on the DOPA-incorporated assemblies suggested redox activity and demonstrated the applicative potential of this novel nanobiomaterial.

The first supramolecular peptidic hydrogelator containing taurine

The conjugation of taurine with a dipeptide derivative affords a cell compatible, small molecular hydrogelator to form hydrogels that exhibit rich phase transition behaviors in response to sonication and the change of pH or temperature.

Enzyme-triggered supramolecular self-assembly of platinum prodrug with enhanced tumor-selective accumulation and reduced systemic toxicity

A self-assembled Pt prodrug with enhanced drug accumulation in tumor areas was achieved through the catalysis of a locally expressed enzyme.