Drug-Bearing Supramolecular Filament Hydrogels as Anti-Inflammatory Agents

Application of Injectable Hydrogels as Delivery Systems in Osteoarthritis and Rheumatoid Arthritis

Osteoarthritis and rheumatoid arthritis, though etiologically distinct, are both inflammatory joint diseases that cause progressive joint injury, chronic pain, and loss of function. Therefore, long-term treatment with a focus on relieving symptoms is needed. At present, the primary treatment for arthritis is drug therapy, both oral and intravenous. Although significant progress has been achieved for these treatment methods in alleviating symptoms, certain prominent drawbacks such as the substantial side effects and limited absorption of medications call for an urgent need for improved drug delivery methods. Injected hydrogels can be used as a delivery system to deliver drugs to the joint cavity in a controlled manner and continuously release them, thereby enhancing drug retention in the joint cavity to improve therapeutic effectiveness, which is attributed to the desirable attributes of the delivery system such as low immunogenicity, good biodegradability and biocompatibility. This review summarizes the types of injectable hydrogels and analyzes their applications as delivery systems in arthritis treatment. We also explored how hydrogels counteract inflammation, bone and cartilage degradation, and oxidative stress, while promoting joint cartilage regeneration in the treatment of osteoarthritis (OA) and rheumatoid arthritis (RA). This review also highlights new approaches to developing injectable hydrogels as delivery systems for OA and RA.

Advances in Peptide-Decorated Targeted Drug Delivery: Exploring Therapeutic Potential and Nanocarrier Strategies

Peptides are ideal biologicals for targeted drug delivery and have also been increasingly employed as theranostic tools in treating various diseases, including cancer, with minimal or no side effects. Owing to their receptor-specificity, peptide-mediated drug delivery aids in targeted drug delivery with better pharmacological biodistribution. Nanostructured self-assembled peptides and peptide-drug conjugates demonstrate enhanced stability and performance and captivating biological effects in comparison with conventional peptides. Moreover, they serve as valuable tools for establishing interfaces between drug carriers and biological systems, enabling the traversal of multiple biological barriers encountered by peptide-drug conjugates on their journeys to their intended targets. Peptide-based drugs play a pivotal role in the field of medicine and hold great promise for addressing a wide range of complex diseases such as cancer and autoimmune disorders. Nanotechnology has revolutionized the fields of medicine, biomedical engineering, biotechnology, and engineering sciences over the past two decades. With the help of nanotechnology, better delivery of peptides to the target site could be achieved by exploiting the small size, increased surface area, and passive targeting ability of the nanocarrier. Furthermore, nanocarriers also ensure safe delivery of the peptide moieties to the target site, protecting them from degradation. Nanobased peptide delivery systems would be of significant importance in the near future for the successful targeted and efficient delivery of peptides. This review focuses on peptide-drug conjugates and nanoparticle-mediated self-assembled peptide delivery systems in cancer therapeutics.

In Situ Forming, Enzyme-Responsive Peptoid-Peptide Hydrogels: An Advanced Long-Acting Injectable Drug Delivery System

Long-acting drug delivery systems are promising platforms to improve patient adherence to medication by delivering drugs over sustained periods and removing the need for patients to comply with oral regimens. This research paper provides a proof-of-concept for the development of a new optimized in situ forming injectable depot based on a tetrabenzylamine-tetraglycine-d-lysine-O-phospho-d-tyrosine peptoid-D-peptide formulation ((NPhe)4GGGGk(AZT)y(p)-OH). The chemical versatility of the peptoid-peptide motif allows low-molecular-weight drugs to be precisely and covalently conjugated. After subcutaneous injection, a hydrogel depot forms from the solubilized peptoid-peptide-drug formulation in response to phosphatase enzymes present within the skin space. This system is able to deliver clinically relevant concentrations of a model drug, the antiretroviral zidovudine (AZT), for 35 days in Sprague-Dawley rats. Oscillatory rheology demonstrated that hydrogel formation began within ∼30 s, an important characteristic of in situ systems for reducing initial drug bursts. Gel formation continued for up to ∼90 min. Small-angle neutron scattering data reveal narrow-radius fibers (∼0.78-1.8 nm) that closely fit formation via a flexible cylinder elliptical model. The inclusion of non-native peptoid monomers and D-variant amino acids confers protease resistance, enabling enhanced biostability to be demonstrated in vitro. Drug release proceeds via hydrolysis of an ester linkage under physiological conditions, releasing the drug in an unmodified form and further reducing the initial drug burst. Subcutaneous administration of (NPhe)4GGGGk(AZT)y(p)-OH to Sprague-Dawley rats resulted in zidovudine blood plasma concentrations within the 90% maximal inhibitory concentration (IC90) range (30-130 ng mL-1) for 35 days.

Dual drug nanoparticle synergistically induced apoptosis, suppressed inflammation, and protected autophagic response in rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic immune-mediated joint inflammatory disorder associated with aberrant activation of fibroblast-like synoviocytes (FLS). Recently, FLS gained importance due to its crucial role in RA pathogenesis, and thus, targeting FLS is suggested as an attractive treatment strategy for RA. FLS-targeted approaches may be combined with disease-modifying antirheumatic drugs (DMARDs) and natural phytochemicals to improve efficacy in RA control and negate immunosuppression. In this study, we assessed the therapeutic effectiveness of DD NP HG in primary RA-FLS cells isolated from the synovial tissue of FCA-induced RA rats. We observed that DD NP HG had good biosafety for healthy FLS cells and, at higher concentrations, a mild inhibitory effect on RA-FLS. The combination therapy (DD NP HG) of MTX NP and PEITC NE in RA-FLS showed a higher rate of apoptosis with significantly reduced LPS-induced expression of pro-inflammatory cytokines (TNF-α, IL-17A, and IL-6) in arthritic FLS. Further, the gene expression studies showed that DD NP HG significantly down-regulated the mRNA expression of IL-1β, RANKL, NFATc1, DKK1, Bcl-xl, Mcl-1, Atg12, and ULK1, and up-regulated the mRNA expression of OPG, PUMA, NOXA and SQSTM1 in LPS-stimulated RA-FLS cells. Collectively, our results demonstrated that DD NP HG significantly inhibited the RA-FLS proliferation via inducing apoptosis, down-regulating pro-inflammatory cytokines, and further enhancing the expression of genes associated with bone destruction in RA pathogenesis. A nanotechnology approach is a promising strategy for the co-delivery of dual drugs to regulate the RA-FLS function and achieve synergistic treatment of RA.

Development of biomedical hydrogels for rheumatoid arthritis treatment

Rheumatoid Arthritis (RA) is an autoimmune disorder that hinders the normal functioning of bones and joints and reduces the quality of human life. Every year, millions of people are diagnosed with RA worldwide, particularly among elderly individuals and women. Therefore, there is a global need to develop new biomaterials, medicines and therapeutic methods for treating RA. This will improve the Healthcare Access and Quality Index and also relieve administrative and financial burdens on healthcare service providers at a global scale. Hydrogels are soft and cross-linked polymeric materials that can store a chunk of fluids, drugs and biomolecules for hydration and therapeutic applications. Hydrogels are biocompatible and exhibit excellent mechanical properties, such as providing elastic cushions to articulating joints by mimicking the natural synovial fluid. Hence, hydrogels create a natural biological environment within the synovial cavity to reduce autoimmune reactions and friction. Hydrogels also lubricate the articulating joint surfaces to prevent degradation of synovial surfaces of bones and cartilage, thus exhibiting high potential for treating RA. This work reviews the progress in injectable and implantable hydrogels, synthesis methods, types of drugs, advantages and challenges. Additionally, it discusses the role of hydrogels in targeted drug delivery, mechanistic behaviour and tribological performance for RA treatment.

Evaluation of the in vitro anti-inflammatory and anti-Helicobacter pylori activities of chitosan-based biomaterials modified with copper oxide nanoparticles

For chemical modification, p-aminobenzoic acid was incorporated into chitosan Schiff base (ACsSB) and chitosan (ACs). Two ACs-based CuO nanoparticles composites; ACs/CuONPs-1 % and ACs/CuONPs-5 %, were also synthesized. Their structures were emphasized utilizing several analytical techniques; elemental analysis, FTIR, 1H NMR, XRD, SEM, EDX and TEM. Compared with standard cyclooxygenase (COX) inhibitor, Celecoxib, the prepared biomaterials showed in vitro selective inhibitory effectiveness against COX-2 enzyme that could be sorted, according to their MIC values that produce 50 % inhibition of COX-2 enzyme activity, as follows: Celecoxib (0.28 μg/mL) > ACs/CuONPs-5 % (4.1 μg/mL) > ACs/CuONPs-1 % (14.8 μg/mL) > ACs (38.5 μg/mL) > ACsSB (58.9 μg/mL) > chitosan (>125 μg/mL). Further, ACs/CuONPs-5 % has more in vitro inhibition efficiency towards Helicobacter pylori (H. pylori) than the other prepared biomaterials. Interestingly, the MIC value of 100 % growth inhibition of H. pylori for ACs/CuONP-5 % is equal to that of drug Clarithromycin (1.95 μg/mL). Thus, ACs/CuONPs-5 % has a promising potential as anti-H. pylori and selective anti-inflammatory agent. ACs/CuONPs-5 % is safe on the human gastric normal cells (GES-1). Therefore, amalgamation of both p-aminobenzoic acid and CuONPs into chitosan extremely promoted its anti-inflammatory and anti-H. pylori activity. This is a promising approach to achieve methods successful to compete the conventional antibiotics.

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.

3D self-assembled nanocarriers for drug delivery

There are many benefits to drug delivery from drug-carrier nanostructure systems. It might be developed to carefully control drug release rates or to deliver a precise amount of a therapeutic substance to particular body areas. Self-assembling is the process by which molecules and nanoparticles spontaneously organize into organized clusters. For instance, proteins and peptides can interact with one another to create highly organized supramolecular structures with various properties, such as helical ribbons and fibrous scaffolds. Another advantage of self-assembly is that it may be effective with a variety of materials, including metals, oxides, inorganic salts, polymers, semiconductors, and even organic semiconductors. Fullerene, graphene, and carbon nanotubes (CNTs), three of the most fundamental classes of three-dimensionally self-assembling nanostructured carbon-based materials, are essential for the development of modern nanotechnologies. Self-assembled nanomaterials are used in a variety of fields, including nanotechnology, imaging, and biosensors. This review study begins with a summary of various major 3D nanomaterials, including graphene oxide, CNTs, and nanodiamond, as well as 3D self-assembled polyfunctionalized nanostructures and adaptable nanocarriers for drug delivery.

Hydrogels for the treatment of rheumatoid arthritis

Rheumatoid Arthritis is a universal disease that severely affects the normal function of human joints and the quality of life. Millions of people around the world are diagnosed with rheumatoid arthritis every year, carrying a substantial burden for both the individual and society. Hydrogel is a polymer material with good mechanical properties and biocompatibility, which shows great potential in the treatment of rheumatoid arthritis. With the progress of tissue engineering and biomedical material technology in recent years, more and more studies focus on the application of hydrogels in rheumatoid arthritis. We reviewed the progress of hydrogels applied in rheumatoid arthritis in recent years. Also, the needed comprehensive performance and current applications of therapeutic hydrogels based on the complex pathophysiological characteristics of rheumatoid arthritis are also concluded. Additionally, we proposed the challenges and difficulties in the application of hydrogels in rheumatoid arthritis and put forward some prospects for the future research.

Bioinspired Hydrogels as Platforms for Life-Science Applications: Challenges and Opportunities

Hydrogels, as interconnected networks (polymer mesh; physically, chemically, or dynamic crosslinked networks) incorporating a high amount of water, present structural characteristics similar to soft natural tissue. They enable the diffusion of different molecules (ions, drugs, and grow factors) and have the ability to take over the action of external factors. Their nature provides a wide variety of raw materials and inspiration for functional soft matter obtained by complex mechanisms and hierarchical self-assembly. Over the last decade, many studies focused on developing innovative and high-performance materials, with new or improved functions, by mimicking biological structures at different length scales. Hydrogels with natural or synthetic origin can be engineered as bulk materials, micro- or nanoparticles, patches, membranes, supramolecular pathways, bio-inks, etc. The specific features of hydrogels make them suitable for a wide variety of applications, including tissue engineering scaffolds (repair/regeneration), wound healing, drug delivery carriers, bio-inks, soft robotics, sensors, actuators, catalysis, food safety, and hygiene products. This review is focused on recent advances in the field of bioinspired hydrogels that can serve as platforms for life-science applications. A brief outlook on the actual trends and future directions is also presented.

Self-Assembling Peptide-Based Hydrogels for Wound Tissue Repair

Wound healing is a long-term, multistage biological process that includes hemostasis, inflammation, proliferation, and tissue remodeling and requires intelligent designs to provide comprehensive and convenient treatment. The complexity of wounds has led to a lack of adequate wound treatment materials, which must systematically regulate unique wound microenvironments. Hydrogels have significant advantages in wound treatment due to their ability to provide spatiotemporal control over the wound healing process. Self-assembling peptide-based hydrogels are particularly attractive due to their innate biocompatibility and biodegradability along with additional advantages including ligand-receptor recognition, stimulus-responsive self-assembly, and the ability to mimic the extracellular matrix. The ability of peptide-based materials to self-assemble in response to the physiological environment, resulting in functionalized microscopic structures, makes them conducive to wound treatment. This review introduces several self-assembling peptide-based systems with various advantages and emphasizes recent advances in self-assembling peptide-based hydrogels that allow for precise control during different stages of wound healing. Moreover, the development of multifunctional self-assembling peptide-based hydrogels that can regulate and remodel the wound immune microenvironment in wound therapy with spatiotemporal control has also been summarized. Overall, this review sheds light on the future clinical and practical applications of self-assembling peptide-based hydrogels.

BH3-mimetics: recent developments in cancer therapy

The hopeful outcomes from 30 years of research in BH3-mimetics have indeed served a number of solid paradigms for targeting intermediates from the apoptosis pathway in a variety of diseased states. Not only have such rational approaches in drug design yielded several key therapeutics, such outputs have also offered insights into the integrated mechanistic aspects of basic and clinical research at the genetics level for the future. In no other area of medical research have the effects of such work been felt, than in cancer research, through targeting the BAX-Bcl-2 protein-protein interactions. With these promising outputs in mind, several mimetics, and their potential therapeutic applications, have also been developed for several other pathological conditions, such as cardiovascular disease and tissue fibrosis, thus highlighting the universal importance of the intrinsic arm of the apoptosis pathway and its input to general tissue homeostasis. Considering such recent developments, and in a field that has generated so much scientific interest, we take stock of how the broadening area of BH3-mimetics has developed and diversified, with a focus on their uses in single and combined cancer treatment regimens and recently explored therapeutic delivery methods that may aid the development of future therapeutics of this nature.

Therapeutic supramolecular tubustecan hydrogel combined with checkpoint inhibitor elicits immunity to combat cancer

The clinical benefit of PD-1/PD-L1 blockade immunotherapy is substantially restricted by insufficient infiltration of T lymphocytes into tumors and compromised therapeutic effects due to immune-related adverse events following systemic administration. Some chemotherapeutic agents have been reported to trigger tumor-associated T cell responses, providing a promising strategy to achieve potent immune activation in a synergistic manner with PD-1 blockade immunotherapy. In light of this, a localized chemoimmunotherapy system was developed using an anti-cancer drug-based supramolecular polymer (SP) hydrogel to "re-edit" the host's immune system to combat cancer. This in situ forming injectable aPD1/TT6 SP hydrogel serves as a drug-delivery depot for sustained release of bioactive camptothecin (CPT) and aPD1 into the tumor microenvironment, priming the tumor for robust infiltration of tumor-associated T cells and subsequently prompting a response to the immune checkpoint blockade. Our in vivo results demonstrate that this chemoimmunotherapy hydrogel provokes a long-term and systemic anticancer T cell immune response, which elicits tumor regression while also inhibiting tumor recurrence and potential metastasis.

Innate tumor-targeted nanozyme overcoming tumor hypoxia for cancer theranostic use

Introduction

Hypoxic tumor microenvironment (TME) is the major contributor to cancer metastasis, resistance to chemotherapy, and recurrence of tumors. So far, no approved treatment has been available to overcome tumor hypoxia.

Objectives

The present study aimed to relieve tumor hypoxia via a nanozyme theranostic nanomaterial as well as providing magnetic resonance imaging (MRI)-guided therapy.

Methods

Manganese dioxide (MnO₂) was used for its intrinsic enzymatic activity co-loaded with the anti-cancer drug Doxorubicin (Dox) within the recombinant heavy-chain apoferritin cavity to form MnO₂-Dox@HFn. Following the synthesis of the nanomaterial, different characterizations were performed as well as its nanozyme-like ability. This nanoplatform recognizes tumor cells through the transferrin receptors 1 (TfR1) which are highly expressed on the surface of most cancer cells. The cellular uptake was confirmed by flow cytometry and fluorescence spectroscopy. In vitro and in vivo studies have been investigated to evaluate the hypoxia regulation, MRI ability and anti-tumor activity of MnO₂-Dox@HFn.

Results

Being a TME-responsive nanomaterial, MnO₂-Dox@HFn exerted both peroxidase and catalase activity that mainly produce massive oxygen and Mn²⁺ ions. Respectively, these products relieve the unfavorable tumor hypoxia and also exhibit T1-weighted MRI with a high longitudinal relaxivity of 33.40 mM. s⁻¹. The utility of MnO₂-Dox@HFn was broadened with their efficient anti-cancer activity proved both in vitro and in vivo.

Conclusions

MnO₂-Dox@HFn successfully overcome tumor hypoxia with double potentials enzymatic ability and diagnostic capacity. This investigation could ignite the future application for cancer theranostic nanozyme therapy.

Self-assembling peptides as vectors for local drug delivery and tissue engineering applications

Molecular self-assembly has forged a new era in the development of advanced biomaterials for local drug delivery and tissue engineering applications. Given their innate biocompatibility and biodegradability, self-assembling peptides (SAPs) have come in the spotlight of such applications. Short and water-soluble SAP biomaterials associated with enhanced pharmacokinetic (PK) and pharmacodynamic (PD) responses after the topical administration of the therapeutic systems, or improved regenerative potential in tissue engineering applications will be the focus of the current review. SAPs are capable of generating supramolecular structures using a boundless array of building blocks, while peptide engineering is an approach commonly pursued to encompass the desired traits to the end composite biomaterials. These two elements combined, expand the spectrum of SAPs multi-functionality, constituting them potent biomaterials for use in various biomedical applications.

Multifunctional nanorods based on self-assembly of biomimetic apolipoprotein E peptide for the treatment of Alzheimer's disease

Targeting a single molecule or a single pathway and poor drug delivery to the brain hamper the therapy of Alzheimer's disease (AD) based on abnormal metabolism of amyloid-β (Aβ). To solve these problems, we designed and synthesized a multi - strategy peptide (MOP), an ingenious apolipoprotein E mimetic peptide, which could reduce Aβ deposition via inhibiting Aβ aggregation and at the same time accelerate Aβ clearance. Meanwhile, MOP could be self-assembled into different nanostructure, thus we constructed a multifunctional delivery system (APND-3) based on MOP self-assembled nanorods (aspect ratios of 3) that was a favorable morphology to enhance the permeation across the blood brain barrier (BBB) to address the poor delivery to brain issues. Besides, the drug delivery system introduces polydopamine (PDA) and COG1410 ligand as a shell to keep the favorable morphology of core and enhance the BBB targeting efficiency. As a result, the delivery system significantly enhances the delivery of MOP to the brain, thus reducing Aβ deposition, mitigating the memory deficits, and ameliorating neurologic damage in AD model mice. Our findings suggest that our drug and carrier integrated multifunctional delivery system has the potential for AD treatment.

Matrix Metalloproteinase-9-Responsive Surface Charge-Reversible Nanocarrier to Enhance Endocytosis as Efficient Targeted Delivery System for Cancer Diagnosis and Therapy

Nanoparticles, that can be enriched in the tumor microenvironment and deliver the payloads into cancer cells, are desirable carriers for theranostic agents in cancer diagnosis and treatment. However, efficient targeted delivery and enhanced endocytosis for probes and drugs in theranostics are still major challenges. Here, a nanoparticle, which is capable of charge reversal from negative to positive in response to matrix metalloproteinase 9 (MMP9) in tumor microenvironment is reported. This nanoparticle is based on a novel charge reversible amphiphilic molecule consisting of hydrophobic oleic acid, MMP9-cleavable peptide, and glutamate-rich segment (named as OMPE). The OMPE-modified cationic liposome forms an intelligent anionic nanohybrid (O-NP) with enhanced endocytosis through surface charge reversal in response to MMP9 in vitro. Successfully, O-NP nanohybrid performs preferential accumulation and enhances the endocytosis in MMP9-expressing xenografted tumors in mouse models, which improve the sensitivity of diagnosis agents and the antitumor effects of drugs in vivo by overcoming their low solubility and/or nonspecific enrichment. These results indicate that O-NP can be a promising delivery platform for cancer diagnosis and therapy.

Synthesis, characterization, anti-inflammatory and anti-Helicobacter pylori activities of novel benzophenone tetracarboxylimide benzoyl thiourea cross-linked chitosan hydrogels

Chitosan (Cs) was cross-linked with four various quantities of 4,4'-(5,5'‑carbonylbis(1,3-dioxoisoindoline-5,2-diyl))dibenzoyl isothiocyanate. Elemental analysis, FTIR and ¹H NMR spectroscopy assured that the amino groups of chitosan reacted with the isothiocyanate groups of the cross-linker producing four new hydrogels namely as BBTU-Cs-1, BBTU-Cs-2, BBTU-Cs-3, and BBTU-Cs-4 according to the increment of their cross-linking content, respectively. SEM showed their porous structures and XRD indicated their amorphous nature. Their swell ability increased with decreasing the medium pH value and with increasing cross-linking density. In comparison with the popular COX inhibitor Celecoxib, these hydrogels showed an inhibition activity towards COX enzymes with selective inhibition towards COX-2. Their inhibition activity could be arranged as follows: Celecoxib > BBTU-Cs-4 > BBTU-Cs-3 > BBTU-Cs-2 > BBTU-Cs-1. BBTU-CS-4 hydrogel exhibited a potent inhibition against COX-2 (IC₅₀ 0.42 μg/ml) compared with that observed for the standard Celecoxib (IC₅₀ 0.26 μg/ml). BBTU-Cs-4 is more potent against H. pylori compared to the other hydrogels. BBTU-Cs-4 at a concentration of 7.81 μg/ml is able to kill 100% of the H. pylori and exhibits a preferential ability to inhibit 89.35% of COX-2 than COX-1 (0%). These findings make BBTU-Cs-4 a promising anti-H. pylori and selective anti-inflammatory agent.

Dehydropeptide Supramolecular Hydrogels and Nanostructures as Potential Peptidomimetic Biomedical Materials

Supramolecular peptide hydrogels are gaining increased attention, owing to their potential in a variety of biomedical applications. Their physical properties are similar to those of the extracellular matrix (ECM), which is key to their applications in the cell culture of specialized cells, tissue engineering, skin regeneration, and wound healing. The structure of these hydrogels usually consists of a di- or tripeptide capped on the N-terminus with a hydrophobic aromatic group, such as Fmoc or naphthalene. Although these peptide conjugates can offer advantages over other types of gelators such as cross-linked polymers, they usually possess the limitation of being particularly sensitive to proteolysis by endogenous proteases. One of the strategies reported that can overcome this barrier is to use a peptidomimetic strategy, in which natural amino acids are switched for non-proteinogenic analogues, such as D-amino acids, β-amino acids, or dehydroamino acids. Such peptides usually possess much greater resistance to enzymatic hydrolysis. Peptides containing dehydroamino acids, i.e., dehydropeptides, are particularly interesting, as the presence of the double bond also introduces a conformational restraint to the peptide backbone, resulting in (often predictable) changes to the secondary structure of the peptide. This review focuses on peptide hydrogels and related nanostructures, where α,β-didehydro-α-amino acids have been successfully incorporated into the structure of peptide hydrogelators, and the resulting properties are discussed in terms of their potential biomedical applications. Where appropriate, their properties are compared with those of the corresponding peptide hydrogelator composed of canonical amino acids. In a wider context, we consider the presence of dehydroamino acids in natural compounds and medicinally important compounds as well as their limitations, and we consider some of the synthetic strategies for obtaining dehydropeptides. Finally, we consider the future direction for this research area.

Recent Progress in the Design and Application of Supramolecular Peptide Hydrogels in Cancer Therapy

Supramolecular peptide hydrogel (SPH) is a class of biomaterials self-assembled from peptide-based gelators through non-covalent interactions. Among many of its biomedical applications, the potential of SPH in cancer therapy has been vastly explored in the past decade, taking advantage of its good biocompatibility, multifunctionality, and injectability. SPHs can exert localized cancer therapy and induce systemic anticancer immunity to prevent tumor recurrence, depending on the design of SPH. This review first gives a brief introduction to SPH and then outlines the major types of peptide-based gelators that have been developed so far. The methodologies to tune the physicochemical properties and biological activities are summarized. The recent advances of SPH in cancer therapy as carriers, prodrugs, or drugs are highlighted. Finally, the clinical translation potential and main challenges in this field are also discussed.

Exploring the properties and potential biomedical applications of NSAID-capped peptide hydrogels

The development of strategies to minimise the adverse side-effects of non-steroidal anti-inflammatory drugs (NSAIDs) remains a challenge for medicinal chemists. One such strategy is the development of NSAID-peptide prodrug conjugates and this conjugation to a peptide often confers the additional property of hydrogelation. This review summarises the work published by our research group, alongside other research groups, on supramolecular hydrogels consisting of short peptides conjugated to NSAIDs. Generally, supramolecular low molecular weight hydrogels (LMWHs) are composed of amphiteric molecules, usually consisting of short peptides attached to an aromatic capping group. When the aromatic capping group is switched for an NSAID to afford hybrid gelators, some conjugates exhibit retained or improved anti-inflammatory properties of the parent drug, and sometimes new and unexpected biological activities are observed. Conjugation to peptides often provides selective COX-2 inhibition over COX-1 inhibtion, which is key to retaining the anti-inflammatory benefits of NSAIDs whilst minimising gastric side-effects. Naproxen is the most commonly employed NSAID capping group, partly due to its similarity in structure to commonly employed naphthalene capping groups. Biomimetic approaches, where canonical amino acids are switched for non-natural amino acids such as d-amino acids or dehydroamino acids, are often employed, to tune the stability. The future direction for this area of research is discussed.

Self-assembling Peptides in Current Nanomedicine: Versatile Nanomaterials for Drug Delivery

BACKGROUND

The development of modern nanomedicine greatly depends on the involvement of novel materials as drug delivery system. In order to maximize the therapeutic effects of drugs and minimize their side effects, a number of natural or synthetic materials have been widely investigated for drug delivery. Among these materials, biomimetic self-assembling peptides (SAPs) have received more attention in recent years. Considering the rapidly growing number of SAPs designed for drug delivery, a summary of how SAPs-based drug delivery systems were designed, would be beneficial.

METHOD

We outlined research works on different SAPs that have been investigated as carriers for different drugs, focusing on the design of SAPs nanomaterials and how they were used for drug delivery in different strategies.

RESULTS

Based on the principle rules of chemical complementarity and structural compatibility, SAPs such as ionic self-complementary peptide, peptide amphiphile and surfactant-like peptide could be designed. Determined by the features of peptide materials and the drugs to be delivered, different strategies such as hydrogel embedding, hydrophobic interaction, electrostatic interaction, covalent conjugation or the combination of them could be employed to fabricate SAPs-drug complex, which could achieve slow release, targeted or environment-responsive delivery of drugs. Furthermore, some SAPs could also be combined with other types of materials for drug delivery, or even act as drug by themselves.

CONCLUSION

Various types of SAPs have been designed and used for drug delivery following various strategies, suggesting that SAPs as a category of versatile nanomaterials have promising potential in the field of nanomedicine.

Hyaluronic acid-shelled, peptide drug conjugate-cored nanomedicine for the treatment of hepatocellular carcinoma

Peptide-drug conjugate (PDC) is a promising prodrug in drug delivery systems. To fabricate nanostructures with proper molecular design which can self-assemble to spherical morphologies is very important for PDC chemotherapy. In this study, a novel PDC (PDC-DOX₂), in which two doxorubicin (DOX) molecules are conjugated onto a short peptide (KIGLFRWR) with self-assembly function, was designed and synthesized. PDC-DOX₂ with self-assembly properties forms a spherical structure under hydrophobic interaction in water. Hyaluronic acid (HA) was then coated on PDC-DOX₂ micelles to form a HA-shelled, peptide-doxorubicin conjugate-cored nanomedicine (HA@PDC-DOX₂). The amount of HA can regulate the particle size and stabilization of HA@PDC-DOX₂. In addition, HA can actively enhance the targeting effects of PDC-DOX₂ micelles since it can interact with overexpressed receptors in cancer cells. The core-shell structured HA@PDC-DOX₂ nanomedicine showed significantly enhanced potency against hepatocellular carcinoma compared to PDC-DOX₂ micelles as well as free DOX. In this work, a novel PDC which can self-assemble to spherical morphologies and a core-shell structure HA@PDC-DOX₂ nanomedicine are designed and prepared. It provides a convenient strategy for the size control of PDC assemblies and constructs effective PDC-based drug delivery systems for cancer treatment.

Supramolecular Tubustecan Hydrogel as Chemotherapeutic Carrier to Improve Tumor Penetration and Local Treatment Efficacy

Local chemotherapy is a clinically proven strategy in treating malignant brain tumors. Its benefits, however, are largely limited by the rapid release and clearance of therapeutic agents and the inability to penetrate through tumor tissues. We report here on a supramolecular tubustecan (TT) hydrogel as both a therapeutic and drug carrier that enables long-term, sustained drug release and improved tumor tissue penetration. Covalent linkage of a tissue penetrating cyclic peptide to two camptothecin drug units creates a TT prodrug amphiphile that can associate into tubular supramolecular polymers and subsequently form a well-defined sphere-shaped hydrogel after injection into tumor tissues. The hollow nature of the resultant tubular assemblies allows for encapsulation of doxorubicin or curcumin for combination therapy. Our in vitro and in vivo studies reveal that these dual drug-bearing supramolecular hydrogels enhance tumor retention and penetration, serving as a local therapeutic depot for potent tumor regression, inhibition of tumor metastasis and recurrence, and mitigation of the off-target side effects.

Bifunctional supramolecular nanofiber inhibits atherosclerosis by enhancing plaque stability and anti-inflammation in apoE-/- mice

Background and Purpose: Atherosclerosis is vascular disease of chronic inflammation and lipid disorder, which is a major cause of coronary heart disease. Foam cell formation is key progress during the atherosclerosis development. Insulin-like growth factor (IGF)-1 is a growth hormone that plays a crucial role in growth, metabolism, and homeostasis. Previous studies have demonstrated that increase in circulating IGF-1 can reduce atherosclerotic burden. However, active IGF-1 is characterized with poor tissue retention and is at a very low level in circulation system. Therefore, supplementation of exogenous IGF-1 to restore the physiological level is a promising approach to inhibit atherosclerosis. In this study, we develop a self-assembling, anti-inflammatory drug-modified peptide derived from IGF-1 to mimic IGF-1 bioactivity and simultaneously with an anti-inflammatory property for the treatment of atherosclerosis.

Methods: ApoE^-/- mice were subcutaneously (s.c.) injected with the different hydrogels or natural IGF-1 protein solution per week and simultaneously fed a high-fat diet for 16 weeks. Atherosclerotic lesion formation and stability were assessed after treatment. Moreover, peritoneal macrophage and serum samples were collected to determine lipid profile and inflammatory cytokines. Concurrently, we determined the effect of bifunctional supramolecular nanofibers/hydrogel on cholesterol efflux, foam cell formation, phenotypic transformation of VSMC to macrophage-like cells, and macrophage polarization in vitro or in vivo.

Results: Bifunctional supramolecular nanofibers/hydrogel for the treatment of atherosclerosis was formed by a short peptide consisting of a tetrapeptide SSSR from C-region of growth factor IGF-1, an anti-inflammatory drug naproxen (Npx), and a powerful self-assembling D-peptide ^DF^DF. The resulting hydrogel of Npx-^DF^DFGSSSR (Hydrogel 1, H1) possessed both the anti-inflammatory and IGF-1 mimicking properties, and it efficiently promoted the expression of ABCA1 and ABCG1, thereby significantly reducing cholesterol accumulation in macrophages and preventing foam cell formation. Moreover, H1 markedly inhibited the transformation of vascular smooth muscle cells (VSMCs) into macrophage-like cells which also contributed to foam cell formation. In addition, H1 significantly reduced the inflammatory response in vitro and in vivo. Most importantly, the IGF-1 mimetic peptide showed comparable performance to IGF-1 in vivo and inhibited atherosclerosis by markedly reducing lesion area and enhancing plaque stability.

Conclusions: Our study provides a novel supramolecular nanomaterial to inhibit pathological progress of atherosclerosis through regulating cholesterol efflux and inflammation, which may contribute to the development of a promising nanomedicine for the treatment of atherosclerosis in the clinic.

Metal ions modulation of the self-assembly of short peptide conjugated nonsteroidal anti-inflammatory drugs (NSAIDs)

Metal ions are essential components that help maintain the processes of normal life, and they can be used to fabricate self-assembled building blocks for peptide derivatives, proteins and nucleic acids. Here, we have developed a novel strategy to construct supramolecular hydrogels modulated using metal cations. Upon introducing a variety of metal ions into aqueous solutions of a gelator (naproxen-FF), including a nonsteroidal anti-inflammatory drug (NSAID) and dipeptide, we obtain stable hydrogels under neutral or alkaline conditions. It is found that these hydrogels with three-dimensional nanofiber networks exhibit excellent mechanical properties and thixotropy, as well as superb responsivity to multiple metal ions. Due to the significance of potassium ions in biological processes, the K-triggered hydrogel has been chosen as a model, and its self-assembly mechanism has been explored via various spectral analysis processes. In addition, the self-assembly performances of peptides are significantly affected by the chemical structures of the gelator molecules. This work provides deep insight into the aggregation mechanism of dipeptide-conjugating drug molecules through introducing a variety of metal ions, laying the foundation for further biological applications.

Biological Evaluation of Naproxen-Dehydrodipeptide Conjugates with Self-Hydrogelation Capacity as Dual LOX/COX Inhibitors

The use of peptide-drug conjugates is emerging as a powerful strategy for targeted drug delivery. Previously, we have found that peptides conjugated to a non-steroidal anti-inflammatory drug (NSAID), more specifically naproxen-dehydrodipeptide conjugates, readily form nanostructured fibrilar supramolecular hydrogels. These hydrogels were revealed as efficacious nano-carriers for drug delivery applications. Moreover, the incorporation of superparamagnetic iron oxide nanoparticles (SPIONs) rendered the hydrogels responsive to external magnetic fields, undergoing gel-to-solution phase transition upon remote magnetic excitation. Thus, magnetic dehydrodipeptide-based hydrogels may find interesting applications as responsive Magnetic Resonance Imaging (MRI) contrast agents and for magnetic hyperthermia-triggered drug-release applications. Supramolecular hydrogels where the hydrogelator molecule is endowed with intrinsic pharmacological properties can potentially fulfill a dual function in drug delivery systems as (passive) nanocariers for incorporated drugs and as active drugs themselves. In this present study, we investigated the pharmacological activities of a panel of naproxen-dehydrodipeptide conjugates, previously studied for their hydrogelation ability and as nanocarriers for drug-delivery applications. A focused library of dehydrodipeptides, containing N-terminal canonical amino acids (Phe, Tyr, Trp, Ala, Asp, Lys, Met) N-capped with naproxen and linked to a C-terminal dehydroaminoacid (ΔPhe, ΔAbu), were evaluated for their anti-inflammatory and anti-cancer activities, as well as for their cytotoxicity to non-cancer cells, using a variety of enzymatic and cellular assays. All compounds except one were able to significantly inhibit lipoxygenase (LOX) enzyme at a similar level to naproxen. One of the compounds 4 was able to inhibit the cyclooxygenase-2 (COX-2) to a greater extent than naproxen, without inhibiting cyclooxygenase-1 (COX-1), and therefore is a potential lead in the search for selective COX-2 inhibitors. This hydrogelator is a potential candidate for dual COX/LOX inhibition as an optimised strategy for treating inflammatory conditions.

Hyaluronic acid hydrophilic surface rehabilitating curcumin nanocrystals for targeted breast cancer treatment with prolonged biodistribution

Due to its high therapeutic efficiency and low systemic toxicity, natural bioactive curcumin has attracted more and more attention as a potential antineoplastic drug.

Recent advances on small-molecule nanomedicines for cancer treatment

Nanomedicines have made important contributions in the development of cancer therapies due to their tumor selectivity, multifunctionality, and synergistic effect between the payloads. In addition to the required pharmaceutical ingredients, nanomedicines are generally composed of nonpharmaceutical excipients. These excipients generally form a large proportion of the nanomedicine, and they may have potential toxicity and greatly increase the cost for drug development. Small molecule nanomedicines (SMNs) minimize or abandon the excipients and are directly assembled from pharmaceutical ingredients, which can largely improve the drug delivery efficiency and biosafety while also relieving the financial burden of drug development. In this review, we summarize recently developed SMNs that are composed of a single drug, physical mixtures of multiple drugs, drug-drug covalent conjugates, dyes with drugs, photosensitizers with drugs, photosensitizers with peptides, and drugs with peptides. This review focuses on the SMN's applications in cancer treatments, their limitations, and the future development outlook of SMNs. We hope that our insights on SMNs may be helpful to the future of drug development and make nanomedicine more powerful in the battle with cancer. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

ROS-Mediated Apoptosis and Anticancer Effect Achieved by Artesunate and Auxiliary Fe(II) Released from Ferriferous Oxide-Containing Recombinant Apoferritin

Reactive oxygen species (ROS)-mediated apoptosis is considered a crucial therapeutic mechanisms for artesunate (AS). As an Fe(II)-dependent drug, the anticancer effect of AS is often limited due to insufficient Fe(II) concentration in targeted cells. To overcome this problem, a recombinant apoferritin nanocarrier containing ferriferous oxide (M-HFn) is constructed to produce auxiliary exogenous Fe(II) when delivering AS to cancer cells. Here, the newly fabricated AS-loaded M-HFn nanoparticles (M-HFn@AS NPs) can significantly improve the tumor-specific targeting and intracellular uptake efficiency of AS in human cervical carcinoma cells. After being captured in the acidic cavity of endosomes, M-HFn@AS NPs can simultaneously release Fe(II) and allow AS to activate satisfactory ROS-mediated apoptosis. Furthermore, in vivo studies demonstrate that M-HFn@AS NPs can selectively accumulate in tumors to efficiently inhibit tumor growth. Thus, M-HFn@AS NPs are a promising system to enhance the therapeutic effect of Fe(II)-dependent drugs.

Injectable peptide hydrogel as intraperitoneal triptolide depot for the treatment of orthotopic hepatocellular carcinoma

Chemotherapy is among the limited choices approved for the treatment of hepatocellular carcinoma (HCC) at intermediate and advanced stages. Preferential and prolonged drug exposure in diseased sites is required to maximize the therapeutic index of the drug. Here, we report an injectable supramolecular peptide hydrogel as an intraperitoneal depot for localized and sustained release of triptolide for the treatment of orthotopic HCC. We chose peptide amphiphile C₁₆-GNNQQNYKD-OH-based nanofibers as gelators and carriers for triptolide. Sustained triptolide release from the hydrogel was achieved over 14 days in vitro, with higher accumulation in and cytotoxicity against human HCC Bel-7402 in comparison with L-02 fetal hepatocytes. After intraperitoneal injection, the hydrogel showed prolonged retention over 13 days and preferential accumulation in the liver, realizing HCC growth inhibition by 99.7 ± 0.1% and animal median survival extension from 19 to 43 days, without causing noticeable pathological changes in the major organs. These results demonstrate that injectable peptide hydrogel can be a potential carrier for localized chemotherapy of HCC.

Fine-Tuning the Linear Release Rate of Paclitaxel-Bearing Supramolecular Filament Hydrogels through Molecular Engineering

One key design feature in the development of any local drug delivery system is the controlled release of therapeutic agents over a certain period of time. In this context, we report the characteristic feature of a supramolecular filament hydrogel system that enables a linear and sustainable drug release over the period of several months. Through covalent linkage with a short peptide sequence, we are able to convert an anticancer drug, paclitaxel (PTX), to a class of prodrug hydrogelators with varying critical gelation concentrations. These self-assembling PTX prodrugs associate into filamentous nanostructures in aqueous conditions and consequently percolate into a supramolecular filament network in the presence of appropriate counterions. The intriguing linear drug release profile is rooted in the supramolecular nature of the self-assembling filaments which maintain a constant monomer concentration at the gelation conditions. We found that molecular engineering of the prodrug design, such as varying the number of oppositely charged amino acids or through the incorporation of hydrophobic segments, allows for the fine-tuning of the PTX linear release rate. In cell studies, these PTX prodrugs can exert effective cytotoxicity against glioblastoma cell lines and also primary brain cancer cells derived from patients and show enhanced tumor penetration in a cancer spheroid model. We believe this drug-bearing hydrogel platform offers an exciting opportunity for the local treatment of human diseases.

Supramolecular Nanotheranostics

This supramolecular nanotheranostics special issue collected a total of 17 review articles and 3 research articles broadly covering the current and emerging supramolecular nanotheranostics.

"Locked" cancer cells are more sensitive to chemotherapy

The treatment of metastatic cancer is a great challenging issue throughout the world. Conventional chemotherapy can kill the cancer cells and, whereas, would exacerbate the metastasis and induce drug resistance. Here, a new combinatorial treatment strategy of metastatic cancer was probed via subsequentially dosing dual nanomedicines, marimastat-loaded thermosensitive liposomes (MATT-LTSLs) and paclitaxel nanocrystals (PTX-Ns), via intravenous and intratumoral injection. First, the metastasis was blocked and cancer cells were locked in the tumor microenvironment (TME) by delivering the matrix metalloproteinase (MMP) inhibitor, MATT, to the tumor with LTSLs, downregulating the MMPs by threefold and reducing the degradation of the extracellular matrix. And then, the "locked" cancer cells were efficiently killed via intratumoral injection of the other cytotoxic nanomedicine, PTX-Ns, along with no metastasis and 100% inhibition of tumor growth. This work highlights the importance of the TME's integrity in the chemotherapy duration. We believe this is a generalized strategy for cancer treatment and has potential guidance for the clinical administration.

Transdermal delivery of curcumin-loaded supramolecular hydrogels for dermatitis treatment

Curcumin (CUR) is a hydrophobic polyphenol with anti-inflammatory activity. However, its low water-solubility and poor skin permeation limited its application in the treatment of dermititis. CUR-loaded micelles were prepared using thin membrane hydration method with methoxy poly (ethylene glycol)-block-poly (ε-caprolactone) (MPEG-PCL) as carrier material. The drug loading capacity and encapsulation efficiency were 12.14 ± 0.33 and 93.57 ± 1.67%, respectively. CUR-loaded micelles increased CUR's water-solubility to 1.87 mg/mL, being 1.87 × 10⁶-folds higher than native CUR. CUR-loaded supramolecular hydrogels (CUR-H) were prepared through mixing the CUR-loaded micelles solution with α-cyclodextrin (α-CD) solution. The CUR-H presented continuous dissolution behaviour in aqueous medium for 4.5 h. The ex vivo skin permeation test and confocal fluorescence microscopy evaluation confirmed that CUR-H obviously enhanced skin deposition of CUR without drug flux from skin. In vivo experimental results confirmed that the CUR-H was more effective than dexamethasone ointments against croton oil-induced ear edema. The CUR-H composed of MPEG-PCL and α-CD is a promising formulation for skin inflammatory treatment.

Drug-Bearing Supramolecular MMP Inhibitor Nanofibers for Inhibition of Metastasis and Growth of Liver Cancer

Treatment of hepatocellular carcinoma (HCC) requires sustained suppression of tumor cell growth and metastasis for long-term efficacy. However, traditional intratumoral drug delivery system always exhibits burst release with less therapeutic outcomes. Here, a new self-assembling amphiphilic peptide drug conjugate (SAAPDC) is fabricated as a "two-in-one" nanofiber system comprising a hexapeptide as a matrix metalloproteinases (MMP) inhibitor and doxorubicin (DOX) for the treatment of HCC. The results indicate that doxorubicin-conjugated peptide (DOX-KGFRWR) self-assembles to form long nanofibers showing sustained release property for inhibiting the enzymatic activities of MMP-2 and MMP-9. This nanofiber not only inhibits tumor growth in situ but also effectively prevents pulmonary metastasis in an SMMC7721 cell line-based mouse model. In summary, this hexapeptide-based supermolecule system represents a promising nanoscale platform to sustain drug release with high loading capacity for intratumoral administration. Moreover, the delivery of chemotherapeutic drugs via drug-bearing supramolecular MMP inhibitor nanofibers simultaneously inhibits metastasis and tumor growth to achieve synergistic effects for metastatic HCC therapy.

Near-infrared light-controlled regulation of intracellular calcium to modulate macrophage polarization

Macrophages are multifunctional immune cells with diverse physiological functions such as fighting against infection, influencing progression of pathologies, maintaining homeostasis, and regenerating tissues. Macrophages can be induced to adopt distinct polarized phenotypes, such as classically activated pro-inflammatory (M1) phenotypes or alternatively activated anti-inflammatory and pro-healing (M2), to execute diverse and dynamic immune functions. However, unbalanced polarizations of macrophage can lead to various pathologies, such as atherosclerosis, obesity, tumor, and asthma. Thus, the capability to remotely control macrophage phenotypes is important to the success of treating many pathological conditions involving macrophages. In this study, we developed an upconversion nanoparticle (UCNP)-based photoresponsive nanocarrier for near-infrared (NIR) light-mediated control of intracellular calcium levels to regulate macrophage polarization. UCNP was coated with mesoporous silica (UCNP@mSiO₂), into which loaded calcium regulators that can either supply or deplete calcium ions. UCNP@mSiO₂ was chemically modified through serial coupling of photocleavable linker and Arg-Gly-Asp (RGD) peptide-bearing molecular cap via cyclodextrin-adamantine host-guest complexation. The RGD-bearing cap functioned as the photolabile gating structure to control the release of calcium regulators and facilitated the cellular uptake of UCNP@mSiO₂ nanocarrier. The upconverted UV light emission from the UCNP@mSiO₂ under NIR light excitation triggered the cleavage of cap and intracellular release of calcium regulators, thereby allowing temporal regulation on the intracellular calcium levels. Application of NIR light through skin tissue promoted M1 or M2 polarization of macrophages, by elevating or depleting intracellular calcium levels, respectively. To the best of our knowledge, this is the first demonstration of NIR light-mediated remote control on macrophage polarization. This photoresponsive nanocarrier offers the potential to remotely manipulate in vivo immune functions, such as inflammation or tissue regeneration, via NIR light-controlled macrophage polarization.

Self-assembly behaviours of peptide-drug conjugates: influence of multiple factors on aggregate morphology and potential self-assembly mechanism

Peptide-drug conjugates (PDCs) as self-assembly prodrugs have the unique and specific features to build one-component nanomedicines. Supramolecular structure based on PDCs could form various morphologies ranging from nanotube, nanofibre, nanobelt to hydrogel. However, the assembly process of PDCs is too complex to predict or control. Herein, we investigated the effects of extrinsic factors on assembly morphology and the possible formation of nanostructures based on PDCs. To this end, we designed a PDC consisting of hydrophobic drug (S)-ketoprofen (Ket) and valine-glutamic acid dimeric repeats peptide (L-VEVE) to study their assembly behaviour. Our results showed that the critical assembly concentration of Ket-L-VEVE was 0.32 mM in water to form various nanostructures which experienced from micelle, nanorod, nanofibre to nanoribbon. The morphology was influenced by multiple factors including molecular design, assembly time, pH and hydrogen bond inhibitor. On the basis of experimental results, we speculated the possible assembly mechanism of Ket-L-VEVE. The π-π stacking interaction between Ket molecules could serve as an anchor, and hydrogen bonded-induced β-sheets and hydrophilic/hydrophobic balance between L-VEVE peptide play structure-directing role in forming filament-like or nanoribbon morphology. This work provides a new sight to rationally design and precisely control the nanostructure of PDCs based on aromatic fragment.

pH-Triggered Peptide Self-Assembly for Targeting Imaging and Therapy toward Angiogenesis with Enhanced Signals

Mild acidic environment and angiogenesis are two typical characteristics of tumor. The specific response toward both lower pH and angiogenesis may enhance the targeting ability both for drug and diagnostic probe delivery. Herein, we present a kind of dual responding self-assembled nanotransformation material that is tumor angiogenesis targeting and pH triggered based on amphiphilic conjugation between peptides (STP) and aromatic molecules (tetraphenylethylene (TPE)). The morphology of the self-assembled peptide conjugates is responsibly changed from nanoparticles in neutral condition to nanofibers in acidic condition, which "turn on" the in vivo targeting imaging and accelerate the efficient drug delivery and in vivo therapy. On the basis of the well-controlled nanotransformation both in vitro and in vivo, we envisioned the successful demonstration of the responding materials would open a new avenue in turn on targeting imaging diagnostics and specific cancer therapeutics.

Bioactive Scaffolds for Regeneration of Cartilage and Subchondral Bone Interface

The cartilage lesion resulting from osteoarthritis (OA) always extends into subchondral bone. It is of great importance for simultaneous regeneration of two tissues of cartilage and subchondral bone. 3D-printed Sr₅(PO₄)₂SiO₄ (SPS) bioactive ceramic scaffolds may achieve the aim of regenerating both of cartilage and subchondral bone. We hypothesized that strontium (Sr) and silicon (Si) ions released from SPS scaffolds play a crucial role in osteochondral defect reconstruction.

Methods: SPS bioactive ceramic scaffolds were fabricated by a 3D-printing method. The SEM and ICPAES were used to investigate the physicochemical properties of SPS scaffolds. The proliferation and maturation of rabbit chondrocytes stimulated by SPS bioactive ceramics were measured in vitro. The stimulatory effect of SPS scaffolds for cartilage and subchondral bone regeneration was investigated in vivo.

Results: SPS scaffolds significantly stimulated chondrocyte proliferation, and SPS extracts distinctly enhanced the maturation of chondrocytes and preserved chondrocytes from OA. SPS scaffolds markedly promoted the regeneration of osteochondral defects. The complex interface microstructure between cartilage and subchondral bone was obviously reconstructed. The underlying mechanism may be related to Sr and Si ions stimulating cartilage regeneration by activating HIF pathway and promoting subchondral bone reconstruction through activating Wnt pathway, as well as preserving chondrocytes from OA via inducing autophagy and inhibiting hedgehog pathway.

Conclusion: Our findings suggest that SPS scaffolds can help osteochondral defect reconstruction and well reconstruct the complex interface between cartilage and subchondral bone, which represents a promising strategy for osteochondral defect regeneration.

Self-assembling prodrugs

Covalent modification of therapeutic compounds is a clinically proven strategy to devise prodrugs with enhanced treatment efficacies. This prodrug strategy relies on the modified drugs that possess advantageous pharmacokinetic properties and administration routes over their parent drug. Self-assembling prodrugs represent an emerging class of therapeutic agents capable of spontaneously associating into well-defined supramolecular nanostructures in aqueous solutions. The self-assembly of prodrugs expands the functional space of conventional prodrug design, affording a possible pathway to more effective therapies as the assembled nanostructure possesses distinct physicochemical properties and interaction potentials that can be tailored to specific administration routes and disease treatment. In this review, we will discuss the various types of self-assembling prodrugs in development, providing an overview of the methods used to control their structure and function and, ultimately, our perspective on their current and future potential.

Self-assembled RGD dehydropeptide hydrogels for drug delivery applications

Peptide-based self-assembled hydrogels have triggered remarkable research interest in recent years owing to their biocompatibility and biomimetic properties and responsiveness, which warrant many technological and biomedical applications. Dehydrodipeptides N-capped with naproxen emerged from our research as effective hydrogelators endowed with resistance to proteolysis. Dehydrodipeptide-based hydrogels are promising nanocarriers for drug delivery applications. In this work, we demonstrate that dehydrodipetide Npx-l-Ala-Z-ΔPhe-OH can be deployed as a minimalist hydrogelator module for synthesizing a gelating construct Npx-l-Ala-Z-ΔPhe-G-R-G-D-G-OH bearing a GRGDG adhesion motif. The self-assembly of the peptide construct and the drug delivery properties of the hydrogel were studied in this work. The peptide construct showed no toxicity towards a fibroblast cell line expressing the α_vβ₃ integrin. Docking studies suggest that the hydrogelator block does not interfere with the recognition of the RGD motif by the integrin receptor. The self-assembly seems to be directed by intermolecular naphthalene π-π stacking interactions, with the peptide backbone assuming a random coil conformation both in solution and in the gel phase. TEM and STEM imaging revealed that the hydrogel is made of entangled bundles of long thin fibres (width circa 23 nm). The hydrogel exhibits viscoelastic properties, thermo-reversibility and recovery after mechanical fluidization. FRET studies showed that curcumin incorporated into the hydrogel interacts non-covalently with the hydrogel fibrils. Delivery of curcumin from the hydrogel into Nile red loaded model membranes (SUVs) was demonstrated by FRET. Naproxen N-capped dehydrodipeptides are efficacious minimalist hydrogelator modules for obtaining hydrogels functionalized with peptide ligands for cell receptors. These hydrogels are potential nanocarriers for drug delivery.