Supramolecular Photoactivatable Anticancer Hydrogels

Novel aerogels based on supramolecular G-quadruplex assembly with intrinsic flame retardancy and thermal insulation

The construction of supramolecular aerogels still faces great challenges. Herein, we present a novel bio-based supramolecular aerogel derived from G-Quadruplex self-assembly of guanosine (G), boric acid (B) and sodium alginate (SA) and the obtained GBS aerogels exhibit superior flame-retardant and thermal insulating properties. The entire process involves environmentally friendly aqueous solvents and freeze-drying. Benefiting from the supramolecular self-assembly and interpenetrating dual network structures, GBS aerogels exhibit unique structures and sufficient self-supporting capabilities. The resulting GBS aerogels exhibit overall low densities (36.5-52.4 mg/cm3), and high porosities (>95 %). Moreover, GBS aerogels also illustrate excellent flame retardant and thermal insulating properties. With an oxygen index of 47.0-51.1 %, it can easily achieve a V-0 rating and low heat, smoke release during combustion. This work demonstrates the preparation of intrinsic flame-retardant aerogels derived from supramolecular self-assembly and dual cross-linking strategies, and is expected to provide an idea for the realization and application of novel supramolecular aerogel materials.

Current advance of nanotechnology in diagnosis and treatment for malignant tumors

Cancer remains a significant risk to human health. Nanomedicine is a new multidisciplinary field that is garnering a lot of interest and investigation. Nanomedicine shows great potential for cancer diagnosis and treatment. Specifically engineered nanoparticles can be employed as contrast agents in cancer diagnostics to enable high sensitivity and high-resolution tumor detection by imaging examinations. Novel approaches for tumor labeling and detection are also made possible by the use of nanoprobes and nanobiosensors. The achievement of targeted medication delivery in cancer therapy can be accomplished through the rational design and manufacture of nanodrug carriers. Nanoparticles have the capability to effectively transport medications or gene fragments to tumor tissues via passive or active targeting processes, thus enhancing treatment outcomes while minimizing harm to healthy tissues. Simultaneously, nanoparticles can be employed in the context of radiation sensitization and photothermal therapy to enhance the therapeutic efficacy of malignant tumors. This review presents a literature overview and summary of how nanotechnology is used in the diagnosis and treatment of malignant tumors. According to oncological diseases originating from different systems of the body and combining the pathophysiological features of cancers at different sites, we review the most recent developments in nanotechnology applications. Finally, we briefly discuss the prospects and challenges of nanotechnology in cancer.

Telmisartan loading thermosensitive hydrogel repairs gut epithelial barrier for alleviating inflammatory bowel disease

Inflammatory bowel disease (IBD) remains a global health concern with a complex and incompletely understood pathogenesis. In the course of IBD development, damage to intestinal epithelial cells and a reduction in the expression of tight junction (TJ) proteins compromise the integrity of the intestinal barrier, exacerbating inflammation. Notably, the renin-angiotensin system and angiotensin II receptor type 1 (AT1R) play a crucial role in regulating the pathological progression including vascular permeability, and immune microenvironment. Thus, Telmisartan (Tel), an AT1R inhibitor, loading thermosensitive hydrogel was constructed to investigate the potential of alleviating inflammatory bowel disease through rectal administration. The constructed hydrogel exhibits an advantageous property of rapid transformation from a solution to a gel state at 37°C, facilitating prolonged drug retention within the gut while mitigating irritation associated with rectal administration. Results indicate that Tel also exhibits a beneficial effect in ameliorating colon shortening, colon wall thickening, cup cell lacking, crypt disappearance, and inflammatory cell infiltration into the mucosa in colitis mice. Moreover, it significantly upregulates the expression of TJ proteins in colonic tissues thereby repairing the intestinal barrier damage and alleviating the ulcerative colitis (UC) disease process. In conclusion, Tel-loaded hydrogel demonstrates substantial promise as a potential treatment modality for IBD.

Cationic and amphiphilic peptide-based hydrogels with dual activities as anticancer and antibacterial agents

The emergence of peptide-based functional biomaterials is on the rise. To fulfil this purpose, a series of amphiphilic peptides, such as H2N-X-Met-Phe-C12H25, where X = L-lysine (CP1), X = L-histidine (CP2), and X = L-leucine (CP3), have been designed, synthesised, purified and fully characterised. Herein, we reported peptide-based supramolecular hydrogels with antibacterial and anticancer activities. An attempt has been made to investigate the antibacterial properties of these peptide-based hydrogels against Gram-positive (S. aureus and B. subtilis) and Gram-negative (E. coli and P. aeruginosa) bacteria. Investigations show that the L-lysine containing gelator, CP1, is active against both Gram-positive and Gram-negative bacteria and the L-histidine containing gelator, CP2, selectively inhibits the growth of Gram-negative bacteria. Interestingly, the L-leucine containing gelator, CP3, does not show any antibacterial properties. Moreover, the L-lysine containing gelator exhibits the best potency. Generation of reactive oxygen species (ROS) is a probable way to damage the bacterial membrane. To explore the cytotoxic properties and to determine the efficacy of the synthesized compounds in inhibiting cell viability, a comprehensive investigation was performed using three distinct cell lines: MDA-MB-231 (human triple-negative breast cancer), MDA-MB-468 (human triple-negative breast cancer) and HEK 293 (human embryonic kidney). Remarkably, the results of our study revealed a substantial cytotoxic impact of these peptide gelators on the MDA-MB-231 and MDA-MB-468 cell lines in comparison to the HEK 293 cells. Caspase 3/7 activity is the possible mechanistic path to determine the apoptotic rates of the cell lines. This finding emphasizes the promising potential of these peptide-based gelators in targeting and suppressing the growth of human triple negative breast cancer cells, while showing non-cytotoxicity towards non-cancerous HEK 293 cells. In a nutshell, these peptide-based materials are coming to light as next generation biomaterials.

A Guanosine-Derived Antitumor Supramolecular Prodrug

The prodrug strategy for its potential to enhance the pharmacokinetic and/or pharmacodynamic properties of drugs, especially chemotherapeutic agents, has been widely recognized as an important means to improve therapeutic efficiency. Irinotecan's active metabolite, 7-ethyl-10-hydroxycamptothecin (SN38), a borate derivative, was incorporated into a G-quadruplex hydrogel (GB-SN38) by the ingenious and simple approach. Drug release does not depend on carboxylesterase, thus bypassing the side effects caused by ineffective activation, but specifically responds to the ROS-overexpressed tumor microenvironment by oxidative hydrolysis of borate ester that reduces serious systemic toxicity from nonspecific biodistribution of SN38. Comprehensive spectroscopy was used to define the structural and physicochemical characteristics of the drug-loaded hydrogel. The GB-SN38 hydrogel's high level of biosafety and notable tumor-suppressive properties were proven in in vitro and in vivo tests.

Smart G-quadruplex hydrogels: From preparations to comprehensive applications

In recent years, the accelerated development of G-quadruplexes and hydrogels has driven the development of intelligent biomaterials. Based on the excellent biocompatibility and special biological functions of G-quadruplexes, and the hydrophilicity, high-water retention, high water content, flexibility and excellent biodegradability of hydrogels, G-quadruplex hydrogels are widely used in various fields by combining the dual advantages of G-quadruplexes and hydrogels. Here, we provide a systematic and comprehensive classification of G-quadruplex hydrogels in terms of preparation strategies and applications. This paper reveals how G-quadruplex hydrogels skillfully utilize the special biological functions of G-quadruplexes and the skeleton structure of hydrogels, and expounds its applications in the fields of biomedicine, biocatalysis, biosensing and biomaterials. In addition, we deeply analyze the challenges in preparation, applications, stability and safety of G-quadruplex hydrogels, as well as potential future development directions.

Programmable supramolecular chirality in non-equilibrium systems affording a multistate chiroptical switch

The dynamic regulation of supramolecular chirality in non-equilibrium systems can provide valuable insights into molecular self-assembly in living systems. Herein, we demonstrate the use of chemical fuels for regulating self-assembly pathway, which thereby controls the supramolecular chirality of assembly in non-equilibrium systems. Depending on the nature of different fuel acids, the system shows pathway-dependent non-equilibrium self-assembly, resulting in either dynamic self-assembly with transient supramolecular chirality or kinetically trapped self-assembly with inverse supramolecular chirality. More importantly, successive conducting of chemical-fueled process and thermal annealing process allows for the sequential programmability of the supramolecular chirality between four different chiral hydrogels, affording a new example of a multistate supramolecular chiroptical switch that can be recycled multiple times. The current finding sheds new light on the design of future supramolecular chiral materials, offering access to alternative self-assembly pathways and kinetically controlled non-equilibrium states.

Molecular dynamics study of low molecular weight gel forming salt-triggered dipeptide

Molecular dynamics simulation method was used to study the aggregation of Na and Ca salts in different concentrations of Naphthalene-dipeptide (2NapFF) solutions. The results show that high-valence Ca2+ triggers the formation of a gel at a certain dipeptide concentration, and the low-valence Na+ system follows the aggregation law of general surfactants. The results also show that hydrophobic and electrostatic forces are the main driving forces for the formation of dipeptide aggregates, and that hydrogen bonds do not play a major role in the formation of dipeptide solution aggregates. Hydrophobic and electrostatic effects are the main driving forces for the formation of gels in dipeptide solutions triggered by Ca2+. Electrostatic attraction drives Ca2+ to form a weak coordination with four oxygen atoms on two carboxyl groups, which causes the dipeptide molecules to form a gel with a branched network structure.

A simple method for fabricating drugs containing a cis-o-diol structure into guanosine-based supramolecular hydrogels for drug delivery

Supramolecular hydrogels are attractive biomaterials for local drug delivery owing to their excellent self-healing, injectable, biodegradable, and biocompatible properties. However, traditional drug-loading approaches based on non-covalent encapsulation and covalent bonding have shown problems such as rapid or difficult drug release, complex reaction processes, low reaction efficiency, and decreased drug activity. Therefore, there is a need to find a simple and efficient method to load drugs into hydrogels, which possess stable drug release ability without impairing drug efficacy. In this study, we introduce dynamic borate ester bonds via a simple one-pot method to load cis-o-diol-containing drugs into guanosine (G)-based supramolecular hydrogels. The experimental results confirm that the dynamic covalent borate ester bonds are formed based on the cis-o-diol groups of the drug and the G in these hydrogels. Meanwhile, the as-prepared G-based hydrogels not only possess self-healing properties and injectability but also have satisfactory biodegradability and biocompatibility. Additionally, the drug can be released from the G-based hydrogel according to the pH-responsive cleavage of the borate ester bonds without affecting drug activity. Overall, these results indicate that the simple one-pot method of utilizing the dynamic borate bond can provide a valuable reference for the design of hydrogel dosage forms.

Shear recovery and temperature stability of Ca2+ and Ag+ glycolipid fibrillar metallogels with unusual β-sheet-like domains

Low-molecular weight gelators (LMWGs) are small molecules (M_w < ∼1 kDa), which form self-assembled fibrillar network (SAFiN) hydrogels in water. A great majority of SAFiN gels are described by an entangled network of self-assembled fibers, in analogy to a polymer in a good solvent. Here, fibrillation of a biobased glycolipid bolaamphiphile is triggered by Ca²⁺ or Ag⁺ ions which are added to its diluted micellar phase. The resulting SAFiN, which forms a hydrogel above 0.5 wt%, has a "nano-fishnet" structure, characterized by a fibrous network of both entangled fibers and β-sheet-like rafts, generally observed for silk fibroin, actin hydrogels or mineral imogolite nanotubes, but generally not known for SAFiN. This work focuses on the strength of the SAFIN gels, their fast recovery after applying a mechanical stimulus (strain) and their unusual resistance to temperature, studied by coupling rheology to small angle X-ray scattering (rheo-SAXS) using synchrotron radiation. The Ca²⁺-based hydrogel maintains its properties up to 55 °C, while the Ag⁺-based gel shows a constant elastic modulus up to 70 °C, without the appearance of any gel-to-sol transition temperature. Furthermore, the glycolipid is obtained by fermentation from natural resources (glucose and rapeseed oil), thus showing that naturally engineered compounds can have unprecedented properties, when compared to the wide range of chemically derived amphiphiles.

Recent Developments in G-Quadruplex Binding Ligands and Specific Beacons on Smart Fluorescent Sensor for Targeting Metal Ions and Biological Analytes

The G-quadruplex structure is crucial in several biological processes, including DNA replication, transcription, and genomic maintenance. G-quadruplex-based fluorescent probes have recently gained popularity because of their ease of use, low cost, excellent selectivity, and sensitivity. This review summarizes the latest applications of G-quadruplex structures as detectors of genome-wide, enantioselective catalysts, disease therapeutics, promising drug targets, and smart fluorescence probes. In every section, sensing of G-quadruplex and employing G4 for the detection of other analytes were introduced, respectively. Since the discovery of the G-quadruplex structure, several studies have been conducted to investigate its conformations, biological potential, stability, reactivity, selectivity for chemical modification, and optical properties. The formation mechanism and advancements for detecting different metal ions (Na⁺, K⁺, Ag⁺, Tl⁺, Cu⁺/Cu²⁺, Hg²⁺, and Pb²⁺) and biomolecules (AMP, ATP, DNA/RNA, microRNA, thrombin, T4 PNK, RNase H, ALP, CEA, lipocalin 1, and UDG) using fluorescent sensors based on G-quadruplex modification, such as dye labels, artificial nucleobase moieties, dye complexes, intercalating dyes, and bioconjugated nanomaterials (AgNCs, GO, QDs, CDs, and MOF) is described herein. To investigate these extremely efficient responsive agents for diagnostic and therapeutic applications in medicine, fluorescence sensors based on G-quadruplexes have also been employed as a quantitative visualization technique.

The role of Platinum(IV)-based antitumor drugs and the anticancer immune response in medicinal inorganic chemistry. A systematic review from 2017 to 2022

Platinum-based antitumor drugs have been used in many types of tumors due to its broad antitumor spectrum in clinic. Encouraged by the cisplatin's (CDDP) worldwide success in cancer chemotherapy, the research in platinum-based antitumor drugs has evolved from traditional platinum drug to multi-ligand and multifunctional platinum prodrugs over half a century. With the rapid development of metal drugs and the anticancer immune response, challenges and opportunities in platinum drug research have been shifted from traditional platinum-based drugs to platinum-based hybrids and the direction of development is tending toward photodynamic therapy, nano-delivery therapy, drug combination, targeted therapy, diagnostic therapy, immune-combination therapy and tumor stem cell therapy. In this review, we first exhaustively overviewed the role of platinum-based antitumor prodrugs and the anticancer immune response in medicinal inorganic chemistry based on the special nanomaterials, the modification of specific ligands, and the multiple functions obtained that are beneficial for tumor therapy in the last five years. We also categorized them according to drug potency and function. There hasn't been a comprehensive evaluation of precursor platinum drugs in prior articles. And a multifarious approach to distinguish and detail the variety of alterations of platinum-based precursors in various valence states also hasn't been summarized. In addition, this review points out the main problems at the interface of chemistry, biology, and medicine from their action mechanisms for current platinum drug development, and provides up-to-date potential strategies from drug design perspectives to circumvent those drawbacks. And a promising idea is also enlightened for researchers in the development and discovery of platinum prodrugs.

NIR-light-controlled G-quadruplex hydrogel for synergistically enhancing photodynamic therapy via sustained delivery of metformin and catalase-like activity in breast cancer

Severely hypoxic condition of tumour represents a notable obstacle against the efficiency of photodynamic therapy (PDT). While mitochondria targeted therapy by metformin has been considered as a promising strategy for reducing oxygen consumption in tumours, its low treatment sensitivity, short half-life and narrow absorption window in vivo remain the intractable challenges. In this report, 5′-guanosine monophosphate (5′GMP), indocyanine green (ICG), hemin and metformin, were combined to construct a smart G-quadruplex (G4) hydrogel named HMI@GEL for breast cancer (BC) treatment. Benefiting from the photothermal (PTT) effect of ICG, HMI@GEL exhibited excellent characteristics of NIR-light-triggered and persistent drug delivery to maintain high intratumoral concentration of metformin. Furthermore, drug loading concentration of metformin reached an amazing 300 ​mg ​mL⁻¹ in HMI@GEL. To our knowledge, it might be the highest loading efficiency in the reported literatures. With the combination of catalase-mimicking Hemin@mil88, metformin could inhibit tumour mitochondrial respiratory significantly, which sequentially permitted in situ efficient oxygen generation. Remarkable apoptosis and necrosis were achieved by the combination of PTT and synergistically enhanced PDT as well as the activated tumour immunotherapy. Collectively, the HMI@GEL in situ injectable platform showed a promising strategy for enhanced PDT by metformin, and opened new perspectives for treating BC versatilely.

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A NIR-light-controlled G-quadruplex hydrogel HMI@GEL loading metformin was prepared for precision breast cancer therapy.

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The extremely high drug loading capacity (300 ​mg ​mL⁻¹) and persistent delivery of metformin was realized for the first time.

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The combination of catalase-mimicking Hemin@mil88 and metformin dual enhanced intracellular ROS generation.

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The tumour immune microenvironment was dramatically reshaped by synthetic photodynamic/photothermal therapy.

Rutin-Loaded Stimuli-Responsive Hydrogel for Anti-Inflammation

An active flavonoid compound rutin was incorporated into a guanosine phenylborate hydrogel (GBR) by a stimuli-responsive borate ester linkage for the treatment of inflammatory bowel disease (IBD). The components and morphology of the drug delivery system were characterized by NMR, UV-vis spectroscopy, and AFM. Rheological measurements revealed the required injectability and self-healing ability, which contributed to its application in rectal administration. The cell assays proved the excellent compatibility and safety of the system, and a possible pathway to form multicellular aggregates. In vitro drug-release studies showed that the hydrogel exhibited good stability in physiological medium, and the drug was almost completely released (more than 90 wt % after 24 h of incubation) in acidic pH and excessive ROS-containing medium, realizing the dual-responsive release of pH/ROS. In vivo activities of the GBR hydrogel showed higher therapeutic efficacy than free rutin in a colitis mice model, and it could significantly inhibit overexpressed inflammatory cytokines, including TNF-α and IL-6. Degradation studies of the hydrogel provided further evidence for the safety of its in vivo application. The work provided a simple strategy to prepare a G-quadruplex drug carrier, which was expected to achieve multi-drug delivery.

A guanosine-based hydrogel integrating photothermal effect of PDAAuNPs through dynamic borate bond for photothermal therapy of cancer

Photothermal therapy (PTT) has drawn extensive attention owing to its noninvasive and great tissue penetration depth. However, the physical encapsulation of photothermal agents may lead to their rapid release. Dual-functional hydrogel systems that integrate functions and carriers can potentially solve this problem. In this work, we successfully developed a dual-functional guanosine(G)-based hydrogel integrating the photothermal effect and localized delivery by introducing dynamic borate ester utilizing the photothermal property of PDA-AuNPs and the self-assembly ability of G. Both in vitro and in vivo results confirmed that the GBPA hydrogel not only exhibited excellent photothermal toxicity, stability, injectability, and biocompatibility, but also possessed high photothermal antitumor activity. These results suggested that the GBPA hydrogel could be used as a dual-functional hydrogel integrating photothermal effect and localized delivery in one system, which would possibly provide a new opportunity for the design of new dual-functional hydrogels for highly efficient cancer therapy.

Polyphenol-based hydrogels: Pyramid evolution from crosslinked structures to biomedical applications and the reverse design

As a kind of nature-derived bioactive materials, polyphenol-based hydrogels possess many unique and outstanding properties such as adhesion, toughness, and self-healing due to their specific crosslinking structures, which have been widely used in biomedical fields including wound healing, antitumor, treatment of motor system injury, digestive system disease, oculopathy, and bioelectronics. In this review, starting with the classification of common polyphenol-based hydrogels, the pyramid evolution process of polyphenol-based hydrogels from crosslinking structures to derived properties and then to biomedical applications is elaborated, as well as the efficient reverse design considerations of polyphenol-based hydrogel systems are proposed. Finally, the existing problems and development prospects of these hydrogel materials are discussed. It is hoped that the unique perspective of the review can promote further innovation and breakthroughs of polyphenol-based hydrogels in the future.

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Polyphenol-based hydrogels combine advantages of polyphenols with common hydrogels.

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Cognition of such hydrogels underwent from structures to properties to applications.

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Various crosslinked structures of such hydrogels can derive outstanding properties.

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Such hydrogels can be widely used in biomedicine due to the outstanding properties.

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Reverse design thought from applications to properties to structures is promising.

Chiral rhodium(III)-azobenzene complexes as photoswitchable DNA molecular locks

Chiral rhodium(III)-azobenzene complexes which are able to intercalate into DNA were developed. Upon light exposure, the azobenzene moiety of the metal complex can photoisomerize from the trans- into the cis-form...

Metal substrate catalysis in the confined space for platinum drug delivery

Catalysis-based approaches for the activation of anticancer agents hold considerable promise. These principally rely on the use of metal catalysts capable of deprotecting inactive precursors of organic drugs or transforming key biomolecules available in the cellular environment. Nevertheless, the efficiency of most of the schemes described so far is rather low, limiting the benefits of catalytic amplification as strategy for controlling the therapeutic effects of anticancer compounds. In the work presented here, we show that flavin reactivity within a hydrogel matrix provides a viable solution for the efficient catalytic activation and delivery of cisplatin, a worldwide clinically-approved inorganic chemotherapy agent. This is achieved by ionically adsorbing a flavin catalyst and a Pt(iv) prodrug as substrate into porous amino-functionalized agarose beads. The hydrogel chassis supplies high local concentrations of electron donating groups/molecules in the surrounding of the catalyst, ultimately boosting substrate conversion rates (TOF >200 min-1) and enabling controlled liberation of the drug by light or chemical stimuli. Overall, this approach can afford platforms for the efficient delivery of platinum drugs as demonstrated herein by using a transdermal diffusion model simulating the human skin.

Single-Cell Chemistry of Photoactivatable Platinum Anticancer Complexes

The Pt(IV) prodrug trans, trans, trans-[Pt(pyridine)2(N3)2(OH)2] (Pt1) and its coumarin derivative trans, trans, trans-[Pt(pyridine)2(N3)2(OH)(coumarin-3-carboxylate)] (Pt2) are promising agents for photoactivated chemotherapy. These complexes are inert in the dark but release Pt(II) species and radicals upon visible light irradiation, resulting in photocytotoxicity toward cancer cells. Here, we have used synchrotron techniques to investigate the in-cell behavior of these prodrugs and visualize, for the first time, changes in cellular morphology and Pt localization upon treatment with and without light irradiation. We show that photoactivation of Pt2 induces remarkable cellular damage with extreme alterations to multiple cellular components, including formation of vacuoles, while also significantly increasing the cellular accumulation of Pt species compared to dark conditions. X-ray absorption near-edge structure (XANES) measurements in cells treated with Pt2 indicate only partial reduction of the prodrug upon irradiation, highlighting that phototoxicity in cancer cells may involve not only Pt(II) photoproducts but also photoexcited Pt(IV) species.

A Carbonic Anhydrase IX (CAIX)-Anchored Rhenium(I) Photosensitizer Evokes Pyroptosis for Enhanced Anti-Tumor Immunity

An ideal cancer treatment should not only destroy primary tumors but also improve the immunogenicity of the tumor microenvironment to achieve a satisfactory anti-tumor immune effect. We designed a carbonic anhydrase IX (CAIX)-anchored rhenium(I) photosensitizer, named CA-Re, that not only performs type-I and type-II photodynamic therapy (PDT) with high efficiency under hypoxia (nanomolar-level phototoxicity), but also evokes gasdermin D (GSDMD) mediated pyroptotic cell death to effectively stimulate tumor immunogenicity. CA-Re could disrupt and self-report the loss of membrane integrity simultaneously. This promoted the maturation and antigen-presenting ability of dendritic cells (DCs), and fully activated T cells dependent adaptive immune response in vivo, eventually eliminating distant tumors at the same time as destroying primary tumors. To the best of our knowledge, CA-Re is the first metal complex-based pyroptosis inducer.

Heterocycle-modified 2'-Deoxyguanosine Nucleolipid Analogs Stabilize Guanosine Gels and Self-assemble to Form Green Fluorescent Gels

Nucleoside-lipid conjugates are very useful supramolecular building blocks to construct self-assembled architectures suited for biomedical and material applications. Such nucleoside derivatives can be further synthetically manipulated to endow additional functionalities that could augment the assembling process and impart interesting properties. Here, we report the design, synthesis and self-assembling process of multifunctional supramolecular nucleolipid synthons containing an environment-sensitive fluorescent guanine. The amphiphilic synthons are composed of an 8-(2-(benzofuran-2-yl)vinyl)-guanine core and alkyl chains attached to 3'-O and 5'-O-positions of 2'-deoxyguanosine. The 2-(benzofuran-2-yl)vinyl (BFV) moiety attached at the C8 position of the nucleobase adopted a syn conformation about the glycosidic bond, which facilitated the self-assembly process through the formation of a G-tetrad as the basic unit. While 3',5'-diacylated BFV-modified dG analog stabilized the guanosine hydrogel by hampering the crystallization process and imparted fluorescence, BFV-modified dGs containing longer alkyl chains formed a green fluorescent organogel, which transformed into a yellow fluorescent gel in the presence of a complementary non-fluorescent cytidine nucleolipid. The ability of the dG analog containing short alkyl chains to modulate the mechanical property of a gel, and interesting fluorescence properties and self-assembling behavior exhibited by the dG analogs containing long alkyl chains in response to heat and complementary base underscore the potential use of these new supramolecular synthons in material applications.

Palmitic acid sophorolipid biosurfactant: from self-assembled fibrillar network (SAFiN) to hydrogels with fast recovery

Nanofibres are an interesting phase into which amphiphilic molecules can self-assemble. Described for a large number of synthetic lipids, they were seldom reported for natural lipids like microbial amphiphiles, known as biosurfactants. In this work, we show that the palmitic acid congener of sophorolipids (SLC16:0), one of the most studied families of biosurfactants, spontaneously forms a self-assembled fibre network (SAFiN) at pH below 6 through a pH jump process. pH-resolved in situ small-angle X-ray scattering (SAXS) shows a continuous micelle-to-fibre transition, characterized by an enhanced core-shell contrast between pH 9 and pH 7 and micellar fusion into a flat membrane between pH 7 and pH 6, approximately. Below pH 6, homogeneous, infinitely long nanofibres form by peeling off the membranes. Eventually, the nanofibre network spontaneously forms a thixotropic hydrogel with fast recovery rates after applying an oscillatory strain amplitude out of the linear viscoelastic regime: after being submitted to strain amplitudes during 5 min, the hydrogel recovers about 80% and 100% of its initial elastic modulus after, respectively, 20 s and 10 min. Finally, the strength of the hydrogel depends on the medium's final pH, with an elastic modulus fivefold higher at pH 3 than at pH 6. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)'.

Unexpected photoactivation pathways in a folate-receptor-targeted trans-diazido Pt(IV) anticancer pro-drug

A conjugate between a photoactive trans-diazido Pt(iv) pro-drug, trans,trans,trans-[Pt(N3)2(OH)2(py)2], and folic acid has been synthesized and fully characterized by high resolution ESI-MS, NMR and UV-vis spectroscopy. Photoactivation of the Pt-folate conjugate with visible light confirmed the generation of cytotoxic Pt(ii) species capable of binding to guanine nucleobases. Importantly, photoreduction of the Pt(iv) complex triggered the photodecomposition of the folate vector into a p-aminobenzoate-containing fragment and several pterin derivatives, including 6-formylpterin. Besides exhibiting high dark stability in physiological-like conditions, the Pt-folate conjugate was ca. 2× more photocytotoxic towards MCF-7 breast cancer cell line than its parent Pt(iv) complex with a high photoselectivity index (PI > 6.9). The higher photocytotoxicity of the conjugate may be a consequence of its higher cellular accumulation and of the generation of a set of different cytotoxic species, including Pt(ii) photoproducts and several pterin derivatives, which are known to generate ROS.

Self-healing mechanism and bioelectrochemical interface properties of core-shell guanosine-borate hydrogels

The self-healing mechanism and bioelectrochemical interface properties of supramolecular gels have been rarely explored. In this context, we propose a constitutive "fibril-reorganization" model to reveal the self-healing mechanism of a series of core-shell structured guanosine-borate (GB) hydrogels and emphasize that interfibrillar interactions at the supramolecular polymer scale (G-quadruplex nanowires) drive the self-healing process of GB hydrogels. Structure-electrochemical sensing performance studies reveal that GB hydrogel nanofibers with relatively strong biomolecular affinity such as -SH modified GB hydrogel (GB-SH) show a high sensitivity of response and low limit of detection for tumour marker alpha-fetoprotein sensing (AFP; 0.076 pg mL^-1). Guanosine/ferroceneboronic acid (GB-Fc) hydrogel nanofibers with superior conductivity and redox activity display the widest linear detection range for AFP (0.0005-100 ng mL^-1). Structure-property correlations of GB hydrogels provide useful insight for the future design of advanced self-healing materials and electrochemical biosensors.

An intensive and glow-type chemiluminescence of luminol-embedded, guanosine-derived hydrogel

In this paper, an intensive and glow-type chemiluminescence (CL) hydrogel was prepared by simultaneous incorporation of chemiluminescence reagent (luminol) and catalytic cofactor (hemin) into the scaffold of guanosine-derived hydrogel. The self-assembled hydrogel consisted of K⁺ stabilized hemin/G-quartet structures, showing significant enzyme-like activity to H₂O₂-mediated oxidation of luminol. After adding H₂O₂ into the hydrogel, blue light visible to naked eyes would come into being and last for over 8 h. The lasting-time CL emission of hydrogel was achieved due to a mechanism of slow-diffusion-controlled heterogeneous catalysis. Moreover, this self-assembled hydrogel performed a good response to H₂O₂ and the CL emission images could be recorded by smartphone. The hydrogel could remain excellent lifetime stability for months and the stable, enhanced and glow-type CL emission could improve the reliability and precision of CL detection, which has a promising application in cold light source and H₂O₂ detection of real biological samples.

Supramolecular cancer nanotheranostics

Among the many challenges in medicine, the treatment and cure of cancer remains an outstanding goal given the complexity and diversity of the disease. Nanotheranostics, the integration of therapy and diagnosis in nanoformulations, is the next generation of personalized medicine to meet the challenges in precise cancer diagnosis, rational management and effective therapy, aiming to significantly increase the survival rate and improve the life quality of cancer patients. Different from most conventional platforms with unsatisfactory theranostic capabilities, supramolecular cancer nanotheranostics have unparalleled advantages in early-stage diagnosis and personal therapy, showing promising potential in clinical translations and applications. In this review, we summarize the progress of supramolecular cancer nanotheranostics and provide guidance for designing new targeted supramolecular theranostic agents. Based on extensive state-of-the-art research, our review will provide the existing and new researchers a foundation from which to advance supramolecular cancer nanotheranostics and promote translationally clinical applications.

BODIPY-linked cis-dichlorido zinc(ii) conjugates: the strategic design of organelle-specific next-generation theranostic photosensitizers

Cis-dichlorido Zn(ii)–BODIPY-based smart theranostic photosensitizers, as alternatives to Zn-porphyrins/phthalocyanines, show mitochondrion-targeted and imaging guided type-II photodynamic therapeutic activity.

Advances of hydrogel dressings in diabetic wounds

The hydrogel dressings with various functions for diabetic wound treatment.

Self-assembled guanosine-hydrogels for drug-delivery application: Structural and mechanical characterization, methylene blue loading and controlled release

It is known that guanosine derivatives (G) self-assemble in water forming long, flexible, and interacting aggregates (the so-called G-quadruplexes): by modulating the quadruplex charges, e.g. simply using a mixture of guanosine 5'-monophosphate (GMP) and guanosine (Gua), multi-responsive, self-healing hydrogels can be obtained. In this paper, the potential application of G-hydrogels as drug delivery systems has been assessed. Hydrogels were prepared at different Gua:GMP molar ratios. The photosensitizer Methylene Blue and the pro-apoptotic protein cytochrome C were used as cargo molecules. Small angle x-ray scattering and atomic force microscopy experiments confirmed the presence of G-quadruplexes disposed in swollen matrices with different mesh-sizes. Rheology measurements showed that the Gua:GMP molar ratio leads to specific drug release mechanisms, as the gel strength is finely tuned by electrostatic repulsion and van der Waals attraction between G-quadruplexes. Noteworthy, the gel cohesion and the drug release were pH responsive. Swelling, self-healing and cell viability features were also investigated: the results qualify the Gua:GMP hydrogel as an excellent biomaterial that can entrap and deliver key biomolecules in a sustained and responsive release manner.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Selective functionalization at N2-position of guanine in oligonucleotides via reductive amination

Chemo- and site-specific modifications in oligonucleotides have wide applicability as mechanistic probes in chemical biology. However, methods that label specific sites in nucleic acids are scarce, especially for labeling DNA/RNA from biological or enzymatic sources rather than synthetic ones. Here we have employed a classical reaction, reductive amination, to selectively functionalize the N²-amine of guanosine and 2'-deoxyguanosine monophosphate (GMP/dGMP). This method specifically modifies guanine in DNA and RNA oligonucleotides, while leaving the other nucleobases unaffected. Using this approach, we have successfully incorporated a reactive handle chemoselectively into nucleic acids for further functionalization and downstream applications.

Construction of Supramolecular Organogel with Circularly Polarized Luminescence by Self-Assembled Guanosine Octamer

Gel formation using guanosine self-assembly is an important process in supramolecular chemistry. Here, we report the stepwise construction of circularly polarized luminescent supramolecular organogels from self-assembled guanosine quadruplexes. A lipophilic guanosine derivative (aldG) is designed and synthesized for the formation of a well-defined G8-octamer. The diamine linkers are used to connect G8-octamer units by imine formation to facilitate the construction of the supramolecular gel networks. 1H NMR experiments show that the pre-assembled aldG8-octamer remains intact and is crucial for transparent and stiff organogel formation. With extended conjugation, the aldG organogels exhibit strong green fluorescence emission and circularly polarized properties without the assistance of any external fluorescent dyes, suggesting an alternative approach to construct molecular probes for biological and material applications.

A guanosine-based 2-formylphenylborate ester hydrogel with high selectivity to K+ ions

Guanosine-based supramolecular hydrogels are particularly of interest for biomaterial and biomedical purposes, as they are generally biocompatible and stimuli-responsive. We found a strong and long-life transparent hydrogel made by mixing guanosine (G) with 1 equiv. of 2-formylbenzeneboronic acid (2FPB) and KOH. Alkali cations can assist the stacking of individual G-quartet to give extended nanowires, but only K⁺ ion induces the formation of a stable and self-supporting network hydrogel for a couple of months. Data from variable temperature NMR indicated that guanosine 2-formylbenzeneborate ester and G are the key components of the self-assembly. Further, G-2FPB-K⁺ hydrogel solution can induce berberine (BBR) fluorescence, showing high selectivity to K⁺ ion and anti-ion interference capability. A good linear relationship between fluorescent intensity and K⁺ concentration allowed us to directly detect K⁺ levels in human blood serum.

A new self-assembling system prepared from guanosine and 2-formylbenzeneboronic acid showed a high selectivity to potassium ions and has a fluorescent enhancement effect on berberine, which can be used for serum potassium detection.

Self-assembly of novel Fmoc-cardanol compounds into hydrogels - analysis based on rheological, structural and thermal properties

Hydrogels of low molecular weight molecules are particularly appealing for various biomedical applications such as drug delivery, tissue engineering, and antitumor therapy due to their excellent biocompatibility, biodegradability, and easy availability. Fmoc-peptide hydrogels form an essential category of these hydrogels. Herein we report a new class of Fmoc hydrogels in which cardanol (3-pentadecyl phenol (PDP)) is covalently linked with fluorenylmethyloxycarbonyl group. Cardanol is a plant-based renewable raw material, readily obtained from Cashew Nut Shell Liquid (CNSL). The long aliphatic chain of pentadecyl phenol helps in bringing a structural incompatibility and generates different nanostructures such as nanospheres, nanotapes, and nanofibers depending on Fmoc substitution and the solvents used. Stable hydrogels were formed from Fmoc-PDP in DMSO/H2O, and the critical aggregation concentration (CAC) and critical gelation concentration (CGC) were determined. The role of non-covalent forces such as hydrogen-bonding, hydrophobicity, and π-π stacking interactions in governing self-assembly to hydrogel formation was studied for Fmoc, DiFmoc and Boc groups attached to PDP. The thermal properties were analyzed, and smectic and nematic phases were identified for the molecules depending on the substitutions involved. Overall the study supports the mechanisms of aggregation and gelation in novel Fmoc-cardanol derivatives.

Supramolecular combination chemotherapy: a pH-responsive co-encapsulation drug delivery system

Most cancer chemotherapy regimens rely on the use of two or more chemotherapeutic agents. However, achieving the best possible dosing of the individual drugs can be challenging due to differences in metabolism, uptake, and clearance among other factors. Here we describe a supramolecular strategy for achieving drug delivery in which the loading ratio of two active components is easily defined. Specifically, we report the formation of aggregates comprised of self-assembled amphiphiles between carboxylatopillar[6]arene (CP6A) and an oxaliplatin (OX)-type Pt(iv) prodrug (PtC10). The association constant (K a) for the underlying host-guest interaction at pH 7.4 ((1.16 ± 0.03) × 104 M-1) is an order of magnitude higher than at pH 5.0 ((1.73 ± 0.15) × 103 M-1). A second chemotherapeutic, doxorubicin (DOX), may be encapsulated in the resulting vesicles (PtC10⊂CP6A) to give a supramolecular combination chemotherapeutic system DOX@PtC10⊂CP6A. Drug release studies served to confirm that PtC10 and DOX are released in acidic environments. Support for a synergistic antiproliferative effect relative to PtC10 + DOX came from cellular studies of DOX@PtC10⊂CP6A using the human liver hepatocellular carcinoma (HepG-2) cell line. In vivo studies revealed that DOX@PtC10⊂CP6A is not only able to retard tumor growth efficiently but also reduce drug-related toxic side effects in BALB/c nude mice bearing HepG-2 subcutaneous tumor xenografts. These favorable findings are attributed to the formation of a ternary complex that benefits from an enhanced permeability and retention (EPR) effect in vivo while allowing for the pH-based release of PtC10 and DOX at the tumor site.

Oxidation of 8-thioguanosine gives redox-responsive hydrogels and reveals intermediates in a desulfurization pathway

A disulfide made by oxidation of 8-thioguanosine is a supergelator. The hydrogels are redox-responsive, as they disassemble upon either reduction or oxidation of the S-S bond. We also identified this disulfide, and 2 other compounds, as intermediates in oxidative desulfurization of 8-thioG to guanosine.

Fabrication of self-healing hydrogel from quaternized N-[3(dimethylamino)propyl]methacrylamide copolymer for antimicrobial and drug release applications

Self-healing hydrogels have attracted great attention in recent years because of their wide application in bioscience and biotechnology. In this study, P(DMAPMA-stat-DAA) were synthesized by Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and quaternized to import antimicrobial properties. Then quaternized P(DMAPMA-stat-DAA) was used to prepare hydrogel containing acylhydrazone groups with Polyethylene oxide (PEO) diacylhydrazide as a cross-linking agent. The acylhydrazone groups imparted a variety of properties, including group responsiveness and self-healing properties to the hydrogel. At the same time, the quaternary ammonium endowed the hydrogel with the antimicrobial property. The mechanical property, self-healing properties, and antimicrobial property of hydrogels were investigated intensively. Results showed hydrogels formed in neutral conditions, and the luminescent property was introduced with PEO₂₃ dinaphthhydrazide (DNH) cross-linking. The hydrogels showed a controlled pH-sensitive DOX·HC l and Ovalbumin (OVA) release profile. In addition, the hydrogel showed the antimicrobial property and may have important applications in the biomedical field in the near future.

Guanosine Assembly Enabled Gold Nanorods with Dual Thermo- and Photoswitchable Plasmonic Chiroptical Activity

Noble metal nanostructures with plasmonic circular dichroism (PCD) have attracted interest, and a modulation of PCD is of great importance for their potential applications. Herein, we propose a supramolecular strategy for achieving dual thermal and photoswitchable PCD. When guanosine (G), deoxyguanosine (dG), and boric acid modified achiral gold nanorods (GNRs) were coassembled into a hydrogel, hybrid nanofibers with PCD were produced. When the hydrogel was heated, the nanofiber was disassembled and the PCD disappeared. As the hydrogel was thermally reversible, a thermo-controlled PCD could be realized. The hybrid hydrogel also showed photoswitchable PCD. When the gel was irradiated with an IR laser, the PCD disappeared. It can be restored by being placed at room temperature. Moreover, the hybrid gel was selectively responsive to the circularly polarized light (CPL). For (G/dG)-GNR hybrid assemblies, the R-CPL irradiation showed photothermal efficiency higher than that of L-CPL, which made it useful for an IR-irradiation-controlled release of drug molecules.

Metal ions confinement defines the architecture of G-quartet, G-quadruplex fibrils and their assembly into nematic tactoids

G-quadruplex, assembled from a square array of guanine (G) molecules, is an important structure with crucial biological roles in vivo but also a versatile template for ordered functional materials. Although the understanding of G-quadruplex structures is the focus of numerous studies, little is known regarding the control of G-quartet stacking modes and the spontaneous orientation of G-quadruplex fibrils. Here, the effects of different metal ions and their concentrations on stacking modes of G-quartets are elucidated. Monovalent cations (typically K+) facilitate the formation of G-quadruplex hydrogels with both heteropolar and homopolar stacking modes, showing weak mechanical strength. In contrast, divalent metal ions (Ca2+, Sr2+, and Ba2+) at given concentrations can control G-quartet stacking modes and increase the mechanical rigidity of the resulting hydrogels through ionic bridge effects between divalent ions and borate. We show that for Ca2+ and Ba2+ at suitable concentrations, the assembly of G-quadruplexes results in the establishment of a mesoscopic chirality of the fibrils with a regular left-handed twist. Finally, we report the discovery of nematic tactoids self-assembled from G-quadruplex fibrils characterized by homeotropic fibril alignment with respect to the interface. We use the Frank-Oseen elastic energy and the Rapini-Papoular anisotropic surface energy to rationalize two different configurations of the tactoids. These results deepen our understanding of G-quadruplex structures and G-quadruplex fibrils, paving the way for their use in self-assembly and biomaterials.

Engineered Dynamic Boronate Ester-Mediated Self-Healable Biocompatible G-Quadruplex Hydrogels for Sustained Release of Vitamins

Injectable, self-healable, and biocompatible dynamic hydrogels prepared from the molecular self-assembly and reversible covalent bond formation of low-molecular-weight hydrogelators are increasing in the field of drug delivery. Herein, we report the formation of G-quadruplex hydrogels via the multicomponent self-assembly and reversible bond formation between guanosine (G) and 1-naphthaleneboronic acid in the presence of the monovalent cation K⁺. The cation-templated stacking interaction of G4 quartets and the formation of dynamic cyclic boronate esters are responsible for the construction of dynamic G-quadruplex assembly. The in situ-synthesized dynamic cyclic boronate esters are well characterized by ¹¹B nuclear magnetic resonance and Fourier transform infrared spectroscopy methods. The formation and morphology of the G-quadruplex hydrogel are well supported by several spectroscopic and microscopic techniques. The injectability and self-healing ability of the G-quadruplex hydrogel are also investigated. The in vivo cytotoxicity of the G-quadruplex hydrogel is extensively evaluated over different cell lines (HeLa, MCF-7, and HEK293) to observe the biostability and broad-spectrum biocompatibility of the hydrogel. Further, this injectable, biocompatible G-quadruplex hydrogel has been used for encapsulation and sustained release of two important vitamins (B₂ and B₁₂) over 40 h at physiological pH (7.46) and temperature (37 °C) without the influence of any external stimuli.

Guanosine-Based Self-Assembly as an Enantioselective Catalyst Scaffold

A self-assembled G-quadruplex formed by guanosine and borate as the chiral scaffold was used to catalyze the asymmetric Friedel-Crafts reaction in water. Catalysis, depending on the self-assembly of guanosine and borate into a fibrillar structure in the presence of Cu²⁺ ions, can be modulated by the assembly concentration, temperature, and amount of Cu²⁺ ions. Detailed spectral experiments proved that the guanosine-based assembly in solution was responsible for the enantioselective catalysis, rather than small-molecule species. Some of the similar G-quartet assemblies were unable to promote the asymmetric reaction, implying unique properties of the current system, including excellent lifetime stability and supramolecular chiral structures. This work provided the first example of the self-assembled G-quadruplex achieving enantioselective catalysis and some perspective to better understand the design of nucleoside-based self-assemblies for an enantioselective reaction. In view of guanosine as a building block, these findings may be applied to discuss the prebiotic chiral catalyst preceded ribozymes.

New Designs for Phototherapeutic Transition Metal Complexes

In this Minireview, we highlight recent advances in the design of transition metal complexes for photodynamic therapy (PDT) and photoactivated chemotherapy (PACT), and discuss the challenges and opportunities for the translation of such agents into clinical use. New designs for light-activated transition metal complexes offer photoactivatable prodrugs with novel targeted mechanisms of action. Light irradiation can provide spatial and temporal control of drug activation, increasing selectivity and reducing side-effects. The photophysical and photochemical properties of transition metal complexes can be controlled by the appropriate choice of the metal, its oxidation state, the number and types of ligands, and the coordination geometry.

The development of isoguanosine: from discovery, synthesis, and modification to supramolecular structures and potential applications

First systematical review of isoguanosine, an unnatural base, as an isomer of guanosine shows significant differences in diverse properties.