Nucleopeptide-Coupled Injectable Bioconjugated Guanosine-Quadruplex Hydrogel with Inherent Antibacterial Activity

The multicomponent reaction-directed self-assembled hydrogels offer the opportunities to fabricate materials with ubiquitous properties which sometimes are not possible to generate from single components. Therefore, multicomponent-derived hydrogels have enormous applications in biomedical fields, and the number of such systems is increasing day by day. Herein, the multicomponent self-assembly techniques have been employed to develop a biomimetic low-molecular-weight G-quadruplex hydrogel under physiological conditions. The bioconjugation of guanosine, 4-formylphenylboronic acid, and cytosine-functionalized nucleopeptide (NP) is important to generate the multicomponent self-assembled dynamic imino-boronate ester-mediated bioconjugated G-quadruplex hydrogels. Using thioflavin T fluorescence assay, powder X-ray diffraction, and circular dichroism spectroscopic techniques, we confirm the existence of a G-quartet-like structure as the key parameter for the formation of nanofibrillar hydrogels. The multicomponent self-assembled G-quadruplex hydrogel possesses excellent inherent antibacterial activity against a broad range of bacterial species. The in vitro cytocompatibility of the synthesized hydrogel was evaluated on MCF-7 and HEK 293T cell lines to study the biocompatibility of the hydrogel. The proposed injectable, biocompatible, and NP-coupled G-quadruplex hydrogel with inherent antibacterial efficiency holds promising importance to prevent localized bacterial infections.

Current Knowledge on Biomaterials for Orthopedic Applications Modified to Reduce Bacterial Adhesive Ability

A significant challenge in orthopedics is the design of biomaterial devices that are able to perform biological functions by substituting or repairing various tissues and controlling bone repair when required. This review presents an overview of the current state of our recent research into biomaterial modifications to reduce bacterial adhesive ability, compared with previous reviews and excellent research papers, but it is not intended to be exhaustive. In particular, we investigated biomaterials for replacement, such as metallic materials (titanium and titanium alloys) and polymers (ultra-high-molecular-weight polyethylene), and biomaterials for regeneration, such as poly(ε-caprolactone) and calcium phosphates as composites. Biomaterials have been designed, developed, and characterized to define surface/bulk features; they have also been subjected to bacterial adhesion assays to verify their potential capability to counteract infections. The addition of metal ions (e.g., silver), natural antimicrobial compounds (e.g., essential oils), or antioxidant agents (e.g., vitamin E) to different biomaterials conferred strong antibacterial properties and anti-adhesive features, improving their capability to counteract prosthetic joint infections and biofilm formation, which are important issues in orthopedic surgery. The complexity of biological materials is still far from being reached by materials science through the development of sophisticated biomaterials. However, close interdisciplinary work by materials scientists, engineers, microbiologists, chemists, physicists, and orthopedic surgeons is indeed necessary to modify the structures of biomaterials in order to achieve implant integration and tissue regeneration while avoiding microbial contamination.

Chirality-influenced antibacterial activity of methylthiazole- and thiadiazole-based supramolecular biocompatible hydrogels

Chiral stereochemistry is a unique and fundamental strategy that determines the interaction of bacteria cells with chiral biomolecules and stereochemical surfaces. The interaction between bacteria and material surface (molecular chirality or supramolecular chirality) plays a significant role in modulating antibacterial performance. Herein, we developed inherent chiral antibacterial hydrogels by modifying the carboxyl groups of our previously reported supramolecular gelator (LPF-left handed phenylalanine gelator and DPF- right handed phenylalanine gelator) with 2-amino-5-methylthiazole (MTZ) and 5-amino-1,3,4-thiadiazole-2- thiol (TDZ). The new L/D-gelator molecules initiate self-assembly to form hydrogels through non-covalent interactions (Hydrogen bonding and π-π interactions) verified by FTIR and CD spectroscopy. Morphological studies of the xerogels revealed left and right-handed chiral nanofibers for the gelators' L-form and D-form, respectively. The resulting hydrogels exhibited inherent antibacterial activity against Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria, with TDZ hydrogels showing more significant antibacterial activity than MTZ hydrogels. Interestingly, the D-form (having right-handed nanofibers) of both hydrogels (MTZ and TDZ) exhibited higher antibacterial activities compared with the left-handed nanofibrous hydrogels (L-form) attributed to the stereoselective interaction of the chiral helical nanofiber. Moreover, the amplification of chirality moving from a molecular to a supramolecular level essentially improved the antibacterial action. Our results provide deep insight into the development of unique supramolecular chiral antimicrobial agents and hint at the potentiality of right-handed nanofibers (D-form) having enhanced antibacterial activity. STATEMENT OF SIGNIFICANCE: Chiral stereochemistry plays a significant role in many biological processes, which determines the interaction of bacteria cells with chiral biomolecules. The interaction between bacteria and material surface (molecular chirality or supramolecular chirality) plays a significant role in modulating antibacterial performance. Here, we deigned and synthesized unique inherent biocompatible supramolecular chiral hydrogel. From this study we concluded that the D-form (having right-handed nanofibers) of hydrogels exhibited higher antibacterial activities compared with the left-handed nanofibrous hydrogels (L-form) attributed to the stereoselective interaction of the chiral helical nanofiber. Additionally, this study also explored the amplification of chirality moving from a molecular to a supramolecular level essentially improved the antibacterial action.

Fast Gelation of Poly(ionic liquid)-Based Injectable Antibacterial Hydrogels

Traditional antibacterial hydrogels have a broad-spectrum bactericidal effect and are widely used as wound dressings. However, the biological toxicity and drug resistance of these antibacterial hydrogels cannot meet the requirements of long-term clinical application. Imidazolium poly(ionic liquids) (PILs) are polymeric antibacterial agents exhibiting strong antibacterial properties, as they contain a strong positive charge. In this study, two imidazolium PILs, namely poly(N-butylimidazolium propiolic acid sodium) (PBP) and poly(N-(3,6-dioxaoctane) imidazolium propiolic acid sodium) (PDP), as high efficiency antibacterial agents, were synthesized by polycondensation reaction. Then, the PILs were compounded with polyethylene glycol (PEG) by a thiol-yne click reaction to prepare injectable antibacterial hydrogels. An in vitro assay showed that the injectable antibacterial hydrogels could not only quickly kill Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), but also had low toxicity for human skin fibroblasts cells (HSFs) and human umbilical vein endothelial cells (HUVECs), respectively. Additionally, the lipopolysaccharide (LPS) inflammation model revealed that the injectable antibacterial hydrogels also had anti-inflammatory effects, which would be advantageous to accelerate wound healing.

Supramolecular Polymeric Prodrug Micelles for Efficient Anticancer Drug Delivery

Polymeric prodrugs have attracted great interest in the field of antitumor drug delivery owing to its integrated advantages of prodrugs and nanoparticles. However, the ambiguous chemical composition of polymeric prodrugs...

Synthesis, classification and properties of hydrogels: their applications in drug delivery and agriculture

Absorbent polymers or hydrogel polymer materials have an enhanced water retention capacity and are widely used in agriculture and medicine. The controlled release of bioactive molecules (especially drug proteins) by hydrogels and the encapsulation of living cells are some of the active areas of drug discovery research. Hydrogel-based delivery systems may result in a therapeutically advantageous outcome for drug delivery. They can provide various sequential therapeutic agents including macromolecular drugs, small molecule drugs, and cells to control the release of molecules. Due to their controllable degradability, ability to protect unstable drugs from degradation and flexible physical properties, hydrogels can be used as a platform in which various chemical and physical interactions with encapsulated drugs for controlled release in the system can be studied. Practically, hydrogels that possess biodegradable properties have aroused greater interest in drug delivery systems. The original three-dimensional structure gets broken down into non-toxic substances, thus confirming the excellent biocompatibility of the gel. Chemical crosslinking is a resource-rich method for forming hydrogels with excellent mechanical strength. But in some cases the crosslinker used in the synthesis of the hydrogels may cause some toxicity. However, the physically cross-linked hydrogel preparative method is an alternative solution to overcome the toxicity of cross-linkers. Hydrogels that are responsive to stimuli formed from various natural and synthetic polymers can show significant changes in their properties under external stimuli such as temperature, pH, light, ion changes, and redox potential. Stimulus-responsive hydrogels have a wider range of applications in biomedicine including drug delivery, gene delivery and tissue regeneration. Stimulus-responsive hydrogels loaded with multiple drugs show controlled and sustained drug release and can act as drug carriers. By integrating stimulus-responsive hydrogels, such as those with improved thermal responsiveness, pH responsiveness and dual responsiveness, into textile materials, advanced functions can be imparted to the textile materials, thereby improving the moisture and water retention performance, environmental responsiveness, aesthetic appeal, display and comfort of textiles. This review explores the stimuli-responsive hydrogels in drug delivery systems and examines super adsorbent hydrogels and their application in the field of agriculture.

Chiral Orchestration: A Tool for Fishing Out Tripeptide-Based Mechanoresponsive Supergelators Possessing Anti-Inflammatory and Antimicrobial Properties

Deciphering the most promising strategy for the evolution of microbial infection and inflammation-based therapeutics is one of the most challenging affairs to date. Development of peptide-based smart supergelators with innate antimicrobial and anti-inflammatory activities is an appealing way out. In this work, the hydrogelators Boc-δ-Ava-(X)-Phe-(Y)-Phe-OH (I: X = Y = L; II: X = L; Y = D; III: X = D; Y = L; IV: X = Y = D, Ava: δ-amino valeric acid) have been designed and fabricated by strategic chiral tuning to investigate the effect of alternation of configuration(s) of Phe residues in governing the fashion of self-aggregation and macroscopic properties of peptides. Interestingly, all of the molecules formed mechanoresponsive hydrogels under physiological conditions with a nanofibrillar network. The spectroscopic experiments confirmed the conformation of the hydrogelators to be supramolecular β-sheets formed through the self-association of S-shaped constructs stabilized by noncovalent interactions. Indeed, the present work demonstrates a rational approach toward regulating the mechanical integrity of the hydrogels through systematic inclusion of d-amino acids at appropriate positions in the sequence. The hydrogelators were found to possess antimicrobial activity against both Gram-positive bacteria (Staphylococcus aureus and Streptococcus mutans) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumonia) while retaining their biocompatibility toward mammalian cells (as revealed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), hemolysis, and lipid peroxidation assays). These scaffolds also exhibited anti-inflammatory activities, as observed through in vitro MMP2/MMP9 inhibition studies and in vivo animal models, namely, the rat pouch model for acute inflammation. We anticipate that the discovery of these intelligent materials with multifunctional capabilities holds future promise as preferential therapeutics for the treatment of bacterial infections as well as associated inflammations arising alone or as side effects of biomaterial implants.

Fabrication of a Dual-Action Membrane with Both Antibacterial and Anticoagulant Properties via Cationic Polyelectrolyte-Induced Phase Separation

The development of microorganisms and formation of thrombus on a biomaterial surface can seriously lead to device failure and threaten human health. Nonetheless, a surface that has both antibacterial and anticoagulant properties has scarcely been developed. Herein, a novel dual-action membrane composed of polyethersulfone (PES) bulk material and a hydrophilic anionic poly-2-acrylamido-2-methylpropanesulfonic acid (PAMPS) polymer has been prepared via the cationic antibacterial agent poly(hexamethylene biguanide) (PHMB)-induced phase separation technique. Interestingly, the resultant membrane can offer tunable antibacterial and anticoagulant properties, while maintaining satisfactory permeability and greatly increasing selectivity. The membrane also shows excellent hydrophilicity, a well-defined porous surface, and cross section with a sponge gradient structure. Furthermore, the PHMB-PAMPS complex formed on the membrane surface displays outstanding long-term stability, which is crucial for further practical applications. More importantly, the hollow fiber membrane fabricated by the cationic polyelectrolyte-induced phase separation technique confirms its capability to control the membrane permeability (257.4 L·m^-2·h^-1·bar^-1) and selectivity (95.9%) without destroying the membrane structure. The present work opens a straightforward and efficient avenue for the rational design of a functional surface to fight biomedical material-associated infections.

Synthesis of antibacterial polyether biguanide curing agent and its cured antibacterial epoxy resin

At present, bacteria continue to threaten human health, and the resistance of bacteria to antibiotics continues to increase, so the development of new antibacterial agents and antibacterial materials is increasingly important to ensure human health. In this paper, three polyether biguanide compounds with high antibacterial properties were synthesized by reacting polyetheramine T403 with o-tolylbiguanide, m-tolylbiguanide and p-tolylbiguanide (o-TTB, m-TTB and p-TTB), respectively. The antimicrobial performance of polyether biguanide against E. coli and S. aureus was evaluated using a minimum inhibitory concentration method, and the results showed that the synthesized polyether biguanide exhibited efficient and broad-spectrum antimicrobial effects. Among them, o-tolyl biguanide derivative o-TTB showed the best antimicrobial performance, with minimum inhibitory concentrations of 20 and 15 μg/mL against E. coli and S. aureus, respectively. Then, epoxy resin E51 was cured using the obtained TTB as a curing agent to prepare an epoxy resin with antibacterial properties. The inhibition of the growth of S. aureus by the cured o-TTB/E51 resin was investigated by incubating the cured epoxy resin with bacteria, and the results showed that the cured resin had a significant inhibitory effect on the growth of bacteria. The non-isothermal curing kinetics of the o-TTB/E51 system were investigated by differential scanning calorimetry (DSC) to determine the optimized curing reaction temperature, curing kinetic parameters and curing kinetics equation.

A simple hydrogel scaffold with injectability, adhesivity and osteogenic activity for bone regeneration

A simple hydrogel scaffold with injectability, adhesivity and osteogenic activity is facilely prepared by directly mixing strontium chloride and Alg-DA aqueous solutions.

Advances in dual functional antimicrobial and osteoinductive biomaterials for orthopaedic applications

A vast growing problem in orthopaedic medicine is the increase of clinical cases with antibiotic resistant pathogenic microbes, which is predicted to cause higher mortality than all cancers combined by 2050. Bone infectious diseases limit the healing ability of tissues and increase the risk of future injuries due to pathologic tissue remodelling. The traditional treatment for bone infections has several drawbacks and limitations, such as lengthy antibiotic treatment, extensive surgical interventions, and removal of orthopaedic implants and/or prosthesis, all of these resulting in long-term rehabilitation. This is a huge burden to the public health system resulting in increased healthcare costs. Current technologies e.g. co-delivery systems, where antibacterial and osteoinductive agents are delivered encounter challenges such as site-specific delivery, sustained and prolonged release, and biocompatibility. In this review, these aspects are highlighted to promote the invention of the next generation biomaterials to prevent and/or treat bone infections and promote tissue regeneration.

Facile and Versatile Modification of Cotton Fibers for Persistent Antibacterial Activity and Enhanced Hygroscopicity

Natural fibers with functionalities have attracted considerable attention. However, developing facile and versatile strategies to modify natural fibers is still a challenge. In this study, cotton fibers, the most widely used natural fibers, were partially oxidized by sodium periodate in aqueous solution, to give oxidized cotton fibers containing multiple aldehyde groups on their surface. Then poly(hexamethylene guanidine) was chemically grafted onto the oxidized cotton fibers forming Schiff bases between the terminal amines of poly(hexamethylene guanidine) and the aldehyde groups of oxidized cotton fibers. Finally, carbon-nitrogen double bonds were reduced by sodium cyanoborohydride, to bound poly(hexamethylene guanidine) covalently to the surface of cotton fibers. These functionalized fibers show strong and persistent antibacterial activity: complete inhibition against Escherichia coli and Staphylococcus aureus was maintained even after 1000 consecutive washing in distilled water. On the other hand, cotton fibers with only physically adsorbed poly(hexamethylene guanidine) lost their antibacterial activity entirely after a few washes. According to Cell Counting Kit-8 assay and hemolytic analysis, toxicity did not significantly increase after chemical modification. Attributing to the hydrophilicity of poly(hexamethylene guanidine) coatings, the modified cotton fibers were also more hygroscopic compared to untreated cotton fibers, which can improve the comfort of the fabrics made of modified cotton fibers. This study provides a facile and versatile strategy to prepare modified polysaccharide natural fibers with durable antibacterial activity, biosecurity, and comfortable touch.

Investigations of Peptide-Based Biocompatible Injectable Shape-Memory Hydrogels: Differential Biological Effects on Bacterial and Human Blood Cells

Here, we report the self-assembly of Amoc (9-anthracenemethoxycarbonyl)-capped dipeptides, which self-assemble to form injectable, self-healable, and shape-memory hydrogels with inherent antibacterial properties. Amoc-capped dipeptides self-assemble to form nanofibrillar networks, which are established by several spectroscopic and microscopic techniques. The inherent antibacterial properties of hydrogels are evaluated using two Gram-positive Staphylococcus aureus, Bacillus subtilis and three Gram-negative Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi bacteria. These hydrogels exhibit potent antibacterial efficacy against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentrations (MIC₅₀) for the hydrogels on Gram-positive bacteria are in the range of 10-200 μM hydrogelator concentrations. The biocompatibility and cytotoxicity of the hydrogels are evaluated using 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), hemolysis, and lipid peroxidation (LPO) assay on human blood cells. The hydrogels are hemocompatible and they decrease LPO values on human red blood cells probably via increased cellular stability against oxidative stress. Furthermore, MTT data show that the hydrogels are biocompatible and promote cell viability and proliferation on cultured human white blood cells. Taken together, these results may suggest that our designed injectable hydrogels could be useful to prevent localized bacterial infections.

Injectable and Degradable pH-Responsive Hydrogels via Spontaneous Amino-Yne Click Reaction

Injectable hydrogels have attracted increasing attention in tissue regeneration and local drug delivery applications. Current click reactions for preparing injectable hydrogels often require a photoinitiator or catalyst, which may be toxic and may involve complex synthesis of precursors. Here, we report a facile and inexpensive method to prepare injectable and degradable hydrogels via spontaneous amino-yne click reaction without using any initiator or catalyst under physiological conditions based on telechelic electron-deficient dipropiolate ester of polyethylene glycol and water-soluble commercially available carboxymethyl chitosan (CMC). The gelation time, mechanical property, and degradation rate of the hydrogels could be adjusted by varying CMC concentrations and stoichiometric ratios. The reversible pH-induced sol-gel transitions of the hydrogel are presented and the pH-controlled drug release behaviors are demonstrated, of which the mechanism is discussed. In vitro cytotoxicity assays and in vivo in situ injection study of the CMC-based hydrogels showed favorable gel formation, nontoxicity, and good tissue biocompatibility. Therefore, these biodegradable and injectable hydrogels prepared by spontaneous amino-yne click reaction hold potential for tissue engineering and other biomedical applications.

Hydrophilic and antimicrobial core–shell nanoparticles containing guanidine groups for ultrafiltration membrane modification

Physical blending is a common technique to improve the water flux and antifouling performance of ultrafiltration (UF) membranes. In the present work, a novel hydrophilic and antimicrobial core–shell nanoparticle was synthesized through the chemical grafting of poly(guanidine-hexamethylenediamine-PEI) (poly(GHPEI)) on the surface of silica nanoparticles (SNP). The synthesized core–shell nanoparticles, poly(GHPEI) functionalized silica nanoparticles (SNP@PG), were incorporated into polyethersulfone (PES) to fabricate hybrid UF membranes by a phase inversion process. The chemical composition, surface and cross section morphologies, hydrophilicity, water flux and protein rejection of the membranes were evaluated by a series of characterizations. Results show that the prepared PES/SNP@PG hybrid membrane exhibits not only improved water flux, which is around 2.6 times that of the pristine PES membrane, but also excellent resistance to organic fouling and biofouling.

Hydrophilic and antimicrobial core–shell nanoparticles containing guanidine groups (SNP@PG) were applied to fabricate membranes with improved water flux and fouling resistance.

Cross-Linking of a Hydrophilic, Antimicrobial Polycation toward a Fast-Swelling, Antimicrobial Superabsorber and Interpenetrating Hydrogel Networks with Long Lasting Antimicrobial Properties

A hemocompatible, antimicrobial 3,4en-ionene (PBI) derived by polyaddition of trans-1,4-dibromo-2-butene and N,N,N',N'-tetramethyl-1,3-propanediamine was cross-linked via its bromine end groups using tris(2-aminoethyl)amine (TREN) to form a fast-swelling, antimicrobial superabsorber. This superabsorber is taking up the 30-fold of its weight in 60 s and the granulated material is taking up 96-fold of its weight forming a hydrogel. It fully prevents growth of the bacterium Staphylococcus aureus. The PBI network was swollen with 2-hydroxyethyl acrylate and glycerol dimethacrylate followed by photopolymerization to form an interpenetrating hydrogel (IPH) with varying PBI content in the range of 2.0 to 7.8 wt %. The nanophasic structure of the IPH was confirmed by atomic force microscopy and transmission electron microscopy. The bacterial cells of the nosocomial strains Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa are killed on the IPH even at the lowest PBI concentration. The antimicrobial activity was retained after washing the hydrogels for up to 4 weeks. The IPHs show minor leaching of PBI far below its antimicrobial active concentration using a new quantitative test for PBI detection in solution. This leaching was shown to be insufficient to form an inhibition zone and killing bacterial cells in the surroundings of the IPH.

Injectable Pore-Forming Hydrogel Scaffolds for Complex Wound Tissue Engineering: Designing and Controlling Their Porosity and Mechanical Properties

Traumatic soft tissue wounds present a significant reconstructive challenge. The adoption of closed-circuit negative pressure wound therapy (NPWT) has enabled surgeons to temporize these wounds before reconstruction. Such systems use porous synthetic foam scaffolds as wound fillers at the interface between the negative pressure system and the wound bed. The idea of using a bespoke porous biomaterial that enhances wound healing, as filler for an NPWT system, is attractive as it circumvents concerns regarding reconstructive delay and the need for dressing changes that are features of the current systems. Porous foam biomaterials are mechanically robust and able to synthesize in situ. Hence, they exhibit potential to fulfill the niche for such a functionalized injectable material. Injectable scaffolds are currently in use for minimally invasive surgery, but the design parameters for large-volume expansive foams remain unclear. Potential platforms include hydrogel systems, (particularly superabsorbent, superporous, and nanocomposite systems), polyurethane-based moisture-cured foams, and high internal phase emulsion polymer systems. The aim of this review is to discuss the design parameters for such future biomaterials and review potential candidate materials for further research into this up and coming field.

Injectable camptothecin conjugated hydrogels with simultaneous drug release and degradation

Novel injectable camptothecin conjugated hydrogels with simultaneous drug release and degradation properties were prepared, which show significant cytotoxicity to HepG2 cells, and could be a potential candidate for intratumor drug delivery.