Functional Hydrogels and Their Application in Drug Delivery, Biosensors, and Tissue Engineering

Artificial Intelligence tool for prediction of ECM mimics hydrogel formulations via click chemistry

A user-friendly machine learning (ML) predictive tool is reported for designing extracellular matrix (ECM)-mimetic hydrogels with tailored rheological properties. Developed for regenerative medicine and 3D bioprinting, the model leverages click chemistry crosslinking to fine-tune the mechanical behaviour of gelatin- and hyaluronic acid-based hydrogels. Using both experimental rheological data and synthetic datasets, our supervised ML approach accurately predicts hydrogel compositions, significantly reducing the cost and time associated with trial-and-error approach. Despite advancements in the field, existing models remain limited in their ability to mimic the ECM due to the use of non-natural polymers, reliance on a single type of biologically active macromolecule, and physical crosslinking reactions with limited tuneability. Additionally, their lack of generalizability confines them to specific formulations and demands extensive experimental data for training. This predictive platform represents a major advancement in biomaterial design, improving reproducibility, scalability, and efficiency. By integrating rational design, it accelerates tissue engineering research and expands access to customized ECM-mimetic hydrogels with tailored viscoelastic properties for biomedical applications, enabling both experts and non-experts in materials design.

Self-healing, 3D printed bioinks from self-assembled peptide and alginate hybrid hydrogels

There is a pressing need for new cell-laden, printable, biomaterials that are rigid and highly biocompatible. These materials can mimic stiffer tissues such as cartilage, fibrotic tissue and cancer microenvironments, and thus have exciting applications in regenerative medicine, wound healing and cancer research. Self-assembled peptides (SAPs) functionalised with aromatic groups such as Fluorenyl-9-methoxycarbonyl (Fmoc) show promise as components of these biomaterials. However, the harsh basic conditions often used to solubilise SAPs leads to issues with toxicity and reproducibility. Here, we have designed a hybrid material comprised of self-assembled Fmoc-diphenylalanine (Fmoc-FF) assemblies dispersed throughout a sodium alginate matrix and investigated the influence of different organic solvents as peptide solubilising agents. Bioinks fabricated from peptides dissolved in 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) showed improved biocompatibility compared to those made from Dimethyl Sulfoxide (DMSO) peptide stocks, due to the increased volatility and reduced surface tension of HFIP, allowing for more efficient expulsion from the system. Through optimisation of assembly and solvent conditions we can generate hybrid bioinks with stiffnesses up to 8 times greater than sodium alginate alone that remain highly printable, even when laden with high concentrations of cells. In addition, the shear-thinning nature of the self-assembled peptide assemblies gave the hybrid bioinks highly desirable self-healing capabilities. Our developed hybrid materials allow the bioprinting of materials previously considered too stiff to extrude without causing shear induced cytotoxicity with applications in tissue engineering and biosensing.

The Application of Resolvin D1-Loaded Gelatin Methacrylate in a Rat Periodontitis Model

Objective: To evaluate the drug release, cytocompatibility with periodontal ligament cells (PDLCs), and therapeutic efficacy of GelMA hydrogel loaded with resolvin D1 (RvD1) in treating rat periodontal inflammation and alveolar bone damage. Methods: An RvD1 complexed with GelMA was prepared, and its release kinetics and compatibility with PDLCs were assessed. Rats with induced periodontitis were treated weekly with topical applications of vehicle, GelMA, RvD1, or RvD1 complexed with GelMA for four weeks. Periodontal inflammation and tissue regeneration were evaluated using quantitative PCR (qPCR) and histochemical staining, while alveolar bone repair and regeneration were analyzed through micro-CT. Results: The RvD1 complexed with GelMA effectively released RvD1 and enhanced the proliferation and viability of PDLCs. Compared to RvD1 alone, treatment with RvD1 complexed with GelMA significantly reduced inflammatory cell infiltration, TNF-α and RANKL expression, and osteoclast formation in periodontal tissues. Additionally, it promoted the expression of specific anti-inflammatory and regenerative markers. Micro-CT analysis confirmed significant new bone formation in the RvD1 complexed with GelMA-treated group. Conclusions: RvD1 complexed with GelMA provides sustained drug release and biocompatibility, effectively resolves periodontal inflammation, and promotes tissue regeneration in periodontitis.

Nanoengineering-armed oncolytic viruses drive antitumor response: progress and challenges

Oncolytic viruses (OVs) have emerged as a powerful tool in cancer therapy. Characterized with the unique abilities to selectively target and lyse tumor cells, OVs can expedite the induction of cell death, thereby facilitating effective tumor eradication. Nanoengineering-derived OVs overcome traditional OV therapy limitations by enhancing the stability of viral circulation, and tumor targeting, promising improved clinical safety and efficacy and so on. This review provides a comprehensive analysis of the multifaceted mechanisms through which engineered OVs can suppress tumor progression. It initiates with a concise delineation on the fundamental attributes of existing OVs, followed by the exploration of their mechanisms of the antitumor response. Amid rapid advancements in nanomedicine, this review presents an extensive overview of the latest developments in the synergy between nanomaterials, nanotechnologies, and OVs, highlighting the unique characteristics and properties of the nanomaterials employed and their potential to spur innovation in novel virus design. Additionally, it delves into the current challenges in this emerging field and proposes strategies to overcome these obstacles, aiming to spur innovation in the design and application of next-generation OVs.

Vitamin K (Menadione)-incorporated chitosan/alginate hydrogel as a novel product for periorbital hyperpigmentation

The possibility of controlling periorbital hyperpigmentation disorders is one of the most important research goals in cosmetic preparations. In the current investigation, 1% vitamin K (Vit K) was incorporated into a Chitosan/alginate hydrogel which aimed to increase the dermal delivery and anti-pigmentation effect. The Vit K-hydrogel was evaluated using several different tests, including volume expansion/contraction analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), ultraviolet (UV) absorbance spectroscopy, and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Vit K hydrogel's drug release profile showed a steady increase over time. Furthermore, the modified Vit K hydrogel formulations showed no harmful effects in an in vitro cytotoxicity study. The Vit K hydrogel was tested for dermal irritation on Wistar rats, and the hydrogel was found to be non-irritating. Furthermore, Vit K-hydrogel inhibited melanin formation (31.76 ± 1.14%) and was remarkably higher than free Vit K. In addition, Vit K-hydrogel inhibited L-dopa auto-oxidation to a greater extent (94.80 ± 2.41%) in comparison with Vit K solution (73.95 ± 1.62%). Vit K-hydrogel enhanced percutaneous transport of Vit K, according to in vitro percutaneous absorption findings, suggesting that this innovative formulation may provide new therapeutic options for periorbital hyperpigmentation.

The Recent Progress of the Cellulose-Based Antibacterial Hydrogel

Cellulose-based antibacterial hydrogel has good biocompatibility, antibacterial performance, biodegradability, and other characteristics. It can be very compatible with human tissues and degradation, while its good water absorption and moisturizing properties can effectively absorb wound exudates, keep the wound moist, and promote wound healing. In this paper, the structural properties, and physical and chemical cross-linking preparation methods of cellulose-based antibacterial hydrogels were discussed in detail, and the application of cellulose-based hydrogels in the antibacterial field was deeply studied. In general, cellulose-based antibacterial hydrogels, as a new type of biomaterial, have shown good potential in antimicrobial properties and have been widely used. However, there are still some challenges, such as optimizing the preparation process and performance parameters, improving the antibacterial and physical properties, broadening the application range, and evaluating safety. However, with the deepening of research and technological progress, it is believed that cellulose-based antibacterial hydrogels will be applied and developed in more fields in the future.

Self-Healable Adhesive Hydrogel with a Preserved Underwater Adhesive Ability Based on Histidine-Zinc Coordination and a Bioengineered Hybrid Mussel Protein

Mussels are marine organisms that are capable of constructing an underwater adhesion between their bodies and rigid structures. It is well known that mussels achieve underwater adhesion through the presence of mussel adhesive proteins (MAPs) that contain high levels of 3,4-dihydroxyphenylalanine (DOPA). Although the extraordinary underwater adhesive properties of mussels are attributed to DOPA, its capacity to play a dual role in surface adhesion and internal cohesion is inherently limited. However, mussels employ a combination of chemical moieties, not just DOPA, along with anatomical components, such as plaque and byssus, in underwater adhesion. This also involves junction proteins that connect the plaque and byssus. In this study, a novel hybrid MAP was bioengineered via the fusion of the plaque protein (foot protein type 1) and the histidine-rich domain of the junction protein (foot protein type 4). To achieve direct adhesion underwater, the adhesive should maintain surface adhesion without disintegrating. Notably, the histidine-Zn-coordinated hybrid MAP hydrogel maintained a high surface adhesion ability even after cross-linking because of the preservation of its unoxidized and non-cross-linked DOPA moieties. The formulated adhesive hydrogel system based on the bioengineered hybrid MAP exhibited self-healing properties, owing to the reversible metal coordination bonds. The developed adhesive hydrogel exhibits outstanding levels of bulk adhesion in underwater environments, highlighting its potential as an effective adhesive biomaterial. Therefore, the introduction of histidine-rich domains into MAPs may be applied in various studies to formulate mussel-inspired adhesives with self-healing properties and to fully utilize the adhesive ability of DOPA.

Aggregation-Induced Emission Luminogen-Encapsulated Fluorescent Hydrogels Enable Rapid and Sensitive Quantitative Detection of Mercury Ions

Hg²⁺ contamination in sewage can accumulate in the human body through the food chains and cause health problems. Herein, a novel aggregation-induced emission luminogen (AIEgen)-encapsulated hydrogel probe for ultrasensitive detection of Hg²⁺ was developed by integrating hydrophobic AIEgens into hydrophilic hydrogels. The working mechanism of the multi-fluorophore AIEgens (TPE-RB) is based on the dark through-bond energy transfer strategy, by which the energy of the dark tetraphenylethene (TPE) derivative is completely transferred to the rhodamine-B derivative (RB), thus resulting in intense photoluminescent intensity. The spatial networks of the supporting hydrogels further provide fixing sites for the hydrophobic AIEgens to enlarge accessible reaction surface for hydrosoluble Hg²⁺, as well create a confined reaction space to facilitate the interaction between the AIEgens and the Hg²⁺. In addition, the abundant hydrogen bonds of hydrogels further promote the Hg²⁺ adsorption, which significantly improves the sensitivity. The integrated TPE-RB-encapsulated hydrogels (TR hydrogels) present excellent specificity, accuracy and precision in Hg²⁺ detection in real-world water samples, with a 4-fold higher sensitivity compared to that of pure AIEgen probes. The as-developed TR hydrogel-based chemosensor holds promising potential as a robust, fast and effective bifunctional platform for the sensitive detection of Hg²⁺.

Phage engineering and phage-assisted CRISPR-Cas delivery to combat multidrug-resistant pathogens

Antibiotic resistance ranks among the top threats to humanity. Due to the frequent use of antibiotics, society is facing a high prevalence of multidrug resistant pathogens, which have managed to evolve mechanisms that help them evade the last line of therapeutics. An alternative to antibiotics could involve the use of bacteriophages (phages), which are the natural predators of bacterial cells. In earlier times, phages were implemented as therapeutic agents for a century but were mainly replaced with antibiotics, and considering the menace of antimicrobial resistance, it might again become of interest due to the increasing threat of antibiotic resistance among pathogens. The current understanding of phage biology and clustered regularly interspaced short palindromic repeats (CRISPR) assisted phage genome engineering techniques have facilitated to generate phage variants with unique therapeutic values. In this review, we briefly explain strategies to engineer bacteriophages. Next, we highlight the literature supporting CRISPR-Cas9-assisted phage engineering for effective and more specific targeting of bacterial pathogens. Lastly, we discuss techniques that either help to increase the fitness, specificity, or lytic ability of bacteriophages to control an infection.

Development of mussel mimetic gelatin based adhesive hydrogel for wet surfaces with self-healing and reversible properties

Gelatin, being a naturally derived biomacromolecule shows good biocompatibility and biodegradability and hence turn out to be a potential biomaterial in synthesizing adhesive hydrogel. However, to achieve significant adhesive strength under wet condition and good mechanical properties, gelatin is functionalised with dopamine and acrylic acid. Here, inspired from nature, we have developed a gelatin based adhesive hydrogel for wet surfaces by incorporating dopamine into gelatin-poly(acrylic acid) chain. The synthesized hydrogel demonstrate good mechanical strength, high stretchability, reversibility, self-healing and dynamic adhesive behaviour along with long term reusability. The adhesive strength of the synthesized hydrogel to tissue surface was found to be 6.5 KPa when applied under submerged condition. Moreover, the swelling behaviour of the hydrogel reveals that hydrogel have limited swellability thereby retaining adhesive property under fully swollen state. Haemolysis results reveals the biocompatible nature of the hydrogel. Thus this hydrogel emerge to be a promising bioadhesive for application in various fields mostly in biomedical devices.

Nanostructured multifunctional stimuli-responsive glycopolypeptide-based copolymers for biomedical applications

Inspired by natural resources, such as peptides and carbohydrates, glycopolypeptide biopolymer has recently emerged as a new form of biopolymer being recruited in various biomedical applications. Glycopolypeptides with well-defined secondary structures and pendant glycosides on the polypeptide backbone have sparked lots of research interest and they have an innate ability to self-assemble in diverse structures. The nanostructures of glycopolypeptides have also opened up new perspectives in biomedical applications due to their stable three-dimensional structures, high drug loading efficiency, excellent biocompatibility, and biodegradability. Although the development of glycopolypeptide-based nanocarriers is well-studied, their clinical translation is still limited. The present review highlights the preparation and characterization strategies related to glycopolypeptides-based copolymers, followed by a comprehensive discussion on their biomedical applications with a specific focus on drug delivery by various stimuli-responsive (e.g., pH, redox, conduction, and sugar) nanostructures, as well as their beneficial usage in diagnosis and regenerative medicine.

Drug Delivery Systems as a Strategy to Improve the Efficacy of FDA-Approved Alzheimer's Drugs

Alzheimer's disease (AD) is the most common form of dementia, with a high impact worldwide, accounting for more than 46 million cases. The continuous increase of AD demands the fast development of preventive and curative therapeutic strategies that are truly effective. The drugs approved for AD treatment are classified into acetylcholinesterase inhibitors and N-methyl-D-aspartate receptor antagonists. The therapeutic effectiveness of those drugs is hindered by their restricted access to the brain due to the blood-brain barrier, low bioavailability, and poor pharmacokinetic properties. In addition, the drugs are reported to have undesirable side effects. Several drug delivery systems (DDSs) have been widely exploited to address these issues. DDSs serve as drug carriers, combining the ability to deliver drugs locally and in a targeted manner with the ability to release them in a controlled and sustained manner. As a result, the pharmacological therapeutic effectiveness is raised, while the unwanted side effects induced by the unspecific distribution decrease. This article reviews the recently developed DDSs to increase the efficacy of Food and Drug Administration-approved AD drugs.

Multifunctional Composite Hydrogels for Bacterial Capture, Growth/Elimination, and Sensing Applications

Hydrogels are cross-linked networks of hydrophilic polymer chains with a three-dimensional structure. Owing to their unique features, the application of hydrogels for bacterial/antibacterial studies and bacterial infection management has grown in importance in recent years. This trend is likely to continue due to the rise in bacterial infections and antimicrobial resistance. By exploiting their physicochemical characteristics and inherent nature, hydrogels have been developed to achieve bacterial capture and detection, bacterial growth or elimination, antibiotic delivery, or bacterial sensing. Traditionally, the development of hydrogels for bacterial/antibacterial studies has focused on achieving a single function such as antibiotic delivery, antibacterial activity, bacterial growth, or bacterial detection. However, recent studies demonstrate the fabrication of multifunctional hydrogels, where a single hydrogel is capable of performing more than one bacterial/antibacterial function, or composite hydrogels consisting of a number of single functionalized hydrogels, which exhibit bacterial/antibacterial function synergistically. In this review, we first highlight the hydrogel features critical for bacterial studies and infection management. Then, we specifically address unique hydrogel properties, their surface/network functionalization, and their mode of action for bacterial capture, adhesion/growth, antibacterial activity, and bacterial sensing, respectively. Finally, we provide insights into different strategies for developing multifunctional hydrogels and how such systems can help tackle, manage, and understand bacterial infections and antimicrobial resistance. We also note that the strategies highlighted in this review can be adapted to other cell types and are therefore likely to find applications beyond the field of microbiology.

Three-dimensional tailor-made collagen-like proteins hydrogel for tissue engineering applications

Despite the potential tunable properties of blank slate collagen-like proteins (CLP), an alternative to animal-originated collagen, assembling them into a stable 3D hydrogel to mimic extracellular matrix is a challenge. To address this constraint, the CLP (without hydroxyproline, CLPpro) and its variants encoding functional unnatural amino acids such as hydroxyproline (CLPhyp) and 3,4-dihydroxyphenylalanine (CLPdopa) were generated through genetic code engineering for 3D hydrogel development. The CLPhyp and CLPdopa were chosen to enhance the intermolecular hydrogen bond interaction through additional hydroxyl moiety and thereby facilitate the self-assembly into a fibrillar network of the hydrogel. Hydrogelation was induced through genipin as a cross-linker, enabling intermolecular cross-linking to form a hydrogel. Spectroscopic and rheological analyses confirmed that CLPpro and its variants maintained native triple-helical structure, which is necessary for its function, and viscoelastic nature of the hydrogels, respectively. Unlike CLPpro, the varients (CLPhyp and CLPdopa) increased pore size formation in the hydrogel scaffold, facilitating 3T3 fibroblast cell interactions. DSC analysis indicated that the stability of the hydrogels got increased upon the genetic incorporation of hydroxyproline (CLPhyp) and dopa (CLPdopa) in CLPpro. In addition, CLPdopa hydrogel was found to be relatively stable against collagenase enzyme compared to CLPpro and CLPhyp. It is the first report on 3D biocompatible hydrogel preparation by tailoring CLP sequence with non-natural amino acids. These next-generation tunable CLP hydrogels open a new venue to design synthetic protein-based biocompatible 3D biomaterials for tissue engineering applications.

Functional Thermoresponsive Hydrogel Molecule to Material Design for Biomedical Applications

Temperature-induced, rapid changes in the viscosity and reproducible 3-D structure formation makes thermos-sensitive hydrogels an ideal delivery system to act as a cell scaffold or a drug reservoir. Moreover, the hydrogels’ minimum invasiveness, high biocompatibility, and facile elimination from the body have gathered a lot of attention from researchers. This review article attempts to present a complete picture of the exhaustive arena, including the synthesis, mechanism, and biomedical applications of thermosensitive hydrogels. A special section on intellectual property and marketed products tries to shed some light on the commercial potential of thermosensitive hydrogels.

Injectable DNA Hydrogel-Based Local Drug Delivery and Immunotherapy

Regulated drug delivery is an important direction in the field of medicine and healthcare research. In recent years, injectable hydrogels with good biocompatibility and biodegradability have attracted extensive attention due to their promising application in controlled drug release. Among them, DNA hydrogel has shown great potentials in local drug delivery and immunotherapy. DNA hydrogel is a three-dimensional network formed by cross-linking of hydrophilic DNA strands with extremely good biocompatibility. Benefiting from the special properties of DNA, including editable sequence and specificity of hybridization reactions, the mechanical properties and functions of DNA hydrogels can be precisely designed according to specific applications. In addition, other functional materials, including peptides, proteins and synthetic organic polymers can be easily integrated with DNA hydrogels, thereby enriching the functions of the hydrogels. In this review, we first summarize the types and synthesis methods of DNA hydrogels, and then review the recent research progress of injectable DNA hydrogels in local drug delivery, especially in immunotherapy. Finally, we discuss the challenges facing DNA hydrogels and future development directions.

Radiation synthesis and anticancer drug delivery of poly(acrylic acid/acrylamide) magnetite hydrogel

Hydrogels had gained considerable importance in drug delivery systems. Polyacrylic acid/acrylamide (AAc/AAm) and polyacrylic acid/acrylamide doped with magnetite (AAc/AAm)Fe3O4 hydrogels have been prepared by ɣ-radiations and characterized by Fourier transform infrared spectra (IR), X-ray diffractions (XRD), scanning electron microscope (SEM) and transmittance electron microscope (TEM). The morphology and the particle size were determined from TEM images. The average particle size of Fe3O4 was found to be 12 nm. The degree of cross-linking of Poly (AAc/AAm) hydrogel was determined from the gel fraction at different radiation doses and compositions. Swelling of the hydrogel was studied at different conditions. The magnetism of (AAc/AAm) Fe3O4 was studied by vibrating sample magnetometer and the results indicated super-paramagnetic character of (AAc/AAm)Fe3O4. The band gap (Eg) was determined and the values suggested semi-conductivity of the hydrogels. Doxorubicin loading and release by (AAc/AAm)Fe3O4 hydrogel was studied and indicated that the hydrogel can load 78% of doxorubicin.

NANOCOMPOSITES BASED ON SINGLECOMPONENT AND MULTICOMPONENT POLYMER MATRICES FOR BIOMEDICAL APPLICATIONS

The review is devoted to analysis of the publications in the area of polymers of biomedical applications. Different types of the polymer matrices for drug delivery are analyzed, including polyurethanes, hydroxyacrylates, and multicomponent polymer matrices, which created by method of interpenetrating polymer networks. Particular attention is paid to description of synthesized and investigated nanocomposites based on polyurethane / poly (2-hydroxyethyl methacrylate) polymer matrix and nanooxides modified by biologically active compounds.

Polymeric Nanoparticles-Loaded Hydrogels for Biomedical Applications: A Systematic Review on In Vivo Findings

Clinically available medications face several hurdles that limit their therapeutic activity, including restricted access to the target tissues due to biological barriers, low bioavailability, and poor pharmacokinetic properties. Drug delivery systems (DDS), such as nanoparticles (NPs) and hydrogels, have been widely employed to address these issues. Furthermore, the DDS improves drugs’ therapeutic efficacy while reducing undesired side effects caused by the unspecific distribution over the different tissues. The integration of NPs into hydrogels has emerged to improve their performance when compared with each DDS individually. The combination of both DDS enhances the ability to deliver drugs in a localized and targeted manner, paired with a controlled and sustained drug release, resulting in increased drug therapeutic effectiveness. With the incorporation of the NPs into hydrogels, it is possible to apply the DDS locally and then provide a sustained release of the NPs in the site of action, allowing the drug uptake in the required location. Additionally, most of the materials used to produce the hydrogels and NPs present low toxicity. This article provides a systematic review of the polymeric NPs-loaded hydrogels developed for various biomedical applications, focusing on studies that present in vivo data.

A Universal Strategy for Growing a Tenacious Hydrogel Coating from a Sticky Initiation Layer

Controllably coating the surfaces of substrates/medical devices with hydrogels exhibits great application potential, but lacks universal techniques. Herein, a new method, namely ultraviolet-triggered surface catalytically initiated radical polymerization (UV-SCIRP) from a sticky initiation layer (SIL) (SIL@UV-SCIRP), is proposed for growing hydrogel coatings. The method involves three key steps: 1) depositing a sticky polydopamine/Fe³⁺ coating on the surface of the substrates-SIL, 2) reducing Fe³⁺ ions to Fe²⁺ ions as active catalysts by UV illumination with the assistance of citric acid, and 3) conducting SCIRP in a monomer solution at room temperature for growing hydrogel coatings. In this manner, practically any substrate's surface (natural or artificial materials) can be modified by hydrogel coatings with controllable thickness and diverse compositions. The hydrogel coatings exhibit good interface bonding with the substrates and enable easy changes in their wettability and lubrication performances. Importantly, this novel method facilitates the smooth growth of uniform hydrogel lubrication coatings on the surface of a range of medical devices with complex geometries. Finally, as a proof-of-concept, the slippery balls coated with hydrogel exhibited smooth movement within the catheter and esophagus. Hence, this method can prove to be a pioneering universal modification tool, especially in surface/interface science and engineering.

Advances in Copper-Based Biomaterials With Antibacterial and Osteogenic Properties for Bone Tissue Engineering

Treating bone defects coupled with pathogen infections poses a formidable challenge to clinical medicine. Thus, there is an urgent need to develop orthopedic implants that provide excellent antibacterial and osteogenic properties. Of the various types, copper-based biomaterials capable of both regenerating bone and fighting infections are an effective therapeutic strategy for bone tissue engineering and therefore have attracted significant research interest. This review examines the advantages of copper-based biomaterials for biological functions and introduces these materials’ antibacterial mechanisms. We summarize current knowledge about the application of copper-based biomaterials with antimicrobial and osteogenic properties in the prevention and treatment of bone infection and discuss their potential uses in the field of orthopedics. By examining both broad and in-depth research, this review functions as a practical guide to developing copper-based biomaterials and offers directions for possible future work.

Trace determination of antifungal drugs in biological fluids through a developed approach of hydrogel-based spin-column micro-solid-phase extraction followed by LC-MS/MS analysis

In the present research, a blended polyacrylamide-chitosan hydrogel was synthesized. For the first time, the prepared sorbent was efficiently employed in a hydrogel-based spin-column setup as a promising format. The proposed method was applied for monitoring the trace amounts of ketoconazole, clotrimazole, and miconazole in blood samples. Effective adsorption and desorption parameters were optimized using a central composite design and the one-variable-at-a-time method. Under the optimal conditions, the calibration curves were linear in the range of 15.0-1000.0, 1.0-1000.0, and 2.0-1000.0 ng mL^-1 for ketoconazole, clotrimazole, and miconazole, respectively, along with intra- and interday precision less than 8.4%. Limits of detection were obtained between 0.2 and 5.0 ng mL^-1 . The preconcentration factors were found in the range of 5.9-7.8. The introduced method was successfully applied for micro-solid-phase extraction of trace amounts of target antifungal drugs in blood samples, followed by liquid chromatography-tandem mass spectrometry. Satisfactory relative recoveries of 94.5-103.5% were obtained, implying method reliability. Overall, the proposed method provides good accuracy and repeatability, high reusability, and good applicability to determine antifungal drugs in complex biological matrices.

Nitric oxide releasing nanofibrous Fmoc-dipeptide hydrogels for amelioration of renal ischemia/reperfusion injury

Renal ischemia/reperfusion (I/R) injury is responsible for significant mortality and morbidity during renal procedures. Nitric oxide (NO) deficiency is known to play a crucial role in renal I/R injury; however, low stability and severe toxicity of high concentrations of NO have limited its applications. Herein, we developed an in-situ forming Fmoc-dipheylalanine hydrogel releasing s-nitroso-n-acetylpenicillamine (FmocFF-SNAP) for renal I/R injury. Fmoc-FF hydrogel comprising of β-sheet nanofibers was prepared through the pH-titration method. It was then characterized by electron microscopy, pyrene assay, and circular dichroism techniques. Mechanical properties of Fmoc-FF hydrogel (thixotropy and syringeability) were investigated by oscillatory rheology and texture analysis. To assess the therapeutic efficiency in the renal I/R injury model, expression of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) was measured in various samples (different concentrations of free SNAP and FmocFF-SNAP, unloaded Fmoc-FF, and sham control) by real-time RT-PCR, ROS production, serum biomarkers, and histopathological evaluations. According to the results, Fmoc-FF self-assembly in physiologic conditions led to the formation of an entangled nanofibrous and shear-thinning hydrogel. FmocFF-SNAP exhibited a sustained NO release over 7 days in a concentration-dependent manner. Importantly, intralesional injection of FmocFF-SNAP caused superior recovery of renal I/R injury when compared to free SNAP in terms of histopathological scores and renal function indices (e.g. serum creatinine, and blood urea nitrogen). Compared to the I/R control group, biomarkers of oxidative stress and iNOS expression were significantly reduced possibly due to the sustained release of NO. Interestingly, the eNOS expression showed a significant enhancement reflecting the regeneration of the injured endothelial tissue. Thus, the novel FmocFF-SNAP can be recommended for the alleviation of renal I/R injury.

An Overview of Engineered Hydrogel-Based Biomaterials for Improved β-Cell Survival and Insulin Secretion

Islet transplantation provides a promising strategy in treating type 1 diabetes as an autoimmune disease, in which damaged β-cells are replaced with new islets in a minimally invasive procedure. Although islet transplantation avoids the complications associated with whole pancreas transplantations, its clinical applications maintain significant drawbacks, including long-term immunosuppression, a lack of compatible donors, and blood-mediated inflammatory responses. Biomaterial-assisted islet transplantation is an emerging technology that embeds desired cells into biomaterials, which are then directly transplanted into the patient, overcoming the aforementioned challenges. Among various biomaterials, hydrogels are the preferred biomaterial of choice in these transplants due to their ECM-like structure and tunable properties. This review aims to present a comprehensive overview of hydrogel-based biomaterials that are engineered for encapsulation of insulin-secreting cells, focusing on new hydrogel design and modification strategies to improve β-cell viability, decrease inflammatory responses, and enhance insulin secretion. We will discuss the current status of clinical studies using therapeutic bioengineering hydrogels in insulin release and prospective approaches.

Real-Time NMR Monitoring of Spatially Segregated Enzymatic Reactions in Multilayered Hydrogel Assemblies*

Compartmentalized chemical reactions at the microscale are important in biotechnology, yet monitoring the molecular content at these small scales is challenging. To address this challenge, we integrate a compact, reconfigurable reaction cell featuring electrochemical functionality with high‐resolution NMR spectroscopy. We demonstrate the operation of this system by monitoring the activity of enzymes immobilized in chemically distinct layers within a multi‐layered chitosan hydrogel assembly. As a benchmark, we observed the parallel activities of urease (Urs), catalase (Cat), and glucose oxidase (GOx) by monitoring reagent and product concentrations in real‐time. Simultaneous monitoring of an independent enzymatic process (Urs) together with a cooperative process (GOx + Cat) was achieved, with chemical conversion modulation of the GOx + Cat process demonstrated by varying the order in which the hydrogel was assembled.

From Supramolecular Hydrogels to Multifunctional Carriers for Biologically Active Substances

Supramolecular hydrogels are 3D, elastic, water-swelled materials that are held together by reversible, non-covalent interactions, such as hydrogen bonds, hydrophobic, ionic, host-guest interactions, and metal-ligand coordination. These interactions determine the hydrogels' unique properties: mechanical strength; stretchability; injectability; ability to self-heal; shear-thinning; and sensitivity to stimuli, e.g., pH, temperature, the presence of ions, and other chemical substances. For this reason, supramolecular hydrogels have attracted considerable attention as carriers for active substance delivery systems. In this paper, we focused on the various types of non-covalent interactions. The hydrogen bonds, hydrophobic, ionic, coordination, and host-guest interactions between hydrogel components have been described. We also provided an overview of the recent studies on supramolecular hydrogel applications, such as cancer therapy, anti-inflammatory gels, antimicrobial activity, controlled gene drug delivery, and tissue engineering.

Crosslinking Strategies for the Microfluidic Production of Microgels

This article provides a systematic review of the crosslinking strategies used to produce microgel particles in microfluidic chips. Various ionic crosslinking methods for the gelation of charged polymers are discussed, including external gelation via crosslinkers dissolved or dispersed in the oil phase; internal gelation methods using crosslinkers added to the dispersed phase in their non-active forms, such as chelating agents, photo-acid generators, sparingly soluble or slowly hydrolyzing compounds, and methods involving competitive ligand exchange; rapid mixing of polymer and crosslinking streams; and merging polymer and crosslinker droplets. Covalent crosslinking methods using enzymatic oxidation of modified biopolymers, photo-polymerization of crosslinkable monomers or polymers, and thiol-ene “click” reactions are also discussed, as well as methods based on the sol−gel transitions of stimuli responsive polymers triggered by pH or temperature change. In addition to homogeneous microgel particles, the production of structurally heterogeneous particles such as composite hydrogel particles entrapping droplet interface bilayers, core−shell particles, organoids, and Janus particles are also discussed. Microfluidics offers the ability to precisely tune the chemical composition, size, shape, surface morphology, and internal structure of microgels by bringing multiple fluid streams in contact in a highly controlled fashion using versatile channel geometries and flow configurations, and allowing for controlled crosslinking.

Multifunctional Hydrogel Nanocomposites for Biomedical Applications

Hydrogels are used for various biomedical applications due to their biocompatibility, capacity to mimic the extracellular matrix, and ability to encapsulate and deliver cells and therapeutics. However, traditional hydrogels have a few shortcomings, especially regarding their physical properties, thereby limiting their broad applicability. Recently, researchers have investigated the incorporation of nanoparticles (NPs) into hydrogels to improve and add to the physical and biochemical properties of hydrogels. This brief review focuses on papers that describe the use of nanoparticles to improve more than one property of hydrogels. Such multifunctional hydrogel nanocomposites have enhanced potential for various applications including tissue engineering, drug delivery, wound healing, bioprinting, and biowearable devices.

Development of polymeric films embedded with liquid nanodomains

Modified microemulsions (MEs), termed by us nanodomains (NDs), seem to be suitable vehicles for dermal drug delivery due to their high surface area and the interface enriched with membrane recognizing agents, penetration enhancers, and other components. However, liquid nanodomains do not provide a controlled release of the bioactive through the skin. Therefore, the main goal of our present study is to develop a film polymeric platform embedded with liquid nanovehicles for the controlled release of drugs. This study provides a fundamental understanding of the main challenges of the preparation of special films capable of embedding nanodomains without destroying them. We describe film formation from "nanodomains destructive polymers" causing coalescence of the nanodroplets followed by structural failure compared to the formation from "constructive polymer" leading to the homogeneous, transparent films with a high loading capacity of nanodomains (up to 90 wt%). Using various fundamental structural techniques, we found that the film-forming process and its redissolution suggest the reconstitution of nanodomains with original structure and similar droplet size diameter ca. 12 nm. Additionally, thermal behavior studies demonstrated that the film does not have "free" or "bulk" water compared to well-defined free water peaks in liquid nanodomains systems. The embedded film with drug-loaded nanodomains offers a significant advantage as a drug delivery platform for controlled release long-term therapy.

Delivery systems for enhancing oncolytic adenoviruses efficacy

Oncolytic adenovirus (OAds) has long been considered a promising biotherapeutic agent against various types of cancer owing to selectively replicate in and lyse cancer cells, while remaining dormant in healthy cells. In the last years, multiple (pre)clinical studies using genetic engineering technologies enhanced OAds anti-tumor effects in a broad range of cancers. However, poor targeting delivery, tropism toward healthy tissues, low-level expression of Ad receptors on tumor cells, and pre-existing neutralizing antibodies are major hurdles for systemic administration of OAds. Different vehicles have been developed for addressing these obstacles, such as stem cells, nanoparticles (NPs) and shielding polymers, extracellular vesicles (EVs), hydrogels, and microparticles (MPs). These carriers can enhance the therapeutic efficacy of OVs through enhancing transfection, circulatory longevity, cellular interactions, specific targeting, and immune responses against cancer. In this paper, we reviewed adenovirus structure and biology, different types of OAds, and the efficacy of different carriers in systemic administration of OAds.

Salecan-Clay Based Polymer Nanocomposites for Chemotherapeutic Drug Delivery Systems; Characterization and In Vitro Biocompatibility Studies

Salecan is a microbial polysaccharide suitable to obtain hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility properties. In this work, Salecan of different concentrations was introduced into polymethacrylic acid (PMAA) in the presence of clay to form novel semi synthetic hydrogel nanocomposites systems and loaded afterwards with doxorubicin (DOX). The physical-chemical characteristics of the nanocomposites systems and their effect on the viability, and morphology of MDBK (Madin-Darby bovine kidney), HT-29 human colorectal adenocarcinoma and Colo 205 human colon adenocarcinoma cell lines were investigated. DOX release from the nanocomposite systems, cell up-take and subsequent effect on cell proliferation was also analyzed. It was found that Salecan concentration determined the swelling behavior, structural parameters and morphological features of the nanocomposite systems. The hydrogen bonds strongly influenced the formation of PMAA-Salecan-clay systems, each component bringing its own contribution, thus demonstrating the achievement of an advanced crosslinked network and a more compacted hydrogel nanocomposite morphology. All the synthesized nanocomposites had negligible toxicity to normal MDBK cells and chemoresistent HT-29 cell line, whereas in the case of Colo 205 cells a decrease by 40% of the cell viability was obtained for the sample containing the highest amount of Salecan. This effect was correlated with the lowest pore size distribution leading to highest available specific surface area and entrapped amount of DOX which was further released from the nanocomposite sample. Corroborating all the data it can be suggested that the synthesized nanocomposites with Salecan and clay could be good candidates as vehicles for chemotherapeutic agents.

Boronate ester cross-linked PVA hydrogels for the capture and H2O2-mediated release of active fluorophores

A new set of PVA hydrogels were formed using the boronate ester fluorescent probe PF1 and the novel boronate fluorescent probe PT1 as the covalent crosslinkers. Treatment with aqueous H2O2 allowed triggered release of the fluorescent dye accompanied by complete dissolution of the hydrogel.