Swelling/deswelling of anionic copolymer gels

Evaluation of Opuntia-carrageenan superporous hydrogel (OPM-CRG SPH) as an effective biomaterial for drug release and tissue scaffold

The process of wound healing involves complex interplay of systems biology, dependent on coordination of various cell types, both intra and extracellular mechanisms, proteins, and signaling pathways. To enhance these interactions, drugs must be administered precisely and continuously, effectively regulating the intricate mechanisms involved in the body's response to injury. Controlled drug delivery systems (DDS) play a pivotal role in achieving this objective. A proficient DDS shields the wound from mechanical, oxidative, and enzymatic stress, against bacterial contamination ensuring an adequate oxygen supply while optimizing the localized and sustained delivery of drugs to target tissue. A pH-sensitive SPH was designed by blending two natural polysaccharides, Opuntia mucilage and carrageenan, using microwave irradiation and optimized according to swelling index at pH 1.2, 7.0, and 8.0 and % porosity. Optimized grade was analyzed for surface hydrophilicity-hydrophobicity using OCA. Analytical characterizations were performed using FTIR, TGA, XRD, DSC, reflecting semicrystalline behavior. Mechanical property confirmed adequate strength. In vitro drug release study with ciprofloxacin-HCL as model drug showed 97.8 % release within 10 h, fitting to the Korsmeyer-Peppas model following diffusion and erosion mechanism. In vitro antimicrobial, anti-inflammatory assays, zebrafish toxicity, and animal studies in mice with SPH concluded it as a novel biomaterial.

Temperature-Sensitive Hydrogels as Carriers for Modulated Delivery of Acetaminophen

The purposes of this study are the polymerization of temperature-sensitive copolymers based on N-isopropyl acrylamide and 10 mol % of 2-hydroxypropylmethacrylate, characterisations of their thermal, morphological and swelling properties, as well as the analysis of potential application in drug-delivery systems. Acetaminophen, the representative of non-steroidal anti-inflammatory drugs, was used as a model drug in this study. It is a common pain relief drug, which is also used for fever treatment. However, oral administration comes with certain health risks, mainly the overdose and frequent administration of up to four times a day. The goal of applying temperature-sensitive hydrogel is to enable extended administration once a day, depending on the body temperature. The swelling behavior of the obtained poly(N-isopropyl acrylamide-co-2-hydroxypropylmethacrylate) (p(NIPA/HPMA)) hydrogels and their temperature-sensitivity, kinetics and order of swelling processes at 18 and 38 °C were analyzed. The thermal properties of these hydrogels were observed by the DSC method, and the obtained thermograms showed both melting and glass transitions. The drug delivery system of p(NIPA/HPMA) hydrogels with loaded acetaminophen was analyzed using scanning electron microscopy and Fourier transform infrared spectroscopy methods. Structural analysis of FTIR spectra indicates that non-covalent intermolecular interactions of the type of hydrogen bonds were formed among functional groups of acetaminophen and side-chains of p(NIPA/HPMA) hydrogels. The surface structure of p(NIPA/HPMA) hydrogels after drug loading indicates the acetaminophen presence into the pores of the hydrogel network, and their loading efficiency was higher than 92%. Qualitative and quantitative analysis of acetaminophen, determined by the high-pressure liquid chromatography method, showed that about 90-99% of the loaded amount was released from p(NIPA/HPMA) hydrogels within 24 h. Kinetic parameters of the acetaminophen release under simulated gastrointestinal conditions were determined. Based on obtained results, the drug delivery system of temperature-sensitive p(NIPA/HPMA) hydrogels with loaded acetaminophen could be suitable for additional investigation for modulated drug administration, e.g., for extended drug administration.

Enzyme-Triggered l-α/d-Peptide Hydrogels as a Long-Acting Injectable Platform for Systemic Delivery of HIV/AIDS Drugs

Eradicating HIV/AIDS by 2030 is a central goal of the World Health Organization. Patient adherence to complicated dosage regimens remains a key barrier. There is a need for convenient long-acting formulations that deliver drugs over sustained periods. This paper presents an alternative platform, an injectable in situ forming hydrogel implant to deliver a model antiretroviral drug (zidovudine [AZT]) over 28 days. The formulation is a self-assembling ultrashort d or l-α peptide hydrogelator, namely phosphorylated (naphthalene-2-ly)-acetyl-diphenylalanine-lysine-tyrosine-OH (NapFFKY[p]-OH), covalently conjugated to zidovudine via an ester linkage. Rheological analysis demonstrates phosphatase enzyme instructed self-assembly, with hydrogels forming within minutes. Small angle neutron scattering data suggest hydrogels form narrow radius (≈2 nm), large length fibers closely fitting the flexible cylinder elliptical model. d-Peptides are particularly promising for long-acting delivery, displaying protease resistance for 28 days. Drug release, via hydrolysis of the ester linkage, progress under physiological conditions (37 °C, pH 7.4, H2 O). Subcutaneous administration of Napffk(AZT)Y[p]G-OH in Sprague Dawley rats demonstrate zidovudine blood plasma concentrations within the half maximal inhibitory concentration (IC50 ) range (30-130 ng mL-1 ) for 35 days. This work is a proof-of-concept for the development of a long-acting combined injectable in situ forming peptide hydrogel implant. These products are imperative given their potential impact on society.

Preparation of multifunctional hydrogels with accessible isothiouronium groups via radical cross-linking copolymerization

Hydrogels can be equipped with functional groups for specific purposes. Isothiouronium groups can enhance adsorptivity, or allow coupling of other functional groups through mild reactions after transformation to thiol groups. Here we present a method to prepare multifunctional hydrogels by introducing isothiouronium groups into poly(ethylene glycol) diacrylate (PEGDA) hydrogels, and convert them into thiol-functionalized hydrogels by the reduction of the isothiouronium groups. For this purpose, the amphiphilic monomer 2-(11-(acryloyloxy)-undecyl)isothiouronium bromide (AUITB), containing an isothiouronium group, was synthesized and copolymerized with PEGDA. In this convenient way, it was possible to incorporate up to 3 wt% AUITB into the hydrogels without changing their equilibrium swelling degree. The successful functionalization was demonstrated by surface analysis of the hydrogels with water contact angle measurements and increased isoelectric points of the hydrogel surfaces from 4.5 to 9.0 due to the presence of the isothiouronium groups. The hydrogels showed a suitability as an adsorbent, as exemplified by the pronounced adsorption of the anionic drug diclofenac. The potential of the functionalization for (bio)conjugation reactions was demonstrated by the reduction of isothiouronium groups to thiols and subsequent immobilization of the functional enzyme horseradish peroxidase on the hydrogels. The results show that fully accessible isothiouronium groups can be introduced into radically cross-linked hydrogels.

3D Bioprinting of Hyaline Articular Cartilage: Biopolymers, Hydrogels, and Bioinks

The musculoskeletal system, consisting of bones and cartilage of various types, muscles, ligaments, and tendons, is the basis of the human body. However, many pathological conditions caused by aging, lifestyle, disease, or trauma can damage its elements and lead to severe disfunction and significant worsening in the quality of life. Due to its structure and function, articular (hyaline) cartilage is the most susceptible to damage. Articular cartilage is a non-vascular tissue with constrained self-regeneration capabilities. Additionally, treatment methods, which have proven efficacy in stopping its degradation and promoting regeneration, still do not exist. Conservative treatment and physical therapy only relieve the symptoms associated with cartilage destruction, and traditional surgical interventions to repair defects or endoprosthetics are not without serious drawbacks. Thus, articular cartilage damage remains an urgent and actual problem requiring the development of new treatment approaches. The emergence of biofabrication technologies, including three-dimensional (3D) bioprinting, at the end of the 20th century, allowed reconstructive interventions to get a second wind. Three-dimensional bioprinting creates volume constraints that mimic the structure and function of natural tissue due to the combinations of biomaterials, living cells, and signal molecules to create. In our case-hyaline cartilage. Several approaches to articular cartilage biofabrication have been developed to date, including the promising technology of 3D bioprinting. This review represents the main achievements of such research direction and describes the technological processes and the necessary biomaterials, cell cultures, and signal molecules. Special attention is given to the basic materials for 3D bioprinting-hydrogels and bioinks, as well as the biopolymers underlying the indicated products.

pH-Sensitive Hybrid System Based on Eu3+/Gd3+ Co-Doped Hydroxyapatite and Mesoporous Silica Designed for Theranostic Applications

Nanomaterials such as pH-responsive polymers are promising for targeted drug delivery systems, due to the difference in pH between tumor and healthy regions. However, there is a significant concern about the application of these materials in this field due to their low mechanical resistance, which can be attenuated by combining these polymers with mechanically resistant inorganic materials such as mesoporous silica nanoparticles (MSN) and hydroxyapatite (HA). Mesoporous silica has interesting properties such as high surface area and hydroxyapatite has been widely studied to aid in bone regeneration, providing special properties adding multifunctionality to the system. Furthermore, fields of medicine involving luminescent elements such as rare earth elements are an interesting option in cancer treatment. The present work aims to obtain a pH-sensitive hybrid system based on silica and hydroxyapatite with photoluminescent and magnetic properties. The nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption methods, CHN elemental analysis, Zeta Potential, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), vibrational sample magnetometry (VSM), and photoluminescence analysis. Incorporation and release studies of the antitumor drug doxorubicin were performed to evaluate the potential use of these systems in targeted drug delivery. The results showed the luminescent and magnetic properties of the materials and showed suitable characteristics for application in the release of pH-sensitive drugs.

Swelling of Homogeneous Alginate Gels with Multi-Stimuli Sensitivity

A new two-step method is suggested for the preparation of homogeneous alginate gels. In the first step, alginate chains are weakly bonded by Ca2+ ions in an aqueous solution with a low pH. In the next step, the gel is immersed into a strong solution of CaCl2 to finalize the cross-linking process. Homogeneous alginate gels preserve their integrity in aqueous solutions with a pH ranging from 2 to 7 and ionic strength in the interval from 0 to 0.2 M, at temperatures ranging from room temperature up to 50 °C, and can be used in biomedical applications. The immersion of these gels into aqueous solutions with low pH induces the partial breakage of ionic bonds between chains (treated as gel degradation). This degradation affects the equilibrium and transient swelling of homogeneous alginate gels and makes them sensitive to the history of loading and environmental conditions (pH, ionic strength and temperature of aqueous solutions). As sensitivity to the environmental stimuli is a characteristic feature of polymer networks connected by catch bonds, homogeneous alginate gels may serve as a simple model, mimicking the behavior of more sophisticated structures in living matter.

Biomedical Applications of Thermosensitive Hydrogels for Controlled/Modulated Piroxicam Delivery

The objectives of this study are the synthesis of thermosensitive poly(N-isopropylacrylamide-co-2-hydroxypropyl methacrylate), p(NiPAm-HPMet), hydrogels and the analysis of a drug-delivery system based on piroxicam, as a model drug, and synthesized hydrogels. A high pressure liquid chromatography method has been used in order to determine both qualitative and quantitative amounts of unreacted monomers and crosslinkers from polymerized hydrogels. Swelling kinetics and the order of a swelling process of the hydrogels have been analyzed at 10 and 40 °C. The copolymers' thermal properties have been monitored by the differential scanning calorimetry (DSC) method. DSC termograms have shown that melting occurs in two temperature intervals (142.36-150.72 °C and 153.14-156.49 °C). A matrix system with incorporated piroxicam has been analyzed by using FTIR and SEM methods. Structural analysis has demonstrated that intermolecular non-covalent interactions have been built between side-groups of copolymer and loaded piroxicam. Morphology of p(NiPAm-HPMet) after drug incorporation indicates the piroxicam presence into the copolymer pores. Kinetic parameters of the piroxicam release from hydrogels at 37 °C and pH 7.4 indicate that the fluid transport mechanism corresponds to Fickian diffusion. As a result, formulation of thermosensitive p(NiPAm-HPMet) hydrogels with incorporated piroxicam could be of interest for further testing as a drug carrier for modulated and prolonged release, especially for topical administration.

Sodium Alginate-g-acrylamide/acrylic Acid Hydrogels Obtained by Electron Beam Irradiation for Soil Conditioning

Being both a cause and a victim of water scarcity and nutrient deficiency, agriculture as a sustainable livelihood is dependent now on finding new suport solutions. Biodegradable hydrogels usage as soil conditioners may be one of the most effective solutions for irrigation efficiency improvement, reducing the quantity of soluble fertilizers per crop cycle and combating pathogens, due to their versatility assured by both obtaining method and properties. The first goal of the work was the obtaining by electron beam irradiation and characterization of some Sodium Alginate-g-acrylamide/acrylic Acid hydrogels, the second one being the investigation of their potential use as a soil conditioner by successive experiments of absorption and release of two different aqueous nutrient solutions. Alginate-g-acrylamide/acrylic Acid hydrogels were obtained by electron beam irradiation using the linear accelerator ALID 7 at 5.5 MeV at the irradiation doses of 5 and 6 kGy. For this were prepared monomeric solutions that contained 1 and 2% sodium alginate, acrylamide and acrylic acid in ratios of 1:1 and 1.5:1, respectively, for the obtaining of materials with hybrid properties derived from natural and synthetic components. Physical, chemical, structural and morphological characteristics of the obtained hydrogels were investigated by specific analysis using swelling, diffusion and network studies and Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Four successive absorption and release experiments of some synthetic and natural aqueous solutions with nutrients were performed.

Carbopol Based Hydrogels for ITOPRIDE Hydrochloride Delivery; Synthesis, Characterization and Comparative Assessment with Various Monomers

The objective of the current study was to synthesize and characterize carbopol containing hydrogels with different monomers such as methacrylic acid (MAA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and itaconic acid (ITA). Free radical polymerization method was optimized for the preparation of different formulations using N,N-methylene bis-acrylamide (MBA) as cross linking agent. Different studies were performed to evaluate the effect of different monomers on swelling, drug loading and drug release. Itopride Hydrochloride was used as model drug. FTIR, TGA, DSC and SEM were performed to probe the characteristics of fabricated hydrogels. Swelling studies of different fabricated hydrogels were performed in three pH conditions (1.2, 4.5 & 6.8). Higher swelling was observed at pH 6.8. An in-vitro release study was performed on pH 1.2 and 6.8. The synthesized hydrogels exhibited excellent mechanical strength, higher drug loading, pH sensitive and time dependent release up to 30 h. The excellent mechanical strength and extended drug release of Carbopol-co-poly-MAA-ITA hydrogels make them a potential candidate for controlled delivery of Itopride hydrochloride.

Alginate Particles for Encapsulation of Phenolic Extract from Spirulina sp. LEB-18: Physicochemical Characterization and Assessment of In Vitro Gastrointestinal Behavior

Encapsulation can be used as a strategy to protect and control the release of bioactive extracts. In this work, an extract from Spirulina sp. LEB-18, rich in phenolic compounds, was encapsulated in biopolymeric particles (i.e., composed of alginate) and characterized concerning their thermal behavior using differential scanning calorimetry (DSC), size, morphology, swelling index (S), and encapsulation efficiency (EE%); the release profile of the phenolic compounds at different pHs and the particle behavior under in vitro gastrointestinal digestion were also evaluated. It was shown that it is possible to encapsulate the phenolic extract from Spirulina sp. LEB-18 in alginate particles with high encapsulation efficiency (88.97%). It was also observed that the particles are amorphous and that the encapsulated phenolic compounds were released at a pH 7.2 but not at pH 1.5, which means that the alginate particles are able to protect the phenolic compounds from the harsh stomach conditions but lose their integrity under intestinal pH conditions. Regarding bioaccessibility, it was observed that the encapsulated phenolic compounds showed higher bioaccessibility compared to phenolic compounds in free form. This work increases the knowledge about the behavior of alginate particles encapsulating phenolic compounds during in vitro gastrointestinal digestion. It also provides essential information for designing biopolymeric particle formulations encapsulating phenolic compounds for application in pharmaceutical and food products.

Physicomechanical and Morphological Characterization of Multi-Structured Potassium-Acrylate-Based Hydrogels

In this work, a photo-polymerization route was used to obtain potassium acrylate-co-acrylamide hydrogels with enhanced mechanical properties, well-defined microstructures in the dry state, and unique meso- and macrostructures in the hydrated state. The properties of the hydrogels depended on the concentration of the crosslinking agent. Mechanical properties, swelling capacity, and morphology were analyzed, showing a well-defined transition at a critical concentration of the crosslinker. In terms of morphology, shape-evolving surface patterns appeared at different scales during swelling. These surface structures had a noticeable influence on the mechanical properties. Hydrogels with structures exhibited better mechanical properties compared to unstructured hydrogels. The critical crosslinking concentration reported in this work (using glycerol diacrylate) is a reference point for the future preparation of multistructured acrylic hydrogel with enhanced properties.

Challenges in delivering therapeutic peptides and proteins: A silk-based solution

Peptide- and protein-based therapeutics have drawn significant attention over the past few decades for the treatment of infectious diseases, genetic disorders, oncology, and many other clinical needs. Yet, protecting peptide- and protein-based drugs from degradation and denaturation during processing, storage and delivery remain significant challenges. In this review, we introduce the properties of peptide- and protein-based drugs and the challenges associated with their stability and delivery. Then, we discuss delivery strategies using synthetic polymers and their advantages and limitations. This is followed by a focus on silk protein-based materials for peptide/protein drug processing, storage, and delivery, as a path to overcome stability and delivery challenges with current systems.

Characterization of a Centrifugal Microfluidic Orthogonal Flow Platform

To bring to bear the power of centrifugal microfluidics on vertical flow immunoassays, control of flow orthogonally through nanoporous membranes is essential. The on-disc approach described here leverages the rapid print-cut-laminate (PCL) disc fabrication and prototyping method to create a permanent seal between disc materials and embedded nanoporous membranes. Rotational forces drive fluid flow, replacing capillary action, and complex pneumatic pumping systems. Adjacent microfluidic features form a flow path that directs fluid orthogonally (vertically) through these embedded membranes during assay execution. This method for membrane incorporation circumvents the need for solvents (e.g., acetone) to create the membrane-disc bond and sidesteps issues related to undesirable bypass flow. In other recently published work, we described an orthogonal flow (OF) platform that exploited embedded membranes for automation of enzyme-linked immunosorbent assays (ELISAs). Here, we more fully characterize flow patterns and cellulosic membrane behavior within the centrifugal orthogonal flow (cOF) format. Specifically, high-speed videography studies demonstrate that sample volume, membrane pore size, and ionic composition of the sample matrix significantly impact membrane behavior, and consequently fluid drainage profiles, especially when cellulosic membranes are used. Finally, prototype discs are used to demonstrate proof-of-principle for sandwich-type antigen capture and immunodetection within the cOF system.

One-Step Fabrication of Hollow Spherical Cellulose Beads: Application in pH-Responsive Therapeutic Delivery

The path to greater sustainability and the development of polymeric drug delivery systems requires innovative approaches. The adaptation and use of biobased materials for applications such as targeted therapeutic delivery is, therefore, in high demand. A crucial part of this relates to the development of porous and hollow structures that are biocompatible, pH-responsive, deliver active substances, and contribute to pain relief, wound healing, tissue regeneration, and so forth. In this study, we developed a facile single-step and water-based method for the fabrication of hollow spherical cellulose beads for targeted drug release in response to external pH stimuli. Through base-catalyzed deprotection, hydrophobic solid and spherical cellulose acetate beads are transformed into hydrophilic cellulose structures with a hollow interior (wall thickness: 150 μm and inner diameter: 650 μm) by a stepwise increment of temperature and treatment time. Besides the pH-responsive fluid uptake properties, the hollow cellulose structures exhibit a maximum encapsulation efficiency of 20-85% diclofenac (DCF), a nonsteroidal anti-inflammatory drug, used commonly to treat pain and inflammatory diseases. The maximum amount of DCF released in vitro increased from 20 to 100% when the pH of the release medium increased from pH 1.2 to 7.4. As for the DCF release patterns and kinetic models at specific pH values, the release showed a diffusion- and swelling-controlled profile, effortlessly fine-tuned by external environmental pH stimuli. Overall, we show that the modified beads exhibit excellent characteristics for transport across the gastrointestinal tract and enhance the bioavailability of the drug. Their therapeutic efficacy and biocompatibility are also evident from the studies on human fibroblast cells. We anticipate that this platform could support and inspire the development of novel sustainable and effective polysaccharide-based delivery systems.

A chitosan hydrogel sealant with self-contractile characteristic: From rapid and long-term hemorrhage control to wound closure and repair

Emergent and long-term hemorrhage control is requisite and beneficial for reducing global mortality and postoperative complications (e.g., second bleeding and adverse tissue adhesion). Despite recent advance in injectable hydrogels for hemostasis, achieving rapid gelation, strong tissue-adhesive property and stable mechanical strength under fluid physiological environment is still challenging. Herein, we developed a novel chitosan hydrogel (CCS@gel) via dynamic Schiff base reaction and mussel-inspired catechol chemistry. The hydrogel possessed high gelation rate (<10 s), strong wet adhesiveness, excellent self-healing performance and biocompatibility. More importantly, the CCS@gel exhibited saline-induced contractile performance and mechanical enhancement, promoting its mechanical property in moist internal conditions. In vivo studies demonstrated its superior hemostatic efficacy for diverse anticoagulated visceral and carotid bleeding scenarios, compared to commercialized fibrin glue. The hydrogel-treated rats survived for 8 weeks with minimal inflammation and postoperative adhesion. These results revealed that the promising CCS@gel would be a facile, efficient and safe sealant for clinical hemorrhage control.

Injectable chitosan/collagen hydrogels nano-engineered with functionalized single wall carbon nanotubes for minimally invasive applications in bone

Mechanical robustness is an essential consideration in the development of hydrogel platforms for bone regeneration, and despite significant advances in the field of injectable hydrogels, many fail in this regard. Inspired by the mechanical properties of carboxylated single wall carbon nanotubes (COOH-SWCNTs) and the biological advantages of natural polymers, COOH-SWCNTs were integrated into chitosan and collagen to formulate mechanically robust, injectable and thermoresponsive hydrogels with interconnected molecular structure for load-bearing applications. This study presents a complete characterisation of the structural and biological properties, and mechanism of gelation of these novel formulated hydrogels. Results demonstrate that β-glycerophosphate (β-GP) and temperature play important roles in attaining gelation at physiological conditions, and the integration with COOH-SWCNTs significantly changed the structural morphology of the hydrogels to a more porous and aligned network. This led to a crystalline structure and significantly increased the mechanical strength of the hydrogels from kPa to MPa, which is closer to the mechanical strength of the bone. Moreover, increased osteoblast proliferation and rapid adsorption of hydroxyapatite on the surface of the hydrogels indicates increased bioactivity with addition of COOH-SWCNTs. Therefore, these nano-engineered hydrogels are expected to have wide utility in the area of bone tissue engineering and regenerative medicine.

Alginate/poloxamer hydrogel obtained by thiol-acrylate photopolymerization for the alleviation of the inflammatory response of human keratinocytes

Hydrogel-based wound dressings have been intensively studied as promising materials for wound healing and care. The mixed-mode thiol-acrylate photopolymerization is used in this paper for alginate/poloxamer hydrogels formation. First, the alginate was modified with thiol groups using the esterification reaction with cysteamine, and second, the terminal hydroxyl groups of poloxamer were esterified with acryloyl chloride to introduce polymerizable acrylate groups. Finally, the cross-linking reaction between the two macromers was performed to produce degradable alginate/poloxamer hydrogels. The optimum conditions for the photo-initiated reaction were studied in order to obtain high gel fractions. The resulting hydrogels have high swelling capacity in simulated physiological conditions, good elasticity and strength, and appropriate porosity, some of the physico-chemical properties required for their applications as wound dressings/patches. The biological assays show that the alginate/poloxamer hydrogels induce proliferation of human keratinocyte and have an anti-inflammatory effect on lipopolysaccharides (LPS)-activated keratinocytes by inhibiting the extracellular signal-regulated kinases (ERK)/ nuclear factor (NF)-kB/ tumor necrosis factor (TNF)-α signalling pathway. Taken together, the results showed that the chemical cross-linked alginate/poloxamer hydrogels may function as a dressing/patch applied directly on the skin lesion to heal the wound by reducing the exacerbated inflammation, the main cause of wound healing delay and local infection.

A Robust Fabrication Technique for Hydrogel Films Containing Micropatterned Opal Structures via Micromolding and an Integrated Evaporative Deposition-Photopolymerization Approach

Opal-structured thin-film hydrogel materials with micropatterns hold great potential for utility in a wide range of sensing applications. Micropatterning offers key advantages such as ready addressability, high throughput assay, and multiplexing. However, controlled fabrication of such films in a rapid, inexpensive, and reliable manner remains a challenge. Existing techniques suffer from long opal deposition times and often involve complex and arduous steps. In this report, we examined a simple micromolding-based evaporation-polymerization method for the fabrication of poly(ethylene glycol)-based hydrogel films containing micropatterned opal structures. Specifically, intense and uniform opalescent colors were achieved by evaporative deposition of polystyrene bead solution in patterned micromolds. These opal micropatterns were then captured in hydrogel films by simple photopolymerization of a UV-curable PEG diacrylate solution. The as-prepared films show high tunability as well as responsiveness to various environmental cues readily manifested via shifts in color. Combined with UV-vis reflectance spectroscopy and scanning electron microscopy results, these findings illustrate the robust, simple, and reliable nature of our integrated deposition-polymerization approach for controlled fabrication of optically active and stimuli-responsive functional materials. We thus envision that the results and the facile approach reported here can be extended to many application areas including environmental monitoring, diagnostics, and biosensing applications.

Modified Biochanin A Release from Dual pH- and Thermo-Responsive Copolymer Hydrogels

The temperature- and pH-responsive poly(N-isopropylacrylamide-co-acrylic acid), p(NIPAM-co-AA), copolymer was synthesized by free radical polymerization and examined as a carrier for modified release of biochanin A. Biochanin A is a biologically active methoxylated isoflavone which exhibits estrogenic and other pharmacological activities. Due to its poor aqueous solubility and extensive first-pass metabolism, biochanin A has low bioavailability. The aim of this work was to incorporate biochanin A into the synthesized p(NIPAM-co-AA) copolymer and to examine its release at the body temperature and pH values that correspond to pH values of vaginal and rectal cavities. The amount of released biochanin A was monitored by the ultra-visible spectroscopy (UV-Vis) method. The structure of synthesized p(NIPAM-co-AA) copolymer and copolymer with incorporated biochanin A were characterized by using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. The content of residual monomers in the synthesized copolymer was analyzed by using the high-pressure liquid chromatography (HPLC) method. The swelling behavior of p(NIPAM-co-AA) copolymer was monitored in relation to the temperature and pH values of the surrounding medium. For modelling the process of p(NIPAM-co-AA) copolymer swelling, the full three-level factorial design was applied.

Semi-Crystalline Copolymer Hydrogels as Smart Drug Carriers: In Vitro Thermo-Responsive Naproxen Release Study

In this study, poly(N-isopropylacrylamide-co-2-hydroxypropyl methacrylate) hydrogels were synthesized using free radical initiated copolymerization method. Four hydrogels with different cross-linker concentrations were prepared. Semi-crystalline, cross-linked copolymer networks were confirmed by FTIR, SEM and XRD analysis. Variation of swelling behaviour was monitored gravimetrically and thermo-responsiveness has been noticed. An application of synthesized thermo-responsive hydrogels as carriers for the modulated release of anti-inflammatory model drug was investigated. Moreover, naproxen loading into these hydrogels was also determined using FTIR, SEM and XRD techniques and release was analyzed using HPLC method at simulated physiological conditions. Swelling kinetic and mechanism of water transport, as well as diffusion of naproxen through the hydrogels were analyzed. Thus, the aim of this work was to study various compositions of obtained hydrogels and their possibility of application as a thermo-responsive carrier for prolonged naproxen release in order to evaluate as a potential candidate for drug carrier in future pharmaceutical applications.

pH-Responsive "Smart" Hydrogel for Controlled Delivery of Silver Nanoparticles to Infected Wounds

Persistent wound infections have been a therapeutic challenge for a long time. Current treatment approaches are mostly based on the delivery of antibiotics, but these are not effective for all infections. Here, we report the development of a sensitive pH-responsive hydrogel that can provide controlled, pH-triggered release of silver nanoparticles (AgNPs). This delivery system was designed to sense the environmental pH and trigger the release of AgNPs when the pH changes from acidic to alkaline, as occurs due to the presence of pathogenic bacteria in the wound. Our results show that the prepared hydrogel restricts the release of AgNPs at acidic pH (pH = 4) but substantially amplifies it at alkaline pH (pH = 7.4 and pH = 10). This indicates the potential use of the hydrogel for the on-demand release of Ag+ depending on the environmental pH. In vitro antibacterial studies demonstrated effective elimination of both Gram-negative and positive bacteria. Additionally, the effective antibacterial dose of Ag+ showed no toxicity towards mammalian skin cells. Collectively, this pH-responsive hydrogel presents potential as a promising new material for the treatment of infected wounds.

In Vitro Synthesis of Branchless Linear (1 → 6)-α-d-Glucan by Glucosyltransferase K: Mechanical and Swelling Properties of Its Hydrogels Crosslinked with Diglycidyl Ethers

A hydrogel was prepared from a polysaccharide, enzymatically synthesized through a one-pot reaction in aqueous solution, and its properties as a functional material were evaluated. Enzymatic synthesis using glucosyltransferase K obtained from Streptococcus salivarius ATCC 25975 was performed with sucrose as a substrate. The synthetic product was unbranched linear (1 → 6)-α-d-glucan with a high molecular weight, M _w: 1.0-3.0 × 10⁵. The synthesized (1 → 6)-α-d-glucan was insoluble in water and crystallized in a monoclinic unit cell, which is consistent with the hydrated form of dextran. Transparent and highly swellable (1 → 6)-α-d-glucan hydrogels were obtained by crosslinking with diglycidyl ethers. The hydrogels showed no syneresis and no volume change during compression, resulting in the retention of shape under repeated compression. The elastic moduli of these hydrogels (<60 kPa) are smaller than those of other polysaccharide-based hydrogels having the same solid contents. The oven-dried gels could be restored to the hydrogel state with the original transparency and a recovery ratio greater than 98%. The mechanism of water diffusion into the hydrogel was investigated using the kinetic equation of Peppas. The properties of the hydrogel are impressive relative to those of other polysaccharide-based hydrogels, suggesting its potential as a functional biomaterial.

Rose Bengal Crosslinking to Stabilize Collagen Sheets and Generate Modulated Collagen Laminates

For medical application, easily accessible biomaterials with tailored properties are desirable. Collagen type I represents a biomaterial of choice for regenerative medicine and tissue engineering. Here, we present a simple method to modify the properties of collagen and to generate collagen laminates. We selected three commercially available collagen sheets with different thicknesses and densities and examined the effect of rose bengal and green light collagen crosslinking (RGX) on properties such as microstructure, swelling degree, mechanical stability, cell compatibility and drug release. The highest impact of RGX was measured for Atelocollagen, for which the swelling degree was reduced from 630% (w/w) to 520% (w/w) and thickness measured under force application increased from 0.014 mm to 0.455 mm, indicating a significant increase in mechanical stability. Microstructural analysis revealed that the sponge-like structure was replaced by a fibrous structure. While the initial burst effect during vancomycin release was not influenced by crosslinking, RGX increased cell proliferation on sheets of Atelocollagen and on Collagen Solutions. We furthermore demonstrate that RGX can be used to covalently attach different sheets to create materials with combined properties, making the modification and combination of readily available sheets with RGX an attractive approach for clinical application.

Advancements in Polymer and Lipid-based Nanotherapeutics for Cancer Drug Targeting

Cancer is a global disease. It is the second leading cause of death worldwide, according to the health report. Approximately 70% of deaths from cancer occurs in low- and middle-income countries. According to the WHO, in 2015 8.8 million deaths were reported due to cancer worldwide. The conventional system of medicine was used since a long for the management of the disease, but it comes with the drawback of low safety, less efficacy and non-targeting of cancer cells. Nanotherapeutics has become the most exploited drug targeting system based on the safety and efficacy this system provides over the conventional system. This review summarizes an advanced design consideration in anticancer therapy, recent advancements in the nanocarrier-based advanced drug targeting, challenges and limitations related to nanoparticles-based therapy in cancer and its future perspective. The review also lists the on-going clinical trials in the last five years on nano-based therapy for different types of cancer. The data for this article was obtained by an extensive literature review of related published scientific contents from the WHO's website, PubMed, Scopus, Scielo, clinicaltrials.gov and other relevant scientific archiving services. The safety and efficacy that nanoparticles provide, and the current research strongly support their application in cancer drug targeting. However, their presence in the market is still limited. Nanotherapeutics in cancer drug targeting needs extensive research in association with pharmaceutical industries. Nano-targeting based therapies are the future of pharmaceutical designing for the diagnosis, management and prevention of different forms of cancer.

Site-specific targeted drug delivery systems for the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis and manifests as a complex and dysregulated immune response. To date, there is no cure for IBD; thus, lifelong administration of maintenance drugs is often necessary. Since conventional IBD treatment strategies do not target the sites of inflammation, only limited efficacy is observed with their use. Moreover, the possibility of severe side effects resulting from systemic drug redistribution is high when conventional drug treatments are used. Therefore, a straightforward disease-targeted drug delivery system is desirable. Based on the pathophysiological changes associated with IBD, novel site-specific targeted drug delivery strategies that deliver drugs directly to the inflammation sites can enhance drug accumulation and decrease side effects. This review summarizes novel inflammation targeted delivery systems in the management of IBD. It also discusses the challenges and new perspectives in this field.

Single and binary ion sorption equilibria of monovalent and divalent ions in commercial ion exchange membranes

The co-ion and counter-ion sorption of monovalent (Na⁺, K⁺, Cl^- and NO₃^-) and divalent ions (Ca²⁺ and SO₄^2-) in commercial Neosepta ion exchange membranes were systemically studied in both single and binary salt systems. The new generation of Neosepta cation exchange membrane (CSE) showed a significant difference in water uptake and co-ion sorption compared to the earlier generation (CMX). Use of the Manning model confirmed that there were significant differences between these membranes, with the estimated value of the Manning parameter changing from 1.0 ± 0.1 for CMX to 2.8 ± 0.5 for CSE. There were fewer differences between the two Neosepta anion exchange membranes, AMX and ASE. In single salt solutions, potassium sorbed most strongly into the cation exchange membranes, but in binary salt mixtures, calcium dominated due to Donnan exclusion at low concentrations. While these trends were expected, the sorption behaviour in the anion exchange membranes was more complex. The water uptake of both AMX and ASE was shown to be the greatest in Na₂SO₄ solutions. This strong water uptake was reflected in strong sorption of sulphate ions in a single salt solution. Conversely, in a binary salt mixture with NaCl, sulphate sorption fell significantly at higher concentrations. This was possibly caused by ion pairing within the solution, as well as the strongly hydrophobic nature of styrene in the charged polymer. Water uptake was lowest in NaNO₃ solutions, even though sorption of the nitrate ion was comparable to that of chloride in these single salt solutions. In the binary mixture, nitrate was absorbed more strongly than chloride. These results could be due to the low surface charge density of this ion allowing it to bond more strongly with the hydrophobic polymeric backbone at the exclusion of water and other ions.

Ionotropic Gelation of Chitosan for Next-Generation Composite Proton Conducting Flat Structures

(1) Background: Ionotropic gelation of cost-effective and eco-friendly biopolymer chitosan (Chit) is a novel and promising approach to the one-step synthesis of proton-conducting fuel cell bio-membranes.The method discovered by the author in 2011 and subsequently drowned among very few papers. This work aimed to relaunch this method through clear and effective communication of new unpublished results emphasizing the key aspects of this topic for successful dissemination of the results and significant future developments. (2) Methods and results: The mechanism of in-situ ionotropic gelation of Chit on an alumina substrate by phosphotungtate anions (PWA3-) was discussed and analyzed. The study sheds light on the effect of prolonged post-treatment in phosphotungstic acid (PWA) solution on the obtained chitosan/phosphotungstate (Chit-PWA) flat structures. Methods used included combined structural (XRD), thermal-gravimetric (DTG), electrochemical (in-situ EIS), compositional (EDX),morphological analysis (SEM), as well as the performances in a low temperature H2/O2 fuel cell(4) Conclusions: This contribution discloses novel possibilities aimed at increasing the impact of ionotropic gelation of chitosan on the scientific community working on the synthesis of novel proton conductive bio-composite membranes and structures.

Okra (Hibiscus esculentus) gum based hydrophilic matrices for controlled drug delivery applications: Estimation of percolation threshold

This study aims to explore the potential of gum extracted from okra fruit (Hibiscus esculentus) in developing hydrophilic matrices for controlled drug release applications, including determination of its percolation threshold. Flurbiprofen (poorly soluble), theophylline (sparingly soluble) and metformin (freely soluble) were employed as model drugs and incorporated using direct compression into matrices containing 40% w/w of three drugs with different physicochemical properties. Atomic force microscopy was used to study the surface texture properties of developed matrices; the surfaces of the flurbiprofen-based matrices were comparatively rough most likely as a consequence of its poor compactability. Swelling studies found that the swelling rate increased as the concentration of okra gum was increased. However, for all matrices, an increase in the gum concentration resulted in decreased drug release. The estimated percolation threshold of the okra gum calculated was found in the region of ~25% v/v plus initial porosity. Knowing the percolation threshold will enable formulators to use the minimal amount of polymer for sustain release matrices thus the controlling costs and maximising the sustainable potential of okra. This study will not only assist researchers in developing effective okra gum-based extended-release matrices but also expected to contribute towards its exploration at an industrial scale.

Preparation of Gelatin and Gelatin/Hyaluronic Acid Cryogel Scaffolds for the 3D Culture of Mesothelial Cells and Mesothelium Tissue Regeneration

Mesothelial cells are specific epithelial cells that are lined in the serosal cavity and internal organs. Nonetheless, few studies have explored the possibility to culture mesothelial cells in a three-dimensional (3D) scaffold for tissue engineering applications. Towards this end, we fabricated macroporous scaffolds from gelatin and gelatin/hyaluronic acid (HA) by cryogelation, and elucidated the influence of HA on cryogel properties and the cellular phenotype of mesothelial cells cultured within the 3D scaffolds. The incorporation of HA was found not to significantly change the pore size, porosity, water uptake kinetics, and swelling ratios of the cryogel scaffolds, but led to a faster scaffold degradation in the collagenase solution. Adding 5% HA in the composite cryogels also decreased the ultimate compressive stress (strain) and toughness of the scaffold, but enhanced the elastic modulus. From the in vitro cell culture, rat mesothelial cells showed quantitative cell viability in gelatin (G) and gelatin/HA (GH) cryogels. Nonetheless, mesothelial cells cultured in GH cryogels showed a change in the cell morphology and cytoskeleton arrangement, reduced cell proliferation rate, and downregulation of the mesothelium specific maker gene expression. The production of key mesothelium proteins E-cadherin and calretinin were also reduced in the GH cryogels. Choosing the best G cryogels for in vivo studies, the cell/cryogel construct was used for the transplantation of allograft mesothelial cells for mesothelium reconstruction in rats. A mesothelium layer similar to the native mesothelium tissue could be obtained 21 days post-implantation, based on hematoxylin and eosin (H&E) and immunohistochemical staining.

A pH-regulated drug delivery dermal patch for targeting infected regions in chronic wounds

This work presents a low-cost, passive, flexible, polymeric pump for topical drug delivery which uses wound pH as a trigger for localized drug release. Its operation relies on a pH-responsive hydrogel actuator which swells when exposed to the alkaline pH of an infected wound. The pump enables slow release (<0.1 μL min-1) of aqueous anti-bacterial solution for up to 4 hours and sustains against up to 8 kPa of backpressure. Featuring a scalable layer-by-layer fabrication technique to expand the pump into a 2 × 2 array, the device can dispense 50 μl onto a 160 mm2 dermal coverage within 4 hours. Robustness tests show that when integrated within a medical adhesive, the device can be worn around the forearm and can withstand various daily activities (non-intensive) for up to 12 hours. In vitro experiments demonstrate a 58 times decrease of live P. aeruginosa after 24 hours of the pump assisted antibiotics treatment.

Second harmonic generation microscopy of collagen organization in tunable, environmentally responsive alginate hydrogels

We fabricated photocrosslinked, environmentally responsive alginate hydrogels for tissue engineering applications. Methacrylated alginate (ALGMA) hydrogels were prepared across a variety and combination of ionic and covalent (chain growth, step growth, and mixed mode) crosslinking strategies to obtain a range of compressive moduli from 9.3 ± 0.2 kPa for the softest ionically crosslinked hydrogels to 22.6 ± 0.3 kPa for the dually crosslinked ionic mixed mode gels. The swelling behavior of the alginate hydrogels was significantly higher under basic pH conditions. Stiffer gels consistently swelled to a lesser degree compared to softer gels for all conditions. These hydrogels were stable - retaining >80% of their original mass for three weeks - when incubated in a basic solution of diluted sodium hydroxide, which mimicked accelerated degradation conditions. Encapsulated NIH/3T3 fibroblasts remained viable and proliferated significantly more in stiffer hydrogel substrates compared to softer gels. Additionally, the collagen secreted by encapsulated fibroblasts was quantifiably compared using second harmonic generation (SHG) imaging. Fibroblasts encapsulated in the softer hydrogels secreted significantly less collagen than the stiffer gels. The collagen in these softer gels was also more aligned than the stiffer gels. The ability to tune collagen organization using hydrogels has potential applications ranging from corneal wound healing where organized collagen is desired to epithelial wound scaffolds where a random organization is preferable.

pH-Sensitive Hydrogel from Polyethylene Oxide and Acrylic acid by Gamma Radiation

Hydrogel as a good water absorbent has attracted great research interest. A series of hydrogel based on polyethylene oxide (PEO) and acrylic acid (AAc) was prepared by applying gamma radiation with variation in the concentration of acrylic acid. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the PEO/ AAc hydrogel. The properties of the prepared hydrogels such as gel content, swelling behavior, tensile strength, and pH sensitivity were evaluated. The formation of the hydrogels was confirmed from FTIR spectra. SEM images showed the inner porous structure of the hydrogels. The dose of gamma radiation was optimized to get a hydrogel with good swelling property and mechanical strength. The swelling ratio and gel content of the hydrogels were increased with increasing acrylic acid content. The pH of the solutions affected the swelling which indicated the pH-responsive property of the prepared hydrogels. Swelling of the prepared hydrogels in sodium chloride salt solutions decreased with increasing the ionic strength.

Transport and delivery of interferon-α through epithelial tight junctions via pH-responsive poly(methacrylic acid-grafted-ethylene glycol) nanoparticles

Whereas significant advancements have been made in our fundamental understanding of cancer, they have not yet translated into effective clinical cancer treatments. One of the areas that has the potential to improve the efficacy of cancer therapies is the development of novel drug delivery technologies. In particular, the design of pH-sensitive polymeric complexation hydrogels may allow for targeted oral delivery of a wide variety of chemotherapeutic drugs and proteins. In this work, poly(methacrylic acid-grafted-ethylene glycol) hydrogel nanoparticles were synthesised, characterised, and studied as matrix-type, diffusion-controlled, pH-responsive carriers to enable the oral delivery of the chemotherapeutic agent interferon alpha (IFN-α). The biophysical mechanisms controlling the transport of IFN-α were investigated using a Caco-2/HT29-MTX co-culture as a gastrointestinal (GI) tract model. The synthesised nanoparticles exhibited pH-responsive swelling behaviour and allowed the permeation of IFN-α through the tight junctions of the developed cellular GI epithelium model. These studies demonstrate the capabilities of these particles to contribute to the improved oral delivery of protein chemotherapeutics.