Drug release behaviors of a pH sensitive semi-interpenetrating polymer network hydrogel composed of poly(vinyl alcohol) and star poly[2-(dimethylamino)ethyl methacrylate]

Trends in sustainable chitosan-based hydrogel technology for circular biomedical engineering: A review

Eco-friendly materials have emerged in biomedical engineering, driving major advances in chitosan-based hydrogels. These hydrogels offer a promising green alternative to conventional polymers due to their non-toxicity, biodegradability, biocompatibility, environmental friendliness, affordability, and easy accessibility. Known for their remarkable properties such as drug encapsulation, delivery capabilities, biosensing, functional scaffolding, and antimicrobial behavior, chitosan hydrogels are at the forefront of biomedical research. This paper explores the fabrication and modification methods of chitosan hydrogels for diverse applications, highlighting their role in advancing climate-neutral healthcare technologies. It reviews significant scientific advancements and trends chitosan hydrogels focusing on cancer diagnosis, drug delivery, and wound care. Additionally, it addresses current challenges and green synthesis practices that support a circular economy, enhancing biomedical sustainability. By providing an in-depth analysis of the latest evidence on climate-neutral management, this review aims to facilitate informed decision-making and foster the development of sustainable strategies leveraging chitosan hydrogel technology. The insights from this comprehensive examination are pivotal for steering future research and applications in sustainable biomedical solutions.

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

A pH-Responsive Asymmetric Microfluidic/Chitosan Device for Drug Release in Infective Bone Defect Treatment

Bacterial infection is currently considered to be one of the major reasons that leads to the failure of guided bone regeneration (GBR) therapy. Under the normal condition, the pH is neutral, while the microenvironment will become acid at the sites of infection. Here, we present an asymmetric microfluidic/chitosan device that can achieve pH-responsive drug release to treat bacterial infection and promote osteoblast proliferation at the same time. On-demand release of minocycline relies on a pH-sensitive hydrogel actuator, which swells significantly when exposed to the acid pH of an infected region. The PDMAEMA hydrogel had pronounced pH-sensitive properties, and a large volume transition occurred at pH 5 and 6. Over 12 h, the device enabled minocycline solution flowrates of 0.51-1.63 µg/h and 0.44-1.13 µg/h at pH 5 and 6, respectively. The asymmetric microfluidic/chitosan device exhibited excellent capabilities for inhibiting Staphylococcus aureus and Streptococcus mutans growth within 24 h. It had no negative effect on proliferation and morphology of L929 fibroblasts and MC3T3-E1 osteoblasts, which indicates good cytocompatibility. Therefore, such a pH-responsive drug release asymmetric microfluidic/chitosan device could be a promising therapeutic approach in the treatment of infective bone defects.

Quarternized chitosan/quercetin/polyacrylamide semi-interpenetrating network hydrogel with recoverability, toughness and antibacterial properties for wound healing

Antibiotic abuse has posed enormous burdens on patients and healthcare systems. Hence, the design and development of non-antibiotic wound dressings to meet clinical demand are urgently desired. However, there remains one of the impediments to hydrogel wound dressings that integrated with good recoverability, toughness, and excellent antibacterial properties. Herein, a series of semi-interpenetrating network (semi-IPN) hydrogels with exceptional mechanical performance and remarkable antibacterial activity based on quaternized chitosan (QCS) and polyacrylamide (PAM) were developed using a one-pot method. Additionally, the antibacterial activity of semi-IPN hydrogel against S. aureus and E. coli was enhanced by integrating it with quercetin (QT). The semi-IPN hydrogels also exhibited high recoverability and toughness, outstanding liquid absorbability (the swelling ratio reached 565 ± 12 %), and a satisfying water vapor transmission rate. Moreover, the semi-IPN hydrogels presented ideal hemocompatibility and cytocompatibility. These high-elastic hydrogels are promising candidates for potential applications in wound dressing, tissue repair, chronic wound care, as well as other biomedical fields.

4D Printing of Hydrogels: Innovation in Material Design and Emerging Smart Systems for Drug Delivery

Advancements in the material design of smart hydrogels have transformed the way therapeutic agents are encapsulated and released in biological environments. On the other hand, the expeditious development of 3D printing technologies has revolutionized the fabrication of hydrogel systems for biomedical applications. By combining these two aspects, 4D printing (i.e., 3D printing of smart hydrogels) has emerged as a new promising platform for the development of novel controlled drug delivery systems that can adapt and mimic natural physio-mechanical changes over time. This allows printed objects to transform from static to dynamic in response to various physiological and chemical interactions, meeting the needs of the healthcare industry. In this review, we provide an overview of innovation in material design for smart hydrogel systems, current technical approaches toward 4D printing, and emerging 4D printed novel structures for drug delivery applications. Finally, we discuss the existing challenges in 4D printing hydrogels for drug delivery and their prospects.

Drug Delivery Platforms Containing Thermoresponsive Polymers and Mucoadhesive Cellulose Derivatives: A Review of Patents

Nowadays, the development of mucoadhesive systems for drug delivery has gained keen interest, with enormous potential in applications through different routes. Mucoadhesion characterizes an attractive interaction between the pharmaceutical dosage form and the mucosal surface. Many polymers have shown the ability to interact with mucus, increasing the residence time of local and/or systemic administered preparations, such as tablets, patches, semi-solids, and micro and nanoparticles. Cellulose is the most abundant polymer on the earth. It is widely used in the pharmaceutical industry as an inert pharmaceutical ingredient, mainly in its covalently modified forms: methylcellulose, ethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, and carboxymethylcellulose salts. Aiming to overcome the drawbacks of oral, ocular, nasal, vaginal, and rectal routes and thereby maintaining patient compliance, innovative polymer blends have gained the interest of the pharmaceutical industry. Combining mucoadhesive and thermoresponsive polymers allows for simultaneous in situ gelation and mucoadhesion, thus enhancing the retention of the system at the site of administration and drug availability. Thermoresponsive polymers have the ability to change physicochemical properties triggered by temperature, which is particularly interesting considering the physiological temperature. The present review provides an analysis of the main characteristics and applications of cellulose derivatives as mucoadhesive polymers and their use in blends together with thermoresponsive polymers, aiming at platforms for drug delivery. Patents were reviewed, categorized, and discussed, focusing on the applications and pharmaceutical dosage forms using this innovative strategy. This review manuscript also provides a detailed introduction to the topic and a perspective on further developments.

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

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

Tough Interfacial Adhesion of Bilayer Hydrogels with Integrated Shape Memory and Elastic Properties for Controlled Shape Deformation

The weak adhesion between two hydrogel layers may lead to the delamination of bilayer hydrogels or low force transfer efficiency during deformation. Here, tough interfacial adhesive bilayer hydrogels with rapid shape deformation and recovery were prepared by simple attachment-heating of two gel layers. The bilayer hydrogels, composed of a shape memory gel (S-gel) and an elastic gel (E-gel), exhibited extremely tough interfacial adhesion between two layers (Γ ∼ 2200 J/m²). The shape deformation and shape recovery of the bilayer hydrogels, tuned by "heating-stretching" mode and "stretching-heating-stretching" mode, were rapid (<5 s) and no delamination between two gel layers was detected during shape deformation. Based on the fast shape deformation and recovery, the bilayer hydrogels could mimic the flower and hand, and a gel gripper could be fabricated to catch the object in the hot water. This work provides a simple method to prepare tough adhesive bilayer hydrogels with controlled shape deformation.

Design and fabrication of dual responsive lignin-based nanogel via "grafting from" atom transfer radical polymerization for curcumin loading and release

The story of human dreams about curing all diseases, disorders and lesions is as old as human history. In the frontier of medical science, nanomedicine is trying to solve the problem. In this study, inspired by nanotechnology and using "grafting from" approach, a novel lignin-based nanogel was synthesized using atom transfer radical polymerization (ATRP) method. N-isopropylacrylamide (NIPAM) and N,N-dimethylaminoethylmethacrylate (DMAEMA) comonomers were graft copolymerized from fully brominated lignin as ATRP macroinitiator to synthesize lignin-g-P(NIPAM-co-DMAEMA) nanogel (LNDNG). By controlling the initial comonomer compositions and ATRP conditions, four LNDNG systems with different lower critical solution temperatures (LCSTs) of 32, 34, 37 and 42 °C were prepared. The LNDNGs were evaluated by GPC, FT-IR, 1H NMR, UV-Vis, DLS, SEM and TEM analyses. The prepared nanogels exhibited an average diameter of 150 nm with dual temperature and pH responsiveness. Curcumin (CUR) loading capacity and encapsulation efficiency of the LNDNGs were 49.69% and 92.62% on average, respectively. The cumulative release amount of loaded CUR was observed to be 65.36% after 72 h. The new lignin-based NGs proposed in the present work seems to be a promising, safe and comparable system in a near future.

Interaction between mucoadhesive cellulose derivatives and Pluronic F127: Investigation on the micelle structure and mucoadhesive performance

Systems composed of bioadhesive and thermoresponsive polymers can combine in situ gelation with bio/mucoadhesion, enhancing retention of topically applied drugs. The effect of bioadhesive sodium carboxymethylcellulose (NaCMC) and hydroxypropyl methylcellulose cellulose (HPMC) on the properties of thermoresponsive Pluronic® F127 (F127) was explored, including micellization and the mucoadhesion. A computational analysis between these polymers and their molecular interactions were also studied, rationalising the design of improved binary polymeric systems for pharmaceutical and biomedical applications. The morphological characterization of polymeric systems was conducted by SEM. DSC analysis was used to investigate the crystallization and micellization enthalpy of F127 and the mixed systems. Micelle size measurements and TEM micrographs allowed for investigation into the interference of cellulose derivatives on F127 micellization. Both cellulose derivatives reduced the critical micellar concentration and enthalpy of micellization of F127, altering hydrodynamic diameters of the aggregates. Mucoadhesion performance was useful to select the best systems for mucosal application. The systems composed of 17.5% (w/w) F127 and 3% (w/w) HPMC or 1% (w/w) NaCMC are promising as topical drug delivery systems, mainly on mucosal surfaces. They were biocompatible when tested against Artemia salina, and also able to release a model of hydrophilic drug in a controlled manner.

Stimuli-Responsive Polymeric Nanocarriers for Drug Delivery, Imaging, and Theragnosis

In the past few decades, polymeric nanocarriers have been recognized as promising tools and have gained attention from researchers for their potential to efficiently deliver bioactive compounds, including drugs, proteins, genes, nucleic acids, etc., in pharmaceutical and biomedical applications. Remarkably, these polymeric nanocarriers could be further modified as stimuli-responsive systems based on the mechanism of triggered release, i.e., response to a specific stimulus, either endogenous (pH, enzymes, temperature, redox values, hypoxia, glucose levels) or exogenous (light, magnetism, ultrasound, electrical pulses) for the effective biodistribution and controlled release of drugs or genes at specific sites. Various nanoparticles (NPs) have been functionalized and used as templates for imaging systems in the form of metallic NPs, dendrimers, polymeric NPs, quantum dots, and liposomes. The use of polymeric nanocarriers for imaging and to deliver active compounds has attracted considerable interest in various cancer therapy fields. So-called smart nanopolymer systems are built to respond to certain stimuli such as temperature, pH, light intensity and wavelength, and electrical, magnetic and ultrasonic fields. Many imaging techniques have been explored including optical imaging, magnetic resonance imaging (MRI), nuclear imaging, ultrasound, photoacoustic imaging (PAI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). This review reports on the most recent developments in imaging methods by analyzing examples of smart nanopolymers that can be imaged using one or more imaging techniques. Unique features, including nontoxicity, water solubility, biocompatibility, and the presence of multiple functional groups, designate polymeric nanocues as attractive nanomedicine candidates. In this context, we summarize various classes of multifunctional, polymeric, nano-sized formulations such as liposomes, micelles, nanogels, and dendrimers.

Thermoresponsive systems composed of poloxamer 407 and HPMC or NaCMC: mechanical, rheological and sol-gel transition analysis

Poloxamer 407 (polox407) is widely studied as thermogelling polymer, transitioning to a gel state when warmed Polox407 forms weak hydrogels with rapid dissolution in excess solvent. This study reports the development of binary systems composed of polox407 and hydroxypropyl methylcellulose (HPMC) or sodium carboxymethylcellulose (NaCMC) aiming to improve the rheological and mechanical properties of the hydrogel. The interaction between polox407 and cellulose derivatives was studied, and their interaction with biological surfaces predicted. The carbohydrates affected the mechanical and rheological behavior of polox407 in different ways, dependent on polymer type, concentration, and temperature. T_sol/gel and rheological interaction parameters were useful to select the most suitable formulations for topical or local application. Most of the binary systems exhibited plastic behavior, thixotropy and viscoelastic properties. Appropriate formulations were identified for local application, such as 17.5/3; 17.5/4; 20/3 and 20/4 (%, w/w) for polox407/HPMC; and 17.5/1; 17.5/1.5; 20/1 and 20/1.5 (%, w/w) for polox407/NaCMC.

Double stimuli-responsive cellulose nanocrystals reinforced electrospun PHBV composites membrane for intelligent drug release

Double stimuli-responsive functionalized cellulose nanocrystal-poly[2-(dimethylamino)ethyl methacrylate] (CNC-g-PDMAEMA) reinforced poly(3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) electrospun composite membranes were explored as drug delivery vehicles using tetracycline hydrochloride (TH) as a model drug. It was found that rigid CNC-g-PDMAEMA nanoparticles enhanced thermal, crystallization and hydrophilic properties of PHBV. Moreover, great improvements in fiber diameter uniformity, crystallization ability and maximum decomposition temperature (T_max) could be achieved at 6 wt% CNC-g-PDMAEMA. Furthermore, by introducing stimuli-responsive CNC-g-PDMAEMA nanofillers, intelligent and long-term sustained release behavior of composite membranes could be achieved. The releasing mechanism of composite membranes based on zero order, first order, Higuchi and Korsmeyere-Peppas mathematical models was clearly demonstrated, giving effective technical guidance for practical drug delivery systems.

Thermosensitive Hydrogel for Encapsulation and Controlled Release of Biocontrol Agents to Prevent Peanut Aflatoxin Contamination

Starch, alginate, and poly(N-isopropylacrylamide) (PNIPAAm) were combined to prepare a semi-interpenetrating network (IPN) hydrogel with temperature sensitivity. Calcium chloride was used as cross-linking agent, the non-toxigenic Aspergillus flavus spores were successfully encapsulated as biocontrol agents by the method of ionic gelation. Characterization of the hydrogel was performed by Fourier-transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), and thermogravimetry analysis (TGA). Formulation characteristics, such as entrapment efficiency, beads size, swelling behavior, and rheological properties were evaluated. The optical and rheological measurements indicated that the lower critical solution temperature (LCST) of the samples was about 29-30 °C. TGA results demonstrated that the addition of kaolin could improve the thermal stability of the semi-IPN hydrogel. Morphological analysis showed a porous honeycomb structure on the surface of the beads. According to the release properties of the beads, the semi-IPN hydrogel beads containing kaolin not only have the effect of slow release before peanut flowering, but they also can rapidly release biocontrol agents after flowering begins. The early flowering stage of the peanut is the critical moment to apply biocontrol agents. Temperature-sensitive hydrogel beads containing kaolin could be considered as carriers of biocontrol agents for the control of aflatoxin in peanuts.

Review of Stimuli-Responsive Polymers in Drug Delivery and Textile Application

This review describes some commercially available stimuli-responsive polymers of natural and synthetic origin, and their applications in drug delivery and textiles. The polymers of natural origin such as chitosan, cellulose, albumin, and gelatin are found to show both thermo-responsive and pH-responsive properties and these features of the biopolymers impart sensitivity to act differently under different temperatures and pH conditions. The stimuli-responsive characters of these natural polymers have been discussed in the review, and their respective applications in drug delivery and textile especially for textile-based transdermal therapy have been emphasized. Some practically important thermo-responsive polymers such as pluronic F127 (PF127) and poly(N-isopropylacrylamide) (pNIPAAm) of synthetic origin have been discussed in the review and they are of great importance commercially because of their in situ gel formation capacity. Some pH-responsive synthetic polymers have been discussed depending on their surface charge, and their drug delivery and textile applications have been discussed in this review. The selected stimuli-responsive polymers of synthetic origin are commercially available. Above all, the applications of bio-based or synthetic stimuli-responsive polymers in textile-based transdermal therapy are given special regard apart from their general drug delivery applications. A special insight has been given for stimuli-responsive hydrogel drug delivery systems for textile-based transdermal therapy, which is critical for the treatment of skin disease atopic dermatitis.

Electrophoretic fabrication of an active and selective wrinkle surface on hydrogels

We developed a novel method for the fabrication of a wrinkle structure on the hydrogel surface in aqueous conditions by the electrophoretic formation of a polyion complex.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

Development of Gallic Acid-Modified Hydrogels Using Interpenetrating Chitosan Network and Evaluation of Their Antioxidant Activity

In this work, antioxidant hydrogels were prepared by the construction of an interpenetrating chitosan network and functionalization with gallic acid. The poly(2-hydroxyethyl methacrylate) p(HEMA)-based hydrogels were first synthesized and subsequently surface-modified with an interpenetrating polymer network (IPN) structure prepared with methacrylamide chitosan via free radical polymerization. The resulting chitosan-IPN hydrogels were surface-functionalized with gallic acid through an amide coupling reaction, which afforded the antioxidant hydrogels. Notably, gallic-acid-modified hydrogels based on a longer chitosan backbone exhibited superior antioxidant activity than their counterpart with a shorter chitosan moiety; this correlated to the amount of gallic acid attached to the chitosan backbone. Moreover, the surface contact angles of the chitosan-modified hydrogels decreased, indicating that surface functionalization of the hydrogels with chitosan-IPN increased the wettability because of the presence of the hydrophilic chitosan network chain. Our study indicates that chitosan-IPN hydrogels may facilitate the development of applications in biomedical devices and ophthalmic materials.

Effect of in situ modification of bacterial cellulose with carboxymethylcellulose on its nano/microstructure and methotrexate release properties

Bacterial cellulose/carboxymethylcelullose (BC/CMC) biocomposites with different DS-CMC (DS from 0.7 to 1.2) were developed in order to evaluate their impact as a drug delivery system. Biocomposites were loaded with methotrexate (MTX) as an alternative for the topical treatment of psoriasis. Scanning electron microscopy and atomic force microscopy showed that the CMC coated the cellulose nanofibers, leading to the decrease of the elastic modulus as the DS of CMC increased. BC/CMC0.9 exhibited the lower liquid uptake (up to 11 times lower), suggesting that the more linear structure of the intermediate substitute CMC grade (0.9) was able to interact more strongly with BC, resulting in a denser structure. All samples showed a typical burst release effect in the first 15min of test, however the BC/CMC0.9 biocomposite promoted a slight lowering of MTX release rates, suggesting that the DS of CMC can be considered the key factor to modulate the BC properties.

Nano-Star-Shaped Polymers for Drug Delivery Applications

With the advancement of polymer engineering, complex star-shaped polymer architectures can be synthesized with ease, bringing about a host of unique properties and applications. The polymer arms can be functionalized with different chemical groups to fine-tune the response behavior or be endowed with targeting ligands or stimuli responsive moieties to control its physicochemical behavior and self-organization in solution. Rheological properties of these solutions can be modulated, which also facilitates the control of the diffusion of the drug from these star-based nanocarriers. However, these star-shaped polymers designed for drug delivery are still in a very early stage of development. Due to the sheer diversity of macromolecules that can take on the star architectures and the various combinations of functional groups that can be cross-linked together, there remain many structure-property relationships which have yet to be fully established. This review aims to provide an introductory perspective on the basic synthetic methods of star-shaped polymers, the properties which can be controlled by the unique architecture, and also recent advances in drug delivery applications related to these star candidates.

Multi-responsive hydrogels with UCST- and LCST-induced shrinking and controlled release behaviors of rhodamine B

By using a disulfide-functionalized crosslinker, a pH- and thermo-responsive 2-(dimethylamino) ethyl methacrylate (DMAEMA) monomer and a zwitterionic sulfobetaine methacrylate (SBMA) monomer were conjugated to fabricate a multi-responsive P(DMAEMA-SS-SBMA) copolymeric hydrogel. Apparent UCST and LCST volume transitions were observed in the P(DMAEMA-SS-SBMA) hydrogels with equivalent weight fractions of monomers. Different pore size and response sensitivity of shrunken structures below UCST and above LCST were visualized by SEM images. The hydrogel exhibited a highly swollen state with a swelling ratio of 17.8 and a pore size of 106μm at 45°C, they deswelled unequally at 5°C with a compact surface with pore size of 30μm and a loose bulk with pore size of 83μm, while they deswelled uniformly at 65°C with dense shrunken structure with small pore size of 12μm. The dual-thermoresponsive hydrogel was promising in controlled drug release. The initial drug release was predominantly controlled by diffusion, and the long-term release was influenced by the swelling ratio. Below UCST, the relatively hydrophilic shrunken structure and slow diffusion had a synergistic effect on the sustained release. Above LCST, the fast diffusion and the rapid "off" effect of hydrophobic skin layer resulted in a burst release. Additionally, pH-tunable swelling and redox-sensitive degradation were also observed.

Thermoresponsive hydrogels based on a phosphorylated star-shaped copolymer: mimicking the extracellular matrix for in situ bone repair

A bioinspired hydrogel prepared using a star-polymer exhibits sol to gel transition to induce in situ biomineralization and facilitate cell proliferation.

Diverse gatekeepers for mesoporous silica nanoparticle based drug delivery systems

Progress on the design of diverse gatekeepers for mesoporous silica nanoparticle based drug delivery systems is summarized.

Semi-Interpenetrating Polymer Networks with Predefined Architecture for Metal Ion Fluorescence Monitoring

The development of new synthetic approaches for the preparation of efficient 3D luminescent chemosensors for transition metal ions receives considerable attention nowadays, owing to the key role of the latter as elements in biological systems and their harmful environmental effects when present in aquatic media. In this work, we describe an easy and versatile synthetic methodology that leads to the generation of nonconjugated 3D luminescent semi-interpenetrating amphiphilic networks (semi-IPN) with structure-defined characteristics. More precisely, the synthesis involves the encapsulation of well-defined poly(9-anthrylmethyl methacrylate) (pAnMMA) (hydrophobic, luminescent) linear polymer chains within a covalent poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) hydrophilic polymer network, derived via the 1,2-bis-(2-iodoethoxy)ethane (BIEE)-induced crosslinking process of well-defined pDMAEMA linear chains. Characterization of their fluorescence properties demonstrated that these materials act as strong blue emitters when exposed to UV irradiation. This, combined with the presence of the metal-binding tertiary amino functionalities of the pDMAEMA segments, allowed for their applicability as sorbents and fluorescence chemosensors for transition metal ions (Fe3+, Cu2+) in solution via a chelation-enhanced fluorescence-quenching effect promoted within the semi-IPN network architecture. Ethylenediaminetetraacetic acid (EDTA)-induced metal ion desorption and thus material recyclability has been also demonstrated.

Co-delivery of drugs and plasmid DNA for cancer therapy

Cancer is an extremely complex disease involving multiple signaling pathways that enable tumor cells to evade programmed cell death, thus making cancer treatment extremely challenging. The use of combination therapy involving both gene therapy and chemotherapy has resulted in enhanced anti-cancer effects and has become an increasingly important strategy in medicine. This review will cover important design parameters that are incorporated into delivery systems for the co-administration of drug and plasmid-based nucleic acids (pDNA and shRNA), with particular emphasis on polymers as delivery materials. The unique challenges faced by co-delivery systems and the strategies to overcome such barriers will be discussed. In addition, the advantages and disadvantages of combination therapy using separate carrier systems versus the use of a single carrier will be evaluated. Finally, future perspectives in the design of novel platforms for the combined delivery of drugs and genes will be presented.

Extraction Method Plays Critical Role in Antibacterial Activity of Propolis-Loaded Hydrogels

Extracted propolis has been used for a long time as a remedy. However, if the release rate of propolis is not controlled, the efficacy is reduced. To overcome this issue, extracted propolis was added to a cryogel system. Propolis collected from southern Brazil was extracted using different methods and loaded at different concentrations into polyvinyl alcohol (PVA) and polyacrylic acid hydrogels as carrier systems. The material properties were investigated with a focus on the propolis release profiles and the cryogel antibacterial properties against 4 different bacteria, namely: Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Pseudomonas putida. Swelling studies indicated that the swelling of the hydrogel was inversely related to propolis content. In addition, propolis release studies indicated a decreased release rate with increased propolis loading. PVA and PVA/polyacrylic acid-loaded propolis were effective against all 4 bacteria studied. These results indicate that the efficacy of propolis can be enhanced by incorporation into hydrogel carrier systems and that hydrogels with higher concentrations of propolis can be considered for use as bactericide dressing.

Mechanisms and biomaterials in pH-responsive tumour targeted drug delivery: A review

As the mainstay in the treatment of various cancers, chemotherapy plays a vital role, but still faces many challenges, such as poor tumour selectivity and multidrug resistance (MDR). Targeted drug delivery using nanotechnology has provided a new strategy for addressing the limitations of the conventional chemotherapy. In the last decade, the volume of research published in this area has increased tremendously, especially with functional nano drug delivery systems (nanocarriers). Coupling a specific stimuli-triggered drug release mechanism with these delivery systems is one of the most prevalent approaches for improving therapeutic outcomes. Among the various stimuli, pH triggered delivery is regarded as the most general strategy, targeting the acidic extracellular microenvironment and intracellular organelles of solid tumours. In this review, we discuss recent advances in the development of pH-sensitive nanocarriers for tumour-targeted drug delivery. The review focuses on the chemical design of pH-sensitive biomaterials, which are used to fabricate nanocarriers for extracellular and/or intracellular tumour site-specific drug release. The pH-responsive biomaterials bring forth conformational changes in these nanocarriers through various mechanisms such as protonation, charge reversal or cleavage of a chemical bond, facilitating tumour specific cell uptake or drug release. A greater understanding of these mechanisms will help to design more efficient drug delivery systems to address the challenges encountered in conventional chemotherapy.

Dual pH-responsive micelles with both charge-conversional property and hydrophobic–hydrophilic transition for effective cellular uptake and intracellular drug release

Two types of diblock copolymers are synthesized to construct dual pH-responsive micelles with a charge-conversional property for effective drug delivery.

Investigation on polyvinyl-alcohol-based rapidly gelling hydrogels for containment of hazardous chemicals

PVA-based rapidly gelling hydrogels were prepared in situ for the containment of hazardous chemicals.

Structurally-defined semi-interpenetrating amphiphilic polymer networks with tunable and predictable mechanical response

Structurally-defined, 1,2-bis-(2-iodoethoxy)ethane (BIEE)-crosslinked semi-interpenetrating amphiphilic polymer networks were synthesized, exhibiting tunable and predictable mechanical response based on mathematical modeling.

Fabrication and Characterization of a Novel Anticancer Drug Delivery System: Salecan/Poly(methacrylic acid) Semi-interpenetrating Polymer Network Hydrogel

Salecan is a novel linear extracellular polysaccharide with a linear backbone of 1-3-linked glucopyranosyl units. Salecan is suitable for preparing hydrogels for biomedical applications due to its prominent physicochemical and biological profiles. In this contribution, a variety of innovative semi-interpenetrating polymer network (semi-IPN) hydrogels consisting of Salecan and poly(methacrylic acid) (PMAA) were developed via free radical polymerization for controlled drug delivery. The successful fabrication of the semi-IPNs was verified by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric (TGA) measurements. Scanning electron microscopy (SEM) and rheology analyses demonstrated that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the contents of Salecan and cross-linker N,N'-methylenebis(acrylamide) (BIS). Moreover, the swelling properties of these hydrogels were systematically investigated, and the results indicated that they exhibited pH sensitivity. The drug delivery applications of such fabricated hydrogels were further evaluated from which doxorubicin (Dox) was chosen as a model drug for in vitro release and cell viability studies. It was found that the Dox release from the Dox-loaded hydrogels was significantly accelerated when the pH of the release media decreased from 7.4 to 5.0. Toxicity assays confirmed that the blank hydrogels had negligible toxicity to normal cells, whereas the Dox-loaded hydrogels remained high in cytotoxicity for A549 and HepG2 cancer cells. All of these attributes implied that the new proposed semi-IPNs serve as potential drug delivery platforms for cancer therapy.

Drug Carrier for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S₀) to an excited singlet state (S₁-Sn), followed by intersystem crossing to an excited triplet state (T₁). The energy transferred from T₁ to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (¹O₂, H₂O₂, O₂*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.