Fabrication of Stimuli-Responsive Quince/Mucin Co-Poly (Methacrylate) Hydrogel Matrices for the Controlled Delivery of Acyclovir Sodium: Design, Characterization and Toxicity Evaluation

Free-radical polymerization technique was adopted to fabricate a stimuli-responsive intelligent quince/mucin co-poly (methacrylate) hydrogel for the controlled delivery of acyclovir sodium. The developed hydrogel matrices were appraised using different parameters, such as drug loading (%), swelling kinetics, pH- and electrolyte-responsive swelling, and sol-gel fraction. Drug-excipient compatibility study, scanning electron microscopy, thermal analysis, powder X-ray diffraction (PXRD) analysis, in vitro drug release studies, drug release kinetics and acute oral toxicity studies were conducted. The results of drug loading revealed an acyclovir sodium loading of 63-75% in different formulations. The hydrogel discs exhibited pH-responsive swelling behavior, showing maximum swelling in a phosphate buffer with a pH of 7.4, but negligible swelling was obvious in an acidic buffer with a pH of 1.2. The swelling kinetics of the developed hydrogel discs exhibited second-order kinetics. Moreover, the hydrogel discs responded to the concentration of electrolytes (CaCl₂ and NaCl). The results of the FTIR confirm the formation of the hydrogel via free-radical polymerization. However, the major peaks of acyclovir remain intact, proving drug-excipient compatibility. The results of the SEM analysis reveal the porous, rough surface of the hydrogel discs with multiple cracks and pores over the surface. The results of the PXRD disclose the amorphous nature of the fabricated hydrogel. The dissolution studies showed a minor amount of acyclovir sodium released in an acidic environment, while an extended release up to 36 h in the phosphate buffer was observed. The drug release followed Hixen-Crowell's kinetics with Fickian diffusion mechanism. The toxicity studies demonstrated the non-toxic nature of the polymeric carrier system. Therefore, these results signify the quince/mucin co-poly (methacrylate) hydrogel as a smart material with the potential to deliver acyclovir into the intestine for an extended period of time.

Current state of knowledge on intelligent-response biological and other macromolecular hydrogels in biomedical engineering: A review

Because intelligent hydrogels have good biocompatibility, a rapid response, and good degradability as well as a stimulus response mode that is rich, hydrophilic, and similar to the softness and elasticity of living tissue, they have received widespread attention and are widely used in biomedical engineering. In this article, we conduct a systematic review of the use of smart hydrogels in biomedical engineering. First, we introduce the properties and applications of hydrogels and compare the similarities and differences between traditional hydrogels and smart hydrogels. Secondly, we summarize the intelligent hydrogel types, the mechanisms of action used by different hydrogels, and the materials for preparing different types of hydrogels, such as the materials for the preparation of temperature-responsive hydrogels, which mainly include gelatin, carrageenan, agarose, amylose, etc.; summarize the morphologies of different hydrogels, such as films, fibers and microspheres; and summarize the application of smart hydrogels in biomedical engineering, such as for the delivery of proteins, antibiotics, deoxyribonucleic acid, etc. Finally, we summarize the shortcomings of current research and present future prospects for smart hydrogels. The purpose of this paper is to provide researchers engaged in related fields with a systematic review of the application of intelligent hydrogels in biomedical engineering. We hope that they will get some inspiration from this work to provide new directions for the development of related fields.

Stimulus responsive microcapsules and their aromatic applications

Fragrances and essential oils are promising for a wide range of applications due to their pleasant odors and diverse effects. However, direct addition to consumer products has the disadvantages of short retention time and easy deterioration of odor. At the same time, releasing a large amount of odor in a short time may be an unpleasant experience, which severely limits the practical application of aromatic substances. Microencapsulation perfectly solves these problems. Stimuli-responsive microcapsules, which combine environmental stimulation with microencapsulation, can not only effectively prevent the rapid decomposition and evaporation of aroma components, but also realize the "on-off" intelligent release of aroma substances to environmental changes, which have great promise in the field of fragrances. In this review, the application of stimuli-responsive microcapsules in fragrances is highlighted. Firstly, various encapsulation materials used to prepare stimuli-responsive aromatic microcapsules are described, mainly including some natural polymers, synthetic polymers, and inorganic materials. Subsequently, there is a detailed description of the common release mechanisms of stimuli-responsive aromatic microcapsules are described in detail. Finally, the application and future research directions are given for stimuli-responsive aromatic microcapsules in new textiles, food, paper, and leather.

Stimuli-responsive destructible polymeric hydrogels based on irreversible covalent bond dissociation

Covalently crosslinked stimuli-destructible hydrogels with the ability of irreversible bond dissociation have attracted great attentions due to their biodegradability, stability against hydrolysis, and controlled solubility upon insertion of desired triggers.

Design and Fabrication of Dual Redox Responsive Nanoparticles with Diselenide Linkage Combined Photodynamically to Effectively Enhance Gene Expression

BACKGROUND

PEI is currently the most used non-viral gene carrier and the transfection efficiency is closely related to the molecular weight; however, the prominent problem is that the cytotoxicity increased with the molecular weight.

METHODS

A novel redox responsive biodegradable diselenide cross-linked polymer (dPSP) was designed to enhance gene expression. ICG-pEGFP-TRAIL/dPSP nanoparticles with high drug loading are prepared, which have redox sensitivity and plasmid protection. The transfection efficiency of dPSP nanoparticle was evaluated in vitro.

RESULTS

The plasmid was compressed by 100% at the N/P ratio of 16, and the particle size was less than 100 nm. When explored onto high concentrations of GSH/H2O2, dPSP4 degraded into small molecular weight cationic substances with low cytotoxicity rapidly. Singlet oxygen (1O2) was produced when indocyanine green (ICG) was irradiated by near-infrared laser irradiation (NIR) to promote oxidative degradation of dPSP4 nanoparticles. Under the stimulation of NIR 808 and redox agent, the particle size and PDI of ICG-pDNA/dPSP nanoparticle increased significantly.

CONCLUSION

Compared with gene therapy alone, co-transportation of dPSP4 nanoparticle with ICG and pEGFP-TRAIL had better antitumor effect. Diselenide-crosslinked polyspermine had a promising prospect on gene delivery and preparation of multifunctional anti-tumor carrier.

Structural reorganization and crack-healing properties of hydrogels based on dynamic diselenide linkages

We report the dynamic behavior of diselenide-containing hydrophilic polyurethanes and hydrogels based on diselenide exchange reactions in an aqueous media. Diselenide-containing linear and cross-linked polyurethanes were synthesized via polyaddition reactions using diselenide-containing diol in combination with pyridinium diol that enhances the hydrophilicity of the polymer chains. The obtained linear polyurethanes underwent photo-induced diselenide exchange reactions with small diselenide compounds and degraded to smaller fragments, confirming the dynamicity of the obtained hydrophilic polyurethanes. The prepared hydrogels displayed characteristic large swelling behavior based on the structural reorganization through diselenide exchange either under photo-irradiation at 365 nm or even in the dark at room temperature. The diselenide-containing hydrogels also showed crack-healing behavior under the same exchanging conditions, presenting the utility of diselenide linkages as simple and useful units to offer high dynamicity to hydrogels.

Nanocomposite hydrogel actuators hybridized with various dimensional nanomaterials for stimuli responsiveness enhancement

Hydrogel actuators, that convert external energy, such as pH, light, heat, magnetic field, and ion strength, into mechanical motion, have been utilized in sensors, artificial muscles, and soft robotics. For a practicality of the hydrogel actuators in a wide range of fields, an establishment of robust mechanical properties and rapid response are required. Several solutions have been proposed, for example, setting porous and anisotropy structures to hydrogels with nanocomposite materials to improve the response speed and deformation efficiency. In this review paper, we focused on hydrogel actuators including various nanocomposite by categorizing the dimensional aspects of additive materials. Moreover, we described the role of diverse additive materials in terms of the improvement of mechanical property and deformation efficiency of the hydrogel actuators. We assumed that this review will provide a beneficial guidance for strategies of developing nanocomposite hydrogel actuators and outlooks for the future research directions.

A glimpse of biodegradable polymers and their biomedical applications

Over the past two decades, biodegradable polymers (BPs) have been widely used in biomedical applications such as drug carrier, gene delivery, tissue engineering, diagnosis, medical devices, and antibacterial/antifouling biomaterials. This can be attributed to numerous factors such as chemical, mechanical and physiochemical properties of BPs, their improved processibility, functionality and sensitivity towards stimuli. The present review intended to highlight main results of research on advances and improvements in terms of synthesis, physical properties, stimuli response, and/or applicability of biodegradable plastics (BPs) during last two decades, and its biomedical applications. Recent literature relevant to this study has been cited and their developing trends and challenges of BPs have also been discussed.

Programmable hydrogels

Programmable hydrogels are defined as hydrogels that are able to change their properties and functions periodically, reversibly and/or sequentially on demand. They are different from those responsive hydrogels whose changes are passive or cannot be stopped or reversed once started and vice versa. The purpose of this review is to summarize major progress in developing programmable hydrogels from the viewpoints of principles, functions and biomedical applications. The principles are first introduced in three categories including biological, chemical and physical stimulation. With the stimulation, programmable hydrogels can undergo functional changes in dimension, mechanical support, cell attachment and molecular sequestration, which are introduced in the middle of this review. The last section is focused on the introduction and discussion of four biomedical applications including mechanistic studies in mechanobiology, tissue engineering, cell separation and protein delivery.

Drug delivery systems for programmed and on-demand release

With the advancement in medical science and understanding the importance of biodistribution and pharmacokinetics of therapeutic agents, modern drug delivery research strives to utilize novel materials and fabrication technologies for the preparation of robust drug delivery systems to combat acute and chronic diseases. Compared to traditional drug carriers, which could only control the release of the agents in a monotonic manner, the new drug carriers are able to provide a precise control over the release time and the quantity of drug introduced into the patient's body. To achieve this goal, scientists have introduced "programmed" and "on-demand" approaches. The former provides delivery systems with a sophisticated architecture to precisely tune the release rate for a definite time period, while the latter includes systems directly controlled by an operator/practitioner, perhaps with a remote device triggering/affecting the implanted or injected drug carrier. Ideally, such devices can determine flexible release pattern and intensify the efficacy of a therapy via controlling time, duration, dosage, and location of drug release in a predictable, repeatable, and reliable manner. This review sheds light on the past and current techniques available for fabricating and remotely controlling drug delivery systems and addresses the application of new technologies (e.g. 3D printing) in this field.

Enhanced bioreduction-responsive biodegradable diselenide-containing poly(ester urethane) nanocarriers

Stimuli-responsive nanocarriers have been limited for bench-to-bedside translation mainly because the stimuli sensitivity and responsive rate are not high enough to ensure sufficient drug concentration at the target sites for superior therapeutic benefits. Herein, we reported an enhanced bioreduction-responsive and biodegradable nanocarrier based on the amphiphilic poly(ester urethane) copolymers (PAUR-SeSe) bearing multiple diselenide groups on the backbone. The copolymer could spontaneously self-assemble into stable micelles in aqueous medium with an average diameter of 68 nm, which could be rapidly disassembled in a reductive environment as a result of the reduction-triggered cleavage of diselenide groups. Furthermore, the PAUR-SeSe micelles showed an enhanced drug release profile and cellular uptake compared with the disulfide-containing analogue (PAUR-SS). CCK8 assays revealed that the antitumor activity of DOX-loaded PAUR-SeSe micelles was much higher than that of DOX-loaded PAUR-SS micelles. Besides, the blank micelles and degradation products were nontoxic up to a tested concentration of 50 μg mL^-1. Therefore, the enhanced therapeutic efficacy and good biocompatibility demonstrated that this drug nanocarrier had great potential for smart antitumor drug delivery applications.

Chemical Synthesis of Biomimetic Hydrogels for Tissue Engineering

Owing to the high water content, porous structure, biocompatibility and tissue-like viscoelasticity, hydrogels have become attractive and promising biomaterials for use in drug delivery, 3D cell culture and tissue engineering applications. Various chemical approaches have been developed for hydrogel synthesis using monomers or polymers carrying reactive functional groups. For in vivo tissue repair and in vitro cell culture purposes, it is desirable that the crosslinking reactions occur under mild conditions, do not interfere with biological processes and proceed at high yield with exceptional selectivity. Additionally, the cross-linking reaction should allow straightforward incorporation of bioactive motifs or signaling molecules, at the same time, providing tunability of the hydrogel microstructure, mechanical properties, and degradation rates. In this review, we discuss various chemical approaches applied to the synthesis of complex hydrogel networks, highlighting recent developments from our group. The discovery of new chemistries and novel materials fabrication methods will lead to the development of the next generation biomimetic hydrogels with complex structures and diverse functionalities. These materials will likely facilitate the construction of engineered tissue models that may bridge the gap between 2D experiments and animal studies, providing preliminary insight prior to in vivo assessments.

Stimuli-responsive chitosan-based nanocarriers for cancer therapy

Introduction: Stimuli-responsive nanocarriers offer unique advantages over the traditional drug delivery systems (DDSs) in terms of targeted drug delivery and on-demand release of cargo drug molecules. Of these, chitosan (CS)-based DDSs offer several advantages such as high compatibility with biological settings. Methods: In this study, we surveyed the literature in terms of the stimuli-responsive nanocarriers and discussed the most recent advancements in terms of CS-based nanosystems and their applications in cancer therapy and diagnosis. Results: These advanced DDSs are able to release the entrapped drugs in response to a specific endogenous stimulus (e.g., pH, glutathione concentration or certain enzymes) or exogenous stimulus (e.g., temperature, light, ultrasound, and magnetic field) at the desired time and target site. Dual-responsive nanocarriers by the combination of different stimuli have also been developed as efficient and improved DDSs. Among the stimuli-responsive nanocarriers, CS-based DDSs offer several advantages, including biocompatibility and biodegradability, antibacterial activity, ease of modification and functionalization, and non-immunogenicity. They are as one of the most ideal smart multifunction DDSs. Conclusion: The CS-based stimuli-responsive multifunctional nanosystems (NSs) offer unique potential for the targeted delivery of anticancer agents and provide great potential for on-demand and controlled-release of anticancer agents in response to diverse external/internal stimuli.

Intelligent Textiles with Comfort Regulation and Inhibition of Bacterial Adhesion Realized by Cross-Linking Poly(n-isopropylacrylamide-co-ethylene glycol methacrylate) to Cotton Fabrics

Comfort regulation and inhibition of bacterial adhesion to textiles is realized by cross-linking thermoresponsive random copolymer to the cotton fabrics. By introduction of ethylene glycol methacrylate (EGMA) monomers into n-isopropylacrylamide (NIPAM) with a molar ratio of 2:18, the obtained random copolymer poly(n-isopropylacrylamide-co-ethylene glycol methacrylate), abbreviated as P(NIPAM-co-EGMA), presents a transition temperature (TT) of 40 °C in an aqueous solution with a concentration of 1 mg/mL. Because of the additional EGMA in the copolymer, the obtained P(NIPAM-co-EGMA) shows a glass transition temperature (T_g) of 0 °C, which is much lower than that of pure PNIPAM (T_g = 140 °C). Therefore, the introduction of P(NIPAM-co-EGMA) into the cotton fabrics will have little influence on the softness of the fabrics. Due to the cross-linked P(NIPAM-co-EGMA) layer on the cotton fabrics, the porosity of the polymer layer can be adjusted by varying the external temperature below or above TT, showing that regulation of the air and moisture permeability as well as the body comfort are feasible in the cotton fabrics cross-linked with P(NIPAM-co-EGMA). In addition, the cross-linked P(NIPAM-co-EGMA) layer is capable of absorbing moisture in the ambient atmosphere to form a hydrated layer on top, which can inhibit bacterial adhesion to the textiles.

A degradable cross-linked polymer containing dynamic covalent selenide bond

A new method for preparing a degradable cross-linked polymer containing dynamic selenide was demonstrated.

From seleno-mediated radical polymerization to seleno-containing branched polymers and dynamic hydrogel

A protocol of introducing redox responsive Se–Se bond into well-defined hydrogel backbone.

Temperature-Responsive Smart Nanocarriers for Delivery Of Therapeutic Agents: Applications and Recent Advances

Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external stimulus when heat is applied from the outside, or can be internal when pathological lesions have a naturally elevated termperature. A low critical solution temperature (LCST) is a special feature of some polymeric materials, and most of the temperature-responsive nanocarriers have been designed based on this feature. In this review, we attempt to summarize recent efforts to prepare innovative temperature-responsive nanocarriers and discuss their novel applications.

Oxidation and temperature dual responsive polymers based on phenylboronic acid and N-isopropylacrylamide motifs

Oxidation and temperature dual responsive copolymers using ROS as a target for drug delivery have been demonstrated.

Facile and large scale in situ synthesis of the thermal responsive fluorescent SiNPs/PNIPAM hydrogels

A new type of F-SiNPs/poly(N-isopropylacrylamide) (F-SiNPs/PNIPAM) hydrogel was prepared byin situpolymerization. The composite hydrogels display visible thermal-sensitive phase transition properties.

Novel thermo-responsive hydrogel microspheres with calixcrown host molecules as cross-links for highly specific binding and controllable release of cesium

Novel thermo-responsive hydrogel microspheres containing calixcrown molecules as covalent cross-links for highly-specific binding and thermo-triggered release of cesium in seawater.