Thermosensitive Biodegradable Hydrogels for Local and Controlled Cerebral Delivery of Proteins: MRI-Based Monitoring of In Vitro and In Vivo Protein Release

Current research and future potential of thermogels for sustained drug delivery

INTRODUCTION

Drug administration is ubiquitous in the healthcare field, and it is crucial to optimize drug delivery methods to improve drug efficacy, reduce systemic toxicity, and enhance patient compliance Thermogels have shown immense potential in drug delivery due to their injectability, biocompatibility, and ability to provide localized and sustained drug release.

AREA COVERED

This paper discusses the unique properties of thermogel in relation to drug kinetics and their suitability as a carrier. Different considerations and applications of thermogel drug delivery systems (DDS) were highlighted and their challenges to enter the market discussed. A comprehensive literature search was conducted using major databases such as PubMed, Scopus, and Web of Science. The search employed relevant keywords to identify studies on thermogel DDS. Clinicaltrials.gov was also utilized to determine the current state of clinical studies.

EXPERT OPINION

Nonetheless, thermogel holds great promise for the future in DDS with research achieving greater heights in terms of complexity and clinical pursuits. Their flexibility in fabrication and modularity manner makes it a great material to tailor to different drug delivery applications and to be integrated into various biomedical disciplinaries.

A Simple Method to Determine Diffusion Coefficients in Soft Hydrogels for Drug Delivery and Biomedical Applications

Biomedical applications of hydrogels are rapidly increasing due to their special properties including high water absorption capacity, viscoelasticity, swelling capability, and responsiveness to environmental physical or chemical stimuli. Two major biomedical applications of hydrogels include drug delivery and tissue engineering. Knowledge of the diffusion or degree of penetration of particles in hydrogels is key to designing specific functions such as controlled release in drug delivery systems and nutrient accessibility in tissue engineering platforms. Experimental determination of solute penetration and diffusivity can be challenging depending on several factors such as the hydrogelation process, the hydrogel characteristics, and the type of diffusing particle. We describe here a simple method that uses fluorescence intensity measurements obtained with a microplate reader to determine the concentration of diffusing particles at different penetration distances in soft hydrogels. We have analyzed the diffusion behavior of three fluorescent particles of different chemical natures and various molecular weights (fluorescein and the proteins mNeonGreen and fluorophore-labeled bovine serum albumin) in agarose hydrogels of low percentages (0.05-0.2%). The diffusion coefficients were obtained by fitting the experimental data to a one-dimensional diffusion model. A good agreement between our results and previously reported diffusion coefficients of the studied particles validates our method. We demonstrate the method's capability to adapt to hydrogels of different stiffnesses and solutes of various sizes and characteristics. In addition, the combination of hydrogel sectioning with multiple simultaneous measurements in a microplate reader shows the simplicity of the experimental procedure. Finally, our data indicate the method's sensitivity to variations in diffusion conditions, which is highly relevant to studying interactions between solutes and hydrogels designed for controlled release by determining differences in penetration distances.

Hydrogels and Nanogels: Pioneering the Future of Advanced Drug Delivery Systems

Conventional drug delivery approaches, including tablets and capsules, often suffer from reduced therapeutic effectiveness, largely attributed to inadequate bioavailability and difficulties in ensuring patient adherence. These challenges have driven the development of advanced drug delivery systems (DDS), with hydrogels and especially nanogels emerging as promising materials to overcome these limitations. Hydrogels, with their biocompatibility, high water content, and stimuli-responsive properties, provide controlled and targeted drug release. This review explores the evolution, properties, and classifications of hydrogels versus nanogels and their applications in drug delivery, detailing synthesis methods, including chemical crosslinking, physical self-assembly, and advanced techniques such as microfluidics and 3D printing. It also examines drug-loading mechanisms (e.g., physical encapsulation and electrostatic interactions) and release strategies (e.g., diffusion, stimuli-responsive, and enzyme-triggered). These gels demonstrate significant advantages in addressing the limitations of traditional DDS, offering improved drug stability, sustained release, and high specificity. Their adaptability extends to various routes of administration, including topical, oral, and injectable forms, while emerging nanogels further enhance therapeutic targeting through nanoscale precision and stimuli responsiveness. Although hydrogels and nanogels have transformative potential in personalized medicine, challenges remain in scalable manufacturing, regulatory approval, and targeted delivery. Future strategies include integrating biosensors for real-time monitoring, developing dual-stimuli-responsive systems, and optimizing surface functionalization for specificity. These advancements aim to establish hydrogels and nanogels as cornerstones of next-generation therapeutic solutions, revolutionizing drug delivery, and paving the way for innovative, patient-centered treatments.

Introductory Review of Soft Implantable Bioelectronics Using Conductive and Functional Hydrogels and Hydrogel Nanocomposites

Interfaces between implantable bioelectrodes and tissues provide critical insights into the biological and pathological conditions of targeted organs, aiding diagnosis and treatment. While conventional bioelectronics, made from rigid materials like metals and silicon, have been essential for recording signals and delivering electric stimulation, they face limitations due to the mechanical mismatch between rigid devices and soft tissues. Recently, focus has shifted toward soft conductive materials, such as conductive hydrogels and hydrogel nanocomposites, known for their tissue-like softness, biocompatibility, and potential for functionalization. This review introduces these materials and provides an overview of recent advances in soft hydrogel nanocomposites for implantable electronics. It covers material strategies for conductive hydrogels, including both intrinsically conductive hydrogels and hydrogel nanocomposites, and explores key functionalization techniques like biodegradation, bioadhesiveness, injectability, and self-healing. Practical applications of these materials in implantable electronics are also highlighted, showcasing their effectiveness in real-world scenarios. Finally, we discuss emerging technologies and future needs for chronically implantable bioelectronics, offering insights into the evolving landscape of this field.

Development of a local controlled release system for therapeutic proteins in the treatment of skeletal muscle injuries and diseases

The present study aims to develop and characterize a controlled-release delivery system for protein therapeutics in skeletal muscle regeneration following an acute injury. The therapeutic protein, a membrane-GPI anchored protein called Cripto, was immobilized in an injectable hydrogel delivery vehicle for local administration and sustained release. The hydrogel was made of poly(ethylene glycol)-fibrinogen (PEG-Fibrinogen, PF), in the form of injectable microspheres. The PF microspheres exhibited a spherical morphology with an average diameter of approximately 100 micrometers, and the Cripto protein was uniformly entrapped within them. The release rate of Cripto from the PF microspheres was controlled by tuning the crosslinking density of the hydrogel, which was varied by changing the concentration of poly(ethylene glycol) diacrylate (PEG-DA) crosslinker. In vitro experiments confirmed a sustained-release profile of Cripto from the PF microspheres for up to 27 days. The released Cripto was biologically active and promoted the in vitro proliferation of mouse myoblasts. The therapeutic effect of PF-mediated delivery of Cripto in vivo was tested in a cardiotoxin (CTX)-induced muscle injury model in mice. The Cripto caused an increase in the in vivo expression of the myogenic markers Pax7, the differentiation makers eMHC and Desmin, higher numbers of centro-nucleated myofibers and greater areas of regenerated muscle tissue. Collectively, these results establish the PF microspheres as a potential delivery system for the localized, sustained release of therapeutic proteins toward the accelerated repair of damaged muscle tissue following acute injuries.

TSG6-Exo@CS/GP Attenuates Endometrium Fibrosis by Inhibiting Macrophage Activation in a Murine IUA Model

Intrauterine adhesion (IUA) is characterized by the formation of fibrous scar tissue within the uterine cavity, which significantly impacts female reproductive health and even leads to infertility. Unfortunately, severe cases of IUA currently lack effective treatments. This study presents a novel approach that utilizes tumor necrosis factor-(TNF) stimulated gene 6 (TSG6)-modified exosomes (Exos) in conjunction with an injectable thermosensitive hydrogel (CS/GP) to mitigate the occurrence of IUA by reducing endometrium fibrosis in a mouse IUA model. This study demonstrate that TSG6-modified Exos effectively inhibits the activation of inflammatory M1-like macrophages during the initial stages of inflammation and maintains the balance of macrophage phenotypes (M1/M2) during the repair phase. Moreover, TSG6 inhibits the interaction between macrophages and endometrial stromal fibroblasts, thereby preventing the activation of stromal fibroblasts into myofibroblasts. Furthermore, this research indicates that CS/GP facilitates the sustained release of TSG6-modified Exos, leading to a significant reduction in both the manifestations of IUA and the extent of endometrium fibrosis. Collectively, through the successful construction of CS/GP loaded with TSG6-modified Exos, a reduction in the occurrence and progression of IUA is achieved by mitigating endometrium fibrosis. Consequently, this approach holds promise for the treatment of IUA.

The role of hydrogels in the management of brain tumours: a narrative review

Conventional therapeutic techniques for brain tumours have limitations and side effects, necessitating the need for alternative treatment options. MRI-monitored therapeutic hydrogel systems show potential as a non-surgical approach for brain tumour treatment. Hydrogels have unique physical and chemical properties that make them promising for brain tumour treatment, including the ability to encapsulate therapeutic agents, provide sustained and controlled drug release, and overcome the blood-brain barrier for better penetration. By combining hydrogel systems with MRI techniques, it is possible to develop therapeutic approaches that provide real-time monitoring and controlled release of therapeutic agents. Surgical resection remains important, but there is a growing need for alternative approaches that can complement or replace traditional methods. The objective of this comprehensive narrative review is to evaluate the potential of MRI-monitored therapeutic hydrogel systems in non-surgical brain tumour treatment.

A Comprehensive Review of Hydrogel-Based Drug Delivery Systems: Classification, Properties, Recent Trends, and Applications

As adaptable biomaterials, hydrogels have shown great promise in several industries, which include the delivery of drugs, engineering of tissues, biosensing, and regenerative medicine. These hydrophilic polymer three-dimensional networks have special qualities like increased content of water, soft, flexible nature, as well as biocompatibility, which makes it excellent candidates for simulating the extracellular matrix and promoting cell development and tissue regeneration. With an emphasis on their design concepts, synthesis processes, and characterization procedures, this review paper offers a thorough overview of hydrogels. It covers the various hydrogel material types, such as natural polymers, synthetic polymers, and hybrid hydrogels, as well as their unique characteristics and uses. The improvements in hydrogel-based platforms for controlled drug delivery are examined. It also looks at recent advances in bioprinting methods that use hydrogels to create intricate tissue constructions with exquisite spatial control. The performance of hydrogels is explored through several variables, including mechanical properties, degradation behaviour, and biological interactions, with a focus on the significance of customizing hydrogel qualities for particular applications. This review paper also offers insights into future directions in hydrogel research, including those that promise to advance the discipline, such as stimuli-responsive hydrogels, self-healing hydrogels, and bioactive hydrogels. Generally, the objective of this review paper is to provide readers with a detailed grasp of hydrogels and all of their potential uses, making it an invaluable tool for scientists and researchers studying biomaterials and tissue engineering.