Polymer-based thermoresponsive hydrogels for controlled drug delivery

Recent advances on thermosensitive hydrogels-mediated precision therapy

Precision therapy has become the preferred choice attributed to the optimal drug concentration in target sites, increased therapeutic efficacy, and reduced adverse effects. Over the past few years, sprayable or injectable thermosensitive hydrogels have exhibited high therapeutic potential. These can be applied as cell-growing scaffolds or drug-releasing reservoirs by simply mixing in a free-flowing sol phase at room temperature. Inspired by their unique properties, thermosensitive hydrogels have been widely applied as drug delivery and treatment platforms for precision medicine. In this review, the state-of-the-art developments in thermosensitive hydrogels for precision therapy are investigated, which covers from the thermo-gelling mechanisms and main components to biomedical applications, including wound healing, anti-tumor activity, osteogenesis, and periodontal, sinonasal and ophthalmic diseases. The most promising applications and trends of thermosensitive hydrogels for precision therapy are also discussed in light of their unique features.

Exploring the Landscape of Hydrogel Therapy for Spinal Cord Injury: A Bibliometric and Visual Analysis (1991-2023)

BACKGROUND

This study aimed to conduct a bibliometric analysis of the literature on hydrogel therapy for spinal cord injury to visualize the research status, identify hotspots, and explore the development trends in this field.

METHODS

Web of science Core Collection database was searched for relevant studies published between January 1991 and December 2023. Data such as journal title, author information, institutional affiliation, country, citation, and keywords were extracted. Bibliometrix, CiteSpace, and VOSviewer were used to perform bibliometric analysis of the retrieved data.

RESULTS

A total of 1099 articles pertaining to hydrogel therapy for spinal cord injury were retrieved, revealing an upward trajectory in both annual publication volume and cumulative publication volume. Biomaterials emerged as the journal with the highest number of publications and the most rapid cumulative publication growth, contributing 84 articles. Among authors, Shoichet MS stood out with the highest number of publications and citations, totaling 66 articles. The University of Toronto led in institutional contributions with 65 publications, while China dominated in country-specific publications, accounting for 374 articles. However, to foster significant academic achievements, it is imperative for diverse authors, institutions, and countries to enhance collaboration. Current research in this field concentrates on scaffold architecture, nerve growth factor, the fibrotic microenvironment, and guidance channels. Simultaneously, upcoming research directions prioritize 3D bioprinting, injectable hydrogel, inflammation, and nanoparticles within the realm of hydrogel therapy for spinal cord injuries.

CONCLUSIONS

In summary, this study provided a comprehensive analysis of the current research status and frontiers of hydrogel therapy for spinal cord injury. The findings provide a foundation for future research and clinical translation efforts of hydrogel therapy in this field.

Advancements in hydrogel-based drug delivery systems for the treatment of inflammatory bowel disease: a review

Inflammatory bowel disease (IBD) is a chronic disorder that affects millions of individuals worldwide. However, current drug therapies for IBD are plagued by significant side effects, low efficacy, and poor patient compliance. Consequently, there is an urgent need for novel therapeutic approaches to alleviate IBD. Hydrogels, three-dimensional networks of hydrophilic polymers with the ability to swell and retain water, have emerged as promising materials for drug delivery in the treatment of IBD due to their biocompatibility, tunability, and responsiveness to various stimuli. In this review, we summarize recent advancements in hydrogel-based drug delivery systems for the treatment of IBD. We first identify three pathophysiological alterations that need to be addressed in the current treatment of IBD: damage to the intestinal mucosal barrier, dysbiosis of intestinal flora, and activation of inflammatory signaling pathways leading to disequilibrium within the intestines. Subsequently, we discuss in depth the processes required to prepare hydrogel drug delivery systems, from the selection of hydrogel materials, types of drugs to be loaded, methods of drug loading and drug release mechanisms to key points in the preparation of hydrogel drug delivery systems. Additionally, we highlight the progress and impact of the hydrogel-based drug delivery system in IBD treatment through regulation of physical barrier immune responses, promotion of mucosal repair, and improvement of gut microbiota. In conclusion, we analyze the challenges of hydrogel-based drug delivery systems in clinical applications for IBD treatment, and propose potential solutions from our perspective.

Electroactive Polymers for On-Demand Drug Release

Conductive materials have played a significant role in advancing society into the digital era. Such materials are able to harness the power of electricity and are used to control many aspects of daily life. Conductive polymers (CPs) are an emerging group of polymers that possess metal-like conductivity yet retain desirable polymeric features, such as processability, mechanical properties, and biodegradability. Upon receiving an electrical stimulus, CPs can be tailored to achieve a number of responses, such as harvesting energy and stimulating tissue growth. The recent FDA approval of a CP-based material for a medical device has invigorated their research in healthcare. In drug delivery, CPs can act as electrical switches, drug release is achieved at a flick of a switch, thereby providing unprecedented control over drug release. In this review, recent developments in CP as electroactive polymers for voltage-stimuli responsive drug delivery systems are evaluated. The review demonstrates the distinct drug release profiles achieved by electroactive formulations, and both the precision and ease of stimuli response. This level of dynamism promises to yield "smart medicines" and warrants further research. The review concludes by providing an outlook on electroactive formulations in drug delivery and highlighting their integral roles in healthcare IoT.

On the role of polymeric hydrogels in the thermal response of gold nanorods under NIR laser irradiation

Hydrogels are 3D cross-linked networks of polymeric chains designed to be used in the human body. Nowadays they find widespread applications in the biomedical field and are particularly attractive as drug delivery vectors. However, despite many good results, their release performance is sometimes very quick and uncontrolled, being forced by the high in vivo clearance of body fluids. In this direction, the development of novel responsive nanomaterials promises to overcome the drawbacks of common hydrogels, inducing responsive properties in three-dimensional polymeric devices. In this study, we synthesized and then loaded gold nanorods (Au NRs) within an agarose-carbomer (AC)-based hydrogel obtained from a microwave-assisted polycondensation reaction between carbomer 974P and agarose. The photothermal effect of the composite device was quantified in terms of maximum temperature and spatial-temporal temperature distribution, also during consecutive laser irradiations. This work shows that composite Au NRs loaded within AC hydrogels can serve as a stable photothermal treatment agent with enhanced photothermal efficiency and good thermal stability after consecutive laser irradiations. These results confirm that the composite system produced can exhibit an enhanced thermal effect under NIR laser irradiation, which is expected to lead to great therapeutic advantages for the localized treatment of different diseases.

Hydrogel drug delivery systems for minimally invasive local immunotherapy of cancer

Although systemic immunotherapy has achieved durable responses and improved survival for certain patients and cancer types, low response rates and immune system-related systemic toxicities limit its overall impact. Intratumoral (intralesional) delivery of immunotherapy is a promising technique to combat mechanisms of tumor immune suppression within the tumor microenvironment and reduce systemic drug exposure and associated side effects. However, intratumoral injections are prone to variable tumor drug distribution and leakage into surrounding tissues, which can compromise efficacy and contribute to toxicity. Controlled release drug delivery systems such as in situ-forming hydrogels are promising vehicles for addressing these challenges by providing improved spatio-temporal control of locally administered immunotherapies with the goal of promoting systemic tumor-specific immune responses and abscopal effects. In this review we will discuss concepts, applications, and challenges in local delivery of immunotherapy using controlled release drug delivery systems with a focus on intratumorally injected hydrogel-based drug carriers.

[Latest Findings on Hydrogel Drug Delivery Systems in the Treatment of Periodontitis]

Hydrogel drug delivery systems possess unique structures and properties and hence can be injected and retained in the periodontal pocket for slow and controlled release of medications with antibacterial, anti-inflammatory, and periodontal tissue regeneration-promotional effects. Due to their safety, practicability, and effectiveness, they show great potential in the treatment of periodontitis. In this paper, we gave an overview of hydrogel drug delivery systems in the treatment of periodontitis, summing up the classification and forms of the drugs delivered and the strengths and weaknesses of common types of hydrogel matrixes. In addition, we discussed properties required for hydrogel drug delivery systems applicable in the treatment of periodontitis, including a certain level of viscosity, suitable degradation cycle, and temperature sensitivity. Finally, we summarized the stimulus responsiveness types of hydrogel drug delivery systems applicable in the treatment of periodontitis, including pH-responsiveness, enzyme-responsiveness, reactive oxygen species-responsiveness, light-responsiveness, and sugar-responsiveness. In the future, researchers should make further investigation into the clinical efficacy of hydrogel drug delivery systems and promote their translation into clinical applications. Additionally, hydrogel drug delivery systems carrying biologic drugs could be further investigated to promote advancement in the field of periodontal tissue regeneration. Furthermore, the response sources, realization strategies, and safe preparation methods of smart hydrogel drug delivery systems should also be further clarified and explored to achieve drug delivery of better efficiency and safety. In addition to drug delivery, hydrogel matrixes with medicinal values also show great promises.

Probing Pharmaceutical Strategies to Promote the Skin Delivery of Asiatic Acid from Hydrogels: Enhancement Effects of Organic Amine Counterions, Chemical Enhancers, and Microneedle Pretreatment

Asiatic acid (AA) is a pentacyclic triterpene isolated from Centella asiatica, holding great promise for treating a variety of skin disorders. However, the dermal application of AA is limited by its poor solubility and permeability. This study aimed to identify a hydrogel formulation for AA and improve its skin penetration by various penetration enhancement methods. Four kinds of hydrogel bases were selected to prepare the AA hydrogel, in which different organic amines and chemical enhancers were incorporated in combination with microneedle pretreatment. The results showed that AA had good release profiles in the presence of hyaluronic acid as the hydrogel base and organic amines as the counter-ions. Diethylamine and Span 80 could promote drug penetration into the skin, and pretreatment with microneedles could further increase the drug permeability. In conclusion, the optimized hyaluronic acid hydrogel has great potential for use in the topical delivery of AA, and its penetration via the skin can be further improved by different pharmaceutical approaches.