Natural hydrogels R&D process: technical and regulatory aspects for industrial implementation

A review: Carrier-based hydrogels containing bioactive molecules and stem cells for ischemic stroke therapy

Ischemic stroke (IS), a cerebrovascular disease, is the leading cause of physical disability and death worldwide. Tissue plasminogen activator (tPA) and thrombectomy are limited by a narrow therapeutic time window. Although strategies such as drug therapies and cellular therapies have been used in preclinical trials, some important issues in clinical translation have not been addressed: low stem cell survival and drug delivery limited by the blood-brain barrier (BBB). Among the therapeutic options currently sought, carrier-based hydrogels hold great promise for the repair and regeneration of neural tissue in the treatment of ischemic stroke. The advantage lies in the ability to deliver drugs and cells to designated parts of the brain in an injectable manner to enhance therapeutic efficacy. Here, this article provides an overview of the use of carrier-based hydrogels in ischemic stroke therapy and focuses on the use of hydrogel scaffolds containing bioactive molecules and stem cells. In addition to this, we provide a more in-depth summary of the composition, physicochemical properties and physiological functions of the materials themselves. Finally, we also outline the prospects and challenges for clinical translation of hydrogel therapy for IS.

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.

Post-Stroke Recovery: A Review of Hydrogel-Based Phytochemical Delivery Systems

Stroke remains a leading cause of disability worldwide, underscoring the urgent need for novel and innovative therapeutic strategies to enhance neuroprotection, support regeneration, and improve functional recovery. Previous research has shown that phytochemicals such as curcumin, tannic acid, gallic acid, ginsenosides, resveratrol, and isorhamnetin display extensive neuroprotective properties, including antioxidant, anti-inflammatory, and anti-apoptotic effects. These natural compounds could also promote neurogenesis, angiogenesis, and the preservation of the blood-brain barrier. Despite their promising bioactivities, clinical application is often limited by poor solubility, bioavailability, and suboptimal pharmacokinetics. Hydrogels offer a promising solution by encapsulating and controlling the gradual release of these phytochemicals directly at the site of injury. Recent advancements in hydrogel formulations, constructed from biopolymers and functionalized using nanotechnological approaches, could significantly improve the solubility, stability, and targeted delivery of phytochemicals. Controlled release profiles from pH-sensitive and environment-responsive hydrogels could ensure that the compounds' therapeutic effects are optimally timed with individual and critical stages of post-stroke repair. Moreover, hydrogel scaffolds with tailored material properties and biocompatibility can create a favorable microenvironment, reducing secondary inflammation, enhancing tissue regeneration, and potentially improving functional and cognitive outcomes following stroke. This review explores the potential of integrating phytochemicals within hydrogel-based delivery systems specifically designed for post-stroke recovery. The design and synthesis of biocompatible, biodegradable hydrogels functionalized especially with phytochemicals and their applications are also discussed. Lastly, we emphasize the need for additional robust and translatable preclinical studies.

Hydrogel-Based Biointerfaces: Recent Advances, Challenges, and Future Directions in Human-Machine Integration

Human-machine interfacing (HMI) has emerged as a critical technology in healthcare, robotics, and wearable electronics, with hydrogels offering unique advantages as multifunctional materials that seamlessly connect biological systems with electronic devices. This review provides a detailed examination of recent advancements in hydrogel design, focusing on their properties and potential applications in HMI. We explore the key characteristics such as biocompatibility, mechanical flexibility, and responsiveness, which are essential for effective and long-term integration with biological tissues. Additionally, we highlight innovations in conductive hydrogels, hybrid and composite materials, and fabrication techniques such as 3D/4D printing, which allow for the customization of hydrogel properties to meet the demands of specific HMI applications. Further, we discuss the diverse classes of polymers that contribute to hydrogel conductivity, including conducting, natural, synthetic, and hybrid polymers, emphasizing their role in enhancing electrical performance and mechanical adaptability. In addition to material design, we examine the regulatory landscape governing hydrogel-based biointerfaces for HMI applications, addressing the key considerations for clinical translation and commercialization. An analysis of the patent landscape provides insights into emerging trends and innovations shaping the future of hydrogel technologies in human-machine interactions. The review also covers a range of applications, including wearable electronics, neural interfaces, soft robotics, and haptic systems, where hydrogels play a transformative role in enhancing human-machine interactions. Thereafter, the review addresses the challenges hydrogels face in HMI applications, including issues related to stability, biocompatibility, and scalability, while offering future perspectives on the continued evolution of hydrogel-based systems for HMI technologies.

3D Printing of Hydrogel Polysaccharides for Biomedical Applications: A Review

Additive manufacturing, also known as 3D printing, is becoming more and more popular because of its wide range of materials and flexibility in design. Layer by layer, 3D complex structures can be generated by the revolutionary computer-aided process known as 3D bioprinting. It is particularly crucial for youngsters and elderly patients and is a useful tool for tailored pharmaceutical therapy. A lot of research has been carried out recently on the use of polysaccharides as matrices for tissue engineering and medication delivery. Still, there is a great need to create affordable, sustainable bioink materials with high-quality mechanical, viscoelastic, and thermal properties as well as biocompatibility and biodegradability. The primary biological substances (biopolymers) chosen for the bioink formulation are proteins and polysaccharides, among the several resources utilized for the creation of such structures. These naturally occurring biomaterials give macromolecular structure and mechanical qualities (biomimicry), are generally compatible with tissues and cells (biocompatibility), and are harmonious with biological digesting processes (biodegradability). However, the primary difficulty with the cell-laden printing technique (bioprinting) is the rheological characteristics of these natural-based bioinks. Polysaccharides are widely used because they are abundant and reasonably priced natural polymers. Additionally, they serve as excipients in formulations for pharmaceuticals, nutraceuticals, and cosmetics. The remarkable benefits of biological polysaccharides-biocompatibility, biodegradability, safety, non-immunogenicity, and absence of secondary pollution-make them ideal 3D printing substrates. The purpose of this publication is to examine recent developments and challenges related to the 3D printing of stimuli-responsive polysaccharides for site-specific medication administration and tissue engineering.

Polysaccharide Hydrogels as Delivery Platforms for Natural Bioactive Molecules: From Tissue Regeneration to Infection Control

Polysaccharide-based hydrogels have emerged as indispensable materials in tissue engineering and wound healing, offering a unique combination of biocompatibility, biodegradability, and structural versatility. Indeed, their three-dimensional polymeric network and high water content closely resemble the natural extracellular matrix, creating a microenvironment for cell growth, differentiation, and tissue regeneration. Moreover, their intrinsic biodegradability, tunable chemical structure, non-toxicity, and minimal immunogenicity make them optimal candidates for prolonged drug delivery systems. Notwithstanding numerous advantages, these polysaccharide-based hydrogels are confronted with setbacks such as variability in material qualities depending on their source, susceptibility to microbial contamination, unregulated water absorption, inadequate mechanical strength, and unpredictable degradation patterns which limit their efficacy in real-world applications. This review summarizes recent advancements in the application of polysaccharide-based hydrogels, including cellulose, starch, pectin, zein, dextran, pullulan and hyaluronic acid as innovative solutions in wound healing, drug delivery, tissue engineering, and regenerative medicine. Future research should concentrate on optimizing hydrogel formulations to enhance their effectiveness in regenerative medicine and antimicrobial therapy.

Harnessing Peptide-Based Hydrogels for Enhanced Cartilage Tissue Engineering

Cartilage tissue engineering remains a formidable challenge due to its complex, avascular structure and limited regenerative capacity. Traditional approaches, such as microfracture, autografts, and stem cell delivery, often fail to restore functional tissue adequately. Recently, there has been a surge in the exploration of new materials that mimic the extracellular microenvironment necessary to guide tissue regeneration. This review investigates the potential of peptide-based hydrogels as an innovative solution for cartilage regeneration. These hydrogels, formed via supramolecular self-assembly, exhibit excellent properties, including biocompatibility, ECM mimicry, and controlled biodegradation, making them highly suitable for cartilage tissue engineering. This review explains the structure of cartilage and the principles of supramolecular and peptide hydrogels. It also delves into their specific properties relevant to cartilage regeneration. Additionally, this review presents recent examples and a comparative analysis of various peptide-based hydrogels used for cartilage regeneration. The review also addresses the translational challenges of these materials, highlighting regulatory hurdles and the complexities of clinical application. This comprehensive investigation provides valuable insights for biomedical researchers, tissue engineers, and clinical professionals aiming to enhance cartilage repair methodologies.

Hydrogel-Based Therapies for Ischemic and Hemorrhagic Stroke: A Comprehensive Review

Stroke remains the second leading cause of death and a major cause of disability worldwide, significantly impacting individuals, families, and healthcare systems. This neurological emergency can be triggered by ischemic events, including small vessel arteriolosclerosis, cardioembolism, and large artery atherothromboembolism, as well as hemorrhagic incidents resulting from macrovascular lesions, venous sinus thrombosis, or vascular malformations, leading to significant neuronal damage. The resultant motor impairment, cognitive dysfunction, and emotional disturbances underscore the urgent need for effective therapeutic interventions. Recent advancements in biomaterials, particularly hydrogels, offer promising new avenues for stroke management. Hydrogels, composed of three-dimensional networks of hydrophilic polymers, are notable for their ability to absorb and retain substantial amounts of water. Commonly used polymers in hydrogel formulations include natural polymers like alginate, chitosan, and collagen, as well as synthetic polymers such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylamide. Their customizable characteristics-such as their porosity, swelling behavior, mechanical strength, and degradation rates-make hydrogels ideal for biomedical applications, including drug delivery, cell delivery, tissue engineering, and the controlled release of therapeutic agents. This review comprehensively explores hydrogel-based approaches to both ischemic and hemorrhagic stroke therapy, elucidating the mechanisms by which hydrogels provide neuroprotection. It covers their application in drug delivery systems, their role in reducing inflammation and secondary injury, and their potential to support neurogenesis and angiogenesis. It also discusses current advancements in hydrogel technology and the significant challenges in translating these innovations from research into clinical practice. Additionally, it emphasizes the limited number of clinical trials utilizing hydrogel therapies for stroke and addresses the associated limitations and constraints, underscoring the need for further research in this field.

Insights into Translational and Biomedical Applications of Hydrogels as Versatile Drug Delivery Systems

Hydrogels are a network of crosslinked polymers which can hold a huge amount of water in their matrix. These might be soft, flexible, and porous resembling living tissues. The incorporation of different biocompatible materials and nanostructures into the hydrogels has led to emergence of multifunctional hydrogels with advanced properties. There are broad applications of hydrogels such as tissue culture, drug delivery, tissue engineering, implantation, water purification, and dressings. Besides these, it can be utilized in the field of medical surgery, in biosensors, targeted drug delivery, and drug release. Similarly, hyaluronic acid hydrogels have vast applications in biomedicines such as cell delivery, drug delivery, molecule delivery, micropatterning in cellular biology for tissue engineering, diagnosis and screening of diseases, tissue repair and stem cell microencapsulation in case of inflammation, angiogenesis, and other biological developmental processes. The properties like swellability, de-swellability, biodegradability, biocompatibility, and inert nature of the hydrogels in contact with body fluids, blood, and tissues make its tremendous application in the field of modern biomedicines nowadays. Various modifications in hydrogel formulations have widened their therapeutic applicability. These include 3D printing, conjugation, thiolation, multiple anchoring, and reduction. Various hydrogel formulations are also capable of dual drug delivery, dental surgery, medicinal implants, bone diseases, and gene and stem cells delivery. The presented review summarizes the unique properties of hydrogels along with their methods of preparation and significant biomedical applications as well as different types of commercial products available in the market and the regulatory guidance.

Chitosan-Based Hydrogel in the Management of Dermal Infections: A Review

The main objective of this review is to provide a comprehensive overview of the current evidence regarding the use of chitosan-based hydrogels to manage skin infections. Chitosan, a naturally occurring polysaccharide derived from chitin, possesses inherent antimicrobial properties, making it a promising candidate for treating various dermal infections. This review follows a systematic approach to analyze relevant studies that have investigated the effectiveness of chitosan-based hydrogels in the context of dermal infections. By examining the available evidence, this review aims to evaluate these hydrogels' overall efficacy, safety, and potential applications for managing dermal infections. This review's primary focus is to gather and analyze data from different recent studies about chitosan-based hydrogels combating dermal infections; this includes assessing their ability to inhibit the growth of microorganisms and reduce infection-related symptoms. Furthermore, this review also considers the safety profile of chitosan-based hydrogels, examining any potential adverse effects associated with their use. This evaluation is crucial to ensure that these hydrogels can be safely utilized in the management of dermal infections without causing harm to patients. The review aims to provide healthcare professionals and researchers with a comprehensive understanding of the current evidence regarding the use of chitosan-based hydrogels for dermal infection management. The findings from this review can contribute to informed decision-making and the development of potential treatment strategies in this field.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

Fabrication Strategies Towards Hydrogels for Biomedical Application: Chemical and Mechanical Insights

This review aims at giving selected chemical and mechanical insights on design criteria that should be taken into account in hydrogel production for biomedical applications. Particular emphasis will be given to the chemical aspects involved in hydrogel design: macromer chemical composition, cross-linking strategies and chemistry towards "conventional" and smart/stimuli responsive hydrogels. Mechanical properties of hydrogels in view of regenerative medicine applications will also be considered.

Polysaccharide 3D Printing for Drug Delivery Applications

3D printing, or additive manufacturing, has gained considerable interest due to its versatility regarding design as well as in the large choice of materials. It is a powerful tool in the field of personalized pharmaceutical treatment, particularly crucial for pediatric and geriatric patients. Polysaccharides are abundant and inexpensive natural polymers, that are already widely used in the food industry and as excipients in pharmaceutical and cosmetic formulations. Due to their intrinsic properties, such as biocompatibility, biodegradability, non-immunogenicity, etc., polysaccharides are largely investigated as matrices for drug delivery. Although an increasing number of interesting reviews on additive manufacturing and drug delivery are being published, there is a gap concerning the printing of polysaccharides. In this article, we will review recent advances in the 3D printing of polysaccharides focused on drug delivery applications. Among the large family of polysaccharides, the present review will particularly focus on cellulose and cellulose derivatives, chitosan and sodium alginate, printed by fused deposition modeling and extrusion-based printing.

Application of decellularized bone matrix as a bioscaffold in bone tissue engineering

Autologous bone grafts are commonly used as the gold standard to repair and regenerate diseased bones. However, they are strongly associated with postoperative complications, especially at the donor site, and increased surgical costs. In an effort to overcome these limitations, tissue engineering (TE) has been proposed as an alternative to promote bone repair. The successful outcome of tissue engineering depends on the microstructure and composition of the materials used as scaffold. Decellularized bone matrix-based biomaterials have been applied as bioscaffolds in bone tissue engineering. These biomaterials play an important role in providing the mechanical and physical microenvironment needed by cells to proliferate and survive. Decellularized extracellular matrix (dECM) can be used as a powder, hydrogel and electrospun scaffolds. These bioscaffolds mimic the native microenvironment due to their structure similar to the original tissue. The aim of this review is to highlight the bone decellularization techniques. Herein we discuss: (1) bone structure; (2) properties of an ideal scaffold; (3) the potential of decellularized bone as bioscaffolds; (4) terminal sterilization of decellularized bone; (5) cell removing confirmation in decellularized tissues; and (6) post decellularization procedures. Finally, the improvement of bone formation by dECM and the immunogenicity aspect of using the decellularized bone matrix are presented, to illustrate how novel dECM-based materials can be used as bioscaffold in tissue engineering. A comprehensive understanding of tissue engineering may allow for better incorporation of therapeutic approaches in bone defects allowing for bone repair and regeneration.

Towards clinical translation of 'second-generation' regenerative stroke therapies: hydrogels as game changers?

Stroke is an unmet clinical need with a paucity of treatments, at least in part because chronic stroke pathologies are prohibitive to 'first-generation' stem cell-based therapies. Hydrogels can remodel the hostile stroke microenvironment to aid endogenous and exogenous regenerative repair processes. However, no clinical trials have yet been successfully commissioned for these 'second-generation' hydrogel-based therapies for chronic ischaemic stroke regeneration. This review recommends a path forward to improve hydrogel technology for future clinical translation for stroke. Specifically, we suggest that a better understanding of human host stroke tissue-hydrogel interactions in addition to the effects of scaling up hydrogel volume to human-sized cavities would help guide translation of these second-generation regenerative stroke therapies.

Biomedical Application, Patent Repository, Clinical Trial and Regulatory Updates on Hydrogel: An Extensive Review

Hydrogels are known for their leading role in biomaterial systems involving pharmaceuticals that fascinate material scientists to work on the wide variety of biomedical applications. The physical and mechanical properties of hydrogels, along with their biodegradability and biocompatibility characteristics, have made them an attractive and flexible tool with various applications such as imaging, diagnosis and treatment. The water-cherishing nature of hydrogels and their capacity to swell-contingent upon a few ecological signals or the simple presence of water-is alluring for drug conveyance applications. Currently, there are several problems relating to drug delivery, to which hydrogel may provide a possible solution. Hence, it is pertinent to collate updates on hydrogels pertaining to biomedical applications. The primary objective of this review article is to garner information regarding classification, properties, methods of preparations, and of the polymers used with particular emphasis on injectable hydrogels. This review also covers the regulatory and other commerce specific information. Further, it enlists several patents and clinical trials of hydrogels with related indications and offers a consolidated resource for all facets associated with the biomedical hydrogels.

Multifunctional Hydrogel Nanocomposites for Biomedical Applications

Hydrogels are used for various biomedical applications due to their biocompatibility, capacity to mimic the extracellular matrix, and ability to encapsulate and deliver cells and therapeutics. However, traditional hydrogels have a few shortcomings, especially regarding their physical properties, thereby limiting their broad applicability. Recently, researchers have investigated the incorporation of nanoparticles (NPs) into hydrogels to improve and add to the physical and biochemical properties of hydrogels. This brief review focuses on papers that describe the use of nanoparticles to improve more than one property of hydrogels. Such multifunctional hydrogel nanocomposites have enhanced potential for various applications including tissue engineering, drug delivery, wound healing, bioprinting, and biowearable devices.

Injectable Hydrogels: From Laboratory to Industrialization

The transfer of some innovative technologies from the laboratory to industrial scale is many times not taken into account in the design and development of some functional materials such as hydrogels to be applied in the biomedical field. There is a lack of knowledge in the scientific field where many aspects of scaling to an industrial process are ignored, and products cannot reach the market. Injectable hydrogels are a good example that we have used in our research to show the different steps needed to follow to get a product in the market based on them. From synthesis and process validation to characterization techniques used and assays performed to ensure the safety and efficacy of the product, following regulation, several well-defined protocols must be adopted. Therefore, this paper summarized all these aspects due to the lack of knowledge that exists about the industrialization of injectable products with the great importance that it entails, and it is intended to serve as a guide on this area to non-initiated scientists. More concretely, in this work, the characteristics and requirements for the development of injectable hydrogels from the laboratory to industrial scale is presented in terms of (i) synthesis techniques employed to obtain injectable hydrogels with tunable desired properties, (ii) the most common characterization techniques to characterize hydrogels, and (iii) the necessary safety and efficacy assays and protocols to industrialize and commercialize injectable hydrogels from the regulatory point of view. Finally, this review also mentioned and explained a real example of the development of a natural hyaluronic acid hydrogel that reached the market as an injectable product.