Microphase Separation and Gelation of Methylcellulose in the Presence of Gallic Acid and NaCl as an In Situ Gel-Forming Drug Delivery System

Gallic acid: design of a pyrogallol-containing hydrogel and its biomedical applications

Polyphenol hydrogels have garnered widespread attention due to their excellent adhesion, antioxidant, and antibacterial properties. Gallic acid (GA) is a typical derivative of pyrogallol that is used as a hydrogel crosslinker or bioactive additive and can be used to make multifunctional hydrogels with properties superior to those of widely studied catechol hydrogels. Furthermore, compared to polymeric tannic acid, gallic acid is more suitable for chemical modification, thus broadening its range of applications. This review focuses on multifunctional hydrogels containing GA, aiming to inspire researchers in future biomaterial design. We first revealed the interaction mechanisms between GA molecules and between GA and polymers, analyzed the characteristics GA imparts to hydrogels and compared GA hydrogels with hydrogels containing catechol. Subsequently, in this paper, various methods of integrating GA into hydrogels and the applications of GA in biomedicine are discussed, finally assessing the current limitations and future development potential of GA. In summary, GA, a natural small molecule polyphenol with excellent functionality and diverse interaction modes, has great potential in the field of biomedical hydrogels.

Supramolecular hydrogels for wound repair and hemostasis

The unique network characteristics and stimuli responsiveness of supramolecular hydrogels have rendered them highly advantageous in the field of wound dressings, showcasing unprecedented potential. However, there are few reports on a comprehensive review of supramolecular hydrogel dressings for wound repair and hemostasis. This review first introduces the major cross-linking methods for supramolecular hydrogels, which includes hydrogen bonding, electrostatic interactions, hydrophobic interactions, host-guest interactions, metal ligand coordination and some other interactions. Then, we review the advanced materials reported in recent years and then summarize the basic principles of each cross-linking method. Next, we classify the network structures of supramolecular hydrogels before outlining their forming process and propose their potential future directions. Furthermore, we also discuss the raw materials, structural design principles, and material characteristics used to achieve the advanced functions of supramolecular hydrogels, such as antibacterial function, tissue adhesion, substance delivery, anti-inflammatory and antioxidant functions, cell behavior regulation, angiogenesis promotion, hemostasis and other innovative functions in recent years. Finally, the existing problems as well as future development directions of the cross-linking strategy, network design, and functions in wound repair and hemostasis of supramolecular hydrogels are discussed. This review is proposed to stimulate further exploration of supramolecular hydrogels on wound repair and hemostasis by researchers in the future.

Recent advances in cellulose, pectin, carrageenan and alginate-based oral drug delivery systems

Polymers-based drug delivery systems constitute one of the highly explored thrust areas in the field of the medicinal and pharmaceutical industries. In the past years, the properties of polymers have been modified in context to their solubility, release kinetics, targeted action site, absorption, and therapeutic efficacy. Despite the availability of diverse synthetic polymers for the bioavailability enhancement of drugs, the use of natural polymers is still highly recommended due to their easy availability, accessibility, and non-toxicity. The aim of the review is to provide the available literature of the last five years on oral drug delivery systems based on four natural polymers i.e., cellulose, pectin, carrageenan, and alginate in a concise and tabulated manner. In this review, most of the information is in tabulated form to provide easy accessibility to the reader. The data related to active pharmaceutical ingredients and supported components in different formulations of the mentioned polymers have been made available.

An Overview of Cellulose Derivatives-Based Dressings for Wound-Healing Management

Presently, notwithstanding the progress regarding wound-healing management, the treatment of the majority of skin lesions still represents a serious challenge for biomedical and pharmaceutical industries. Thus, the attention of the researchers has turned to the development of novel materials based on cellulose derivatives. Cellulose derivatives are semi-synthetic biopolymers, which exhibit high solubility in water and represent an advantageous alternative to water-insoluble cellulose. These biopolymers possess excellent properties, such as biocompatibility, biodegradability, sustainability, non-toxicity, non-immunogenicity, thermo-gelling behavior, mechanical strength, abundance, low costs, antibacterial effect, and high hydrophilicity. They have an efficient ability to absorb and retain a large quantity of wound exudates in the interstitial sites of their networks and can maintain optimal local moisture. Cellulose derivatives also represent a proper scaffold to incorporate various bioactive agents with beneficial therapeutic effects on skin tissue restoration. Due to these suitable and versatile characteristics, cellulose derivatives are attractive and captivating materials for wound-healing applications. This review presents an extensive overview of recent research regarding promising cellulose derivatives-based materials for the development of multiple biomedical and pharmaceutical applications, such as wound dressings, drug delivery devices, and tissue engineering.

A 3D Bioprinted Material That Recapitulates the Perivascular Bone Marrow Structure for Sustained Hematopoietic and Cancer Models

Translational medicine requires facile experimental systems to replicate the dynamic biological systems of diseases. Drug approval continues to lag, partly due to incongruencies in the research pipeline that traditionally involve 2D models, which could be improved with 3D models. The bone marrow (BM) poses challenges to harvest as an intact organ, making it difficult to study disease processes such as breast cancer (BC) survival in BM, and to effective evaluation of drug response in BM. Furthermore, it is a challenge to develop 3D BM structures due to its weak physical properties, and complex hierarchical structure and cellular landscape. To address this, we leveraged 3D bioprinting to create a BM structure with varied methylcellulose (M): alginate (A) ratios. We selected hydrogels containing 4% (w/v) M and 2% (w/v) A, which recapitulates rheological and ultrastructural features of the BM while maintaining stability in culture. This hydrogel sustained the culture of two key primary BM microenvironmental cells found at the perivascular region, mesenchymal stem cells and endothelial cells. More importantly, the scaffold showed evidence of cell autonomous dedifferentiation of BC cells to cancer stem cell properties. This scaffold could be the platform to create BM models for various diseases and also for drug screening.

Piribedil loaded thermo-responsive nasal in situ gelling system for enhanced delivery to the brain: formulation optimization, physical characterization, and in vitro and in vivo evaluation

Methyl cellulose (MC) based nasal in situ gels were developed to enhance the brain delivery of piribedil (PBD), an anti-Parkinson's drug. Different grades of MC and several solutes (NaCl, KCl, Na.Citrate, STPP, PEG-6000, sucrose, etc.) were screened to formulate thermo-responsive nasal in situ gelling systems. Formulations were evaluated for their sol-gel transition temperature and time, rheological behaviour, in vitro drug release, mucociliary clearance (MCC), ex vivo nasal toxicity, and in vivo brain availability studies in Wistar rats. Intranasal (i.n.) administration was carried out using a cannula-microtip setup to deliver PBD at the olfactory region of the nose. The concentration and viscosity grade of MC and also the concentration and type of solute used were found to affect the rheological behaviour of the formulations. Among the solutes tested, NaCl was found to be effective for formulating MC in situ gels. The developed in situ gels significantly delayed the MCC of PBD from the site of administration when compared with conventional suspension (p < 0.05). Further, formulations with higher gel strength showed lower in vitro drug release rate and longer intranasal residence (delayed MCC) (p < 0.05). The absolute brain availability (brain AUC_0-t) of PBD increased to 35.92% with i.n. delivery when compared to 4.71% with oral administration. Overall, it can be concluded that intranasal delivery of PBD is advantageous when compared to the currently practiced oral therapy. Graphical abstract.

Thermosensitive Poloxamer 407/Poly(Acrylic Acid) Hydrogels with Potential Application as Injectable Drug Delivery System

Thermosensitive hydrogels are of great interest for in situ gelling drug delivery. The thermosensitive vehicle with a gelation temperature in a range of 30-36°C would be convenient to be injected as liquid and transform into gel after injection. To prepare novel hydrogels gelling near body temperature, the gelation temperature of poloxamer 407 (PX) were tailored by mixing PX with poly(acrylic acid) (PAA). The gelation behaviors of PX/PAA systems as well as the interaction mechanism were investigated by tube inversion, viscoelastic, shear viscosity, DSC, SEM, and FTIR studies. The gelation temperature of the plain PX solutions at high concentration of 18, 20, and 22% (w/w) gelled at temperature below 28°C, which is out of the suitable temperature range. Mixing PX with PAA to obtain 18 and 20% (w/w) PX with 1% (w/w) PAA increased the gelation temperature to the desired temperature range of 30-36°C. The intermolecular entanglements and hydrogen bonds between PX and PAA may be responsible for the modulation of the gelation features of PX. The mixtures behaved low viscosity liquid at room temperature with shear thinning behavior enabling their injectability and rapidly gelled at body temperature. The gel strength increased, while the pore size decreased with increasing PX concentration. Metronidazole, an antibiotic used for periodontitis, was incorporated into the matrices, and the drug did not hinder their gelling ability. The gels showed the sustained drug release characteristic. The thermosensitive PX/PAA hydrogel could be a promising injectable in situ gelling system for periodontal drug delivery.