Controlling Growth Factor Diffusion by Modulating Water Content in Injectable Hydrogels

Diffusion-Limited Processes in Hydrogels with Chosen Applications from Drug Delivery to Electronic Components

Diffusion is one of the key nature processes which plays an important role in respiration, digestion, and nutrient transport in cells. In this regard, the present article aims to review various diffusion approaches used to fabricate different functional materials based on hydrogels, unique examples of materials that control diffusion. They have found applications in fields such as drug encapsulation and delivery, nutrient delivery in agriculture, developing materials for regenerative medicine, and creating stimuli-responsive materials in soft robotics and microrobotics. In addition, mechanisms of release and drug diffusion kinetics as key tools for material design are discussed.

Cell-instructive biomaterials in tissue engineering and regenerative medicine

The field of biomaterials aims to improve regenerative outcomes or scientific understanding for a wide range of tissue types and ailments. Biomaterials can be fabricated from natural or synthetic sources and display a plethora of mechanical, electrical, and geometrical properties dependent on their desired application. To date, most biomaterial systems designed for eventual translation to the clinic rely on soluble signaling moieties, such as growth factors, to elicit a specific cellular response. However, these soluble factors are often limited by high cost, convoluted synthesis, low stability, and difficulty in regulation, making the translation of these biomaterials systems to clinical or commercial applications a long and arduous process. In response to this, significant effort has been dedicated to researching cell-directive biomaterials which can signal for specific cell behavior in the absence of soluble factors. Cells of all tissue types have been shown to be innately in tune with their microenvironment, which is a biological phenomenon that can be exploited by researchers to design materials that direct cell behavior based on their intrinsic characteristics. This review will focus on recent developments in biomaterials that direct cell behavior using biomaterial properties such as charge, peptide presentation, and micro- or nano-geometry. These next generation biomaterials could offer significant strides in the development of clinically relevant medical devices which improve our understanding of the cellular microenvironment and enhance patient care in a variety of ailments.

Analysis of diffusion of plant metabolites from polyethylene glycol hydrogels using free volume theory

The present work aims to comprehensively analyze the diffusion of plant metabolites from the polyethylene glycol (PEG) hydrogels for controlled release applications. For this study, a mathematical model based on free volume theory has been utilized to simulate the diffusion of low molecular weight plant metabolites. The results demonstrate that the mesh size of the crosslinked network, thereby the diffusion coefficient of the natural compound can be computed using the current framework. The proposed model has also been validated using the experimental data. The diffusion period has been observed to vary within a wide range of 3.42 h for Cinnamaldehyde to 49.25 h for Grandinin. An empirical parametric relationship between the diffusion time and molecular weight of both the hydrogels and natural compounds is established. It appears that the reported modeling approach will be clinically useful for improving the design of the sustained drug delivery systems.

Molecular dynamics simulation of hyaluronic acid hydrogels: Effect of water content on mechanical and tribological properties

BACKGROUND AND OBJECTIVE

Recently conducted biomedical studies have shown that the drug diffusivity of hyaluronic acid hydrogel plays an important role in the treatment of joint diseases. The drug diffusivity is closely related to the water content of hydrogel. In addition, different water content will not only affect its mechanical and tribological properties, but also change the effect of drug release.

METHODS

In this work, a Molecular dynamics simulation was used to investigate the effect of water content on spatial distribution, tribological and mechanical properties of a hyaluronic acid hydrogel network. This paper focuses on the analysis and calculation of the radial distribution function of 20, 40, 60, and 80% water content model and the friction force and mechanical parameters under the influence of different load and friction speed.

RESULTS

The results show that at 20 and 40% water content, the spatial distribution is loose and the intermolecular force is not strong, resulting in a major lack in tribological and mechanical properties; whereas at 60 and 80% water content, the spatial distribution becomes gradually compact and the intermolecular force is gradually increased. The tribological and mechanical properties manifest a marked improvement.

CONCLUSIONS

The calculations reveal that the hydrogel model has the best wear resistance, pressure resistance, and plastic deformation resistance at 80% water content. In the range of 20-80% water content, the mechanical properties and friction properties of hydrogels become better and better with the increase of water content.

Pushing the Natural Frontier: Progress on the Integration of Biomaterial Cues toward Combinatorial Biofabrication and Tissue Engineering

The engineering of fully functional, biological-like tissues requires biomaterials to direct cellular events to a near-native, 3D niche extent. Natural biomaterials are generally seen as a safe option for cell support, but their biocompatibility and biodegradability can be just as limited as their bioactive/biomimetic performance. Furthermore, integrating different biomaterial cues and their final impact on cellular behavior is a complex equation where the outcome might be very different from the sum of individual parts. This review critically analyses recent progress on biomaterial-induced cellular responses, from simple adhesion to more complex stem cell differentiation, looking at the ever-growing possibilities of natural materials modification. Starting with a discussion on native material formulation and the inclusion of cell-instructive cues, the roles of shape and mechanical stimuli, the susceptibility to cellular remodeling, and the often-overlooked impact of cellular density and cell-cell interactions within constructs, are delved into. Along the way, synergistic and antagonistic combinations reported in vitro and in vivo are singled out, identifying needs and current lessons on the development of natural biomaterial libraries to solve the cell-material puzzle efficiently. This review brings together knowledge from different fields envisioning next-generation, combinatorial biomaterial development toward complex tissue engineering.

A bioinspired gelatin-hyaluronic acid-based hybrid interpenetrating network for the enhancement of retinal ganglion cells replacement therapy

Biomaterial-based cell replacement approaches to regenerative medicine are emerging as promising treatments for a wide array of profound clinical problems. Here we report an interpenetrating polymer network (IPN) composed of gelatin-hydroxyphenyl propionic acid and hyaluronic acid tyramine that is able to enhance intravitreal retinal cell therapy. By tuning our bioinspired hydrogel to mimic the vitreous chemical composition and mechanical characteristics we were able to improve in vitro and in vivo viability of human retinal ganglion cells (hRGC) incorporated into the IPN. In vivo vitreal injections of cell-bearing IPN in rats showed extensive attachment to the inner limiting membrane of the retina, improving with hydrogels stiffness. Engrafted hRGC displayed signs of regenerating processes along the optic nerve. Of note was the decrease in the immune cell response to hRGC delivered in the gel. The findings compel further translation of the gelatin-hyaluronic acid IPN for intravitreal cell therapy.

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.