A nanocomposite contact lens for the delivery of hydrophilic protein drugs

Corneal sustained delivery of hyaluronic acid from nanofiber-containing ring-implanted contact lens

Dry eye syndrome, as a persist corneal epithelial defect (PED), is an inconvenient ocular disorder that is generally treated by high-dosage, conventional eye drops. Addressing low efficacy and rather restricted bioavailability of the conventional eye drops, drug-eluting contact lenses (CLs) are widely used as alternatives in ophthalmic drug delivery applications. In the present study, a nanofiber-containing ring implant poly (vinyl alcohol) (PVA) hydrogel is designed as a carrier for hyaluronic acid (HA) delivery. hyaluronic acid is physically encapsulated in a nanofiber-containing ring-shaped hydrogel with a 2 mm width that is implanted in the final CLs hydrogel. The designed CL has 59% porosity, 275% swelling ratio and undergoes no weight loss at physiological conditions in14 days. In-vitro release studies were performed on the CLs with and without nanofibers. The results showed that nanofiber incorporation in the designed CL was highly influential in decreasing burst release and supported sustained release of HA over 14 days. In addition, nanofiber incorporation in the designed system strengthened the lens, and the young modulus of the PVA hydrogel increased from 6 to 10 kPa. Cell viability study also revealed no cell cytotoxicity and cell attachment. Overall, the study demonstrated the effective role of nanofibers in the physical strengthening of the CL. Also, the designed system holds promise as a potential candidate for HA delivery over an extended period for treating dry eye syndrome.

Cross-linked Porous Gelatin Microparticles with Tunable Shape, Size, and Porosity

Gelatin particles are relevant to many applications in the biomedical field due to their excellent biocompatibility and versatility. When prepared by double emulsion methods, porous microparticles with different architectures can be obtained. Controlling the shape, size, porosity, swelling, and stability against dissolution is fundamental toward their application under physiological conditions. We prepared porous gelatin microparticles from oil-in-water-in-oil emulsions, modifying the gelatin/surfactant ratio and the stirring speed. The effect on structural properties, including surface and inner porosities, was thoroughly assessed by multiple microscopy techniques (optical, electron, and confocal Raman). Selected samples were cross-linked with glutaraldehyde or glyceraldehyde, and their swelling properties and stability against dissolution were evaluated, while the influence of the cross-linking at the nanoscale was studied by scattering of X-rays. Depending on the preparation protocol, we obtained particles with different shapes (irregular or spherical), radii within ∼40 to 90 μm, and porosities up to 10 μm. The cross-linking extends the stability in water from a few minutes up to several days while the swelling ability and the mesh size at the nanoscale of the gelatin network are preserved. The analysis of the experimental results as a function of the preparation parameters demonstrates that microparticles with tunable features can be designed.

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.

Intravitreal hydrogels for sustained release of therapeutic proteins

This review highlights how hydrogel formulations can improve intravitreal protein delivery to the posterior segment of the eye in order to increase therapeutic outcome and patient compliance. Several therapeutic proteins have shown excellent clinical successes for the treatment of various intraocular diseases. However, drug delivery to the posterior segment of the eye faces significant challenges due to multiple physiological barriers preventing drugs from reaching the retina, among which intravitreal protein instability and rapid clearance from the site of injection. Hence, frequent injections are required to maintain therapeutic levels. Moreover, because the world population ages, the number of patients suffering from ocular diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) is increasing and causing increased health care costs. Therefore, there is a growing need for suitable delivery systems able to tackle the current limitations in retinal protein delivery, which also may reduce costs. Hydrogels have shown to be promising delivery systems capable of sustaining release of therapeutic proteins and thus extending their local presence. Here, an extensive overview of preclinically developed intravitreal hydrogels is provided with attention to the rational design of clinically useful intravitreal systems. The currently used polymers, crosslinking mechanisms, in vitro/in vivo models and advancements are discussed together with the limitations and future perspective of these biomaterials.

Biomaterials and controlled release strategy for epithelial wound healing

The skin and cornea are tissues that provide protective functions. Trauma and other environmental threats often cause injuries, infections and damage to these tissues, where the degree of injury is directly correlated to the recovery time. For example, a superficial skin or corneal wound may recover within days; however, more severe injuries can last up to several months and may leave scarring. Thus, therapeutic strategies have been introduced to enhance the wound healing efficiency and quality. Although the skin and cornea share similar anatomic structures and wound healing process, therapeutic agents and formulations for skin and cornea wound healing differ in accordance with the tissue and wound type. In this review, we describe the anatomy and epithelial wound healing processes of the skin and cornea, and summarize the therapeutic molecules that are beneficial to the respective regeneration process. In addition, biomaterial scaffolds that inherently possess bioactive properties or modified with therapeutic molecules for topical controlled release and enhanced wound healing efficiency are also discussed.

Hydrogels for sustained delivery of biologics to the back of the eye

Hydrogels are water-laden polymer networks that have been used for myriad biological applications. By controlling the chemistry through which a hydrogel is constructed, a wide range of chemical and physical properties can be accessed, making them an attractive class of biomaterials. In this review, we cover the application of hydrogels for sustained delivery of biologics to the back of the eye. In adapting hydrogels to this purpose, success is dependent on careful consideration of material properties, route of administration, means of injection, and control of drug efflux, all of which are addressed. We also provide a perspective on clinical and chemistry, manufacturing and controls (CMC) considerations that are integral to the development of an ocular hydrogel delivery system.

Special properties of luminescent magnetic NaGdF4:Yb3+, Er3+ upconversion nanocubes with surface modifications

Gadolinium-based upconversion nanocubes with amine surface modification are made by a one-pot process. The interfacial effect on their behaviors are observed.

Gelatin-based particulate systems in ocular drug delivery

Despite all scientists efforts exerted over the past years, the ocular delivery of drugs remains a great challenge due to several barriers and hurdles faced by this kind of administration. The exploitation of gelatin that has a long history of safe use in pharmaceuticals and which is considered as a GRAS (Generally Regarded As Safe) material by the FDA was not fully achieved in this field. This review summarizes the recent studies and findings where gelatin-based micro- and nanoparticles were used for successful ocular delivery aiming at drawing the attention of researchers and scientists to this valuable biomaterial that has not been fully explored.

Gelatin-Based Materials in Ocular Tissue Engineering

Gelatin has been used for many years in pharmaceutical formulation, cell culture and tissue engineering on account of its excellent biocompatibility, ease of processing and availability at low cost. Over the last decade gelatin has been extensively evaluated for numerous ocular applications serving as cell-sheet carriers, bio-adhesives and bio-artificial grafts. These different applications naturally have diverse physical, chemical and biological requirements and this has prompted research into the modification of gelatin and its derivatives. The crosslinking of gelatin alone or in combination with natural or synthetic biopolymers has produced a variety of scaffolds that could be suitable for ocular applications. This review focuses on methods to crosslink gelatin-based materials and how the resulting materials have been applied in ocular tissue engineering. Critical discussion of recent innovations in tissue engineering and regenerative medicine will highlight future opportunities for gelatin-based materials in ophthalmology.