Super-fast in situ formation of hydrogels based on multi-arm functional polyethylene glycols as endotamponade substitutes

Desired properties of polymeric hydrogel vitreous substitute

Vitreous replacement is a commonly employed method for treating a range of ocular diseases, including posterior vitreous detachment, complex retinal detachment, diabetic retinopathy, macular hole, and ocular trauma. Various clinical substitutes for vitreous include air, expandable gas, silicone oil, heavy silicone oil, and balanced salt solution. However, these substitutes have drawbacks such as short retention time, cytotoxicity, high intraocular pressure, and the formation of cataracts, rendering them unsuitable for long-term treatment. Polymeric hydrogels possess the potential to serve as ideal vitreous substitutes due to their structure-mimicking to natural vitreous and adjustable mechanical properties. Replacement with hydrogels as the tamponade can help maintain the shape of the eyeball, apply pressure to the detached retina, and ensure the metabolic transport of substances without impairing vision. This literature review examines the required properties of artificial vitreous, including the optical properties, rheological properties, expansive force action, and physiological and biochemical functions of chemically and physically crosslinked hydrogels. The strategies for enhancing the biocompatibility and injectability of hydrogels are also summarized and discussed. From a clinical ophthalmology perspective, this paper presents the latest developments in vitreous replacement, providing clinicians with a comprehensive understanding of hydrogel clinical applications, which offers guidance for future design directions and methodologies for hydrogel development.

Applications and Recent Developments of Hydrogels in Ophthalmology

Hydrogels are a type of functional polymer material with a three-dimensional network structure composed of physically or chemically cross-linked polymers. All hydrogels have two common features: first, their structure contains a large number of hydrophilic groups; therefore, they have a high water content and can swell in water. Second, they have good regulation, and the physical and chemical properties of their cross-linked network can be changed by environmental factors and deliberate modification methods. In recent years, the application of hydrogels in ophthalmology has gradually attracted attention. By selecting an appropriate composition and cross-linking mode, hydrogels can be used in different fields for various applications, such as gel eye drops, in situ gel preparation, intravitreal injection, and corneal contact lenses. This Review provides a detailed introduction to the classification of hydrogels and their applications in glaucoma, vitreous substitutes, fundus diseases, corneal contact lenses, corneal diseases, and cataract surgery.

Super-Rapid In Situ Formation of a Silver Ion-Induced Supramolecular Hydrogel with Efficient Antibacterial Activity for Root Canal Disinfection

Supramolecular hydrogels prepared using low-molecular-weight gelators have attracted considerable attention for biomedical applications. However, in situ supramolecular hydrogels are limited in terms of their prolonged gelation time and/or unstable nature at high temperatures. In this study, we constructed a stable supramolecular Ag-isoG hydrogel through super-rapid in situ formation, wherein hydrogelation process occurred instantaneously upon mixing isoG and Ag⁺ within 1 s under ambient conditions. Interestingly, unlike most nucleoside-based supramolecular hydrogels, this Ag-isoG hydrogel remains stable even at a high temperature (100 °C). Moreover, the as-designed hydrogel demonstrated significant antibacterial activity against Staphylococcus aureus and the oral bacterium Streptococcus mutans owing to the strong chelating ability of Ag ions, and the hydrogel exhibited relatively low cytotoxicity in root canal and an easy removal feature by saline. The hydrogel was then applied to a root canal infection model, which demonstrated strong antibacterial activity against Enterococcus faecalis, with performance even better than that of the regular calcium hydroxide paste. This feature makes the Ag-isoG hydrogel a prospective alternative material as intracanal medicaments for root canal treatment.