Translation of hyaluronic acid–based vitreous substitutes towards current regulations for medical devices

Development of injectable in situ hydrogels based on hyaluronic acid via Diels-Alder reaction for their antitumor activities studies

The objective of this study was to develop an injectable hydrogel based on furfuryl amine-conjugated hyaluronic acid (FA-conj-HA) and evaluate the in vivo anti-4 T1 tumor activity of doxorubicin-loaded hydrogel (DOX@FA-conj-HAgel). The cargo-free hydrogel (FA-conj-HAgel) was fabricated through a Diels-Alder reaction at 37 °C with FA-conj-HA as a gel material and four armed poly(ethylene glycol)2000-maleimide (4-arm-PEG2000-Mal) as a cross-linker. The bio-safety of FA-conj-HAgel were assessed, and the in vivo antitumor activity of DOX@FA-conj-HAgel was also investigated. Many 3D network structures were observed from scanning electron microscope (SEM) photograph, confirming the successful preparation of FA-conj-HAgel. The absence of cytotoxicity from FA-conj-HAgel was proved by the high viability of 4 T1 cells. In vivo bio-safety studies suggested that the obtained FA-conj-HAgel did not induce acute toxicity or other lesions in treated mice, confirming its high bio-safety. The reduced tumor volumes, hematoxylin-eosin staining (H&E), and TdT-mediated dUTP-biotin nick end labeling (TUNEL) analysis indicated the potent in vivo anti-4 T1 tumor effects of DOX@FA-conj-HAgel. In conclusion, the favorable bio-safety and potent antitumor activity of DOX@FA-conj-HAgel highlighted its potential application in oncological therapy.

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.