Properties of small molecular drug loading and diffusion in a fluorinated PEG hydrogel studied by ^1H molecular diffusion NMR and ^(19)F spin diffusion NMR

R_f-PEG (fluoroalkyl double-ended poly(ethylene glycol)) hydrogel is potentially useful as a drug delivery depot due to its advanced properties of sol–gel two-phase coexistence and low surface erosion. In this study, ^1H molecular diffusion nuclear magnetic resonance (NMR) and ^(19)F spin diffusion NMR were used to probe the drug loading and diffusion properties of the R_f-PEG hydrogel for small anticancer drugs, 5-fluorouracil (FU) and its hydrophobic analog, 1,3-dimethyl-5-fluorouracil (DMFU). It was found that FU has a larger apparent diffusion coefficient than that of DMFU, and the diffusion of the latter was more hindered. The result of ^(19)F spin diffusion NMR for the corresponding freeze-dried samples indicates that a larger portion of DMFU resided in the R_f core/IPDU intermediate-layer region (where IPDU refers to isophorone diurethane, as a linker to interconnect the R_f group and the PEG chain) than that of FU while the opposite is true in the PEG–water phase. To understand the experimental data, a diffusion model was proposed to include: (1) hindered diffusion of the drug molecules in the R_f core/IPDU-intermediate-layer region; (2) relatively free diffusion of the drug molecules in the PEG-water phase (or region); and (3) diffusive exchange of the probe molecules between the above two regions. This study also shows that molecular diffusion NMR combined with spin diffusion NMR is useful in studying the drug loading and diffusion properties in hydrogels for the purpose of drug delivery applications

Sports-Related Injuries of the Anterior Segment

Sports-related eye injury is a significant cause of morbidity and disability and accounts for a significant proportion of ocular trauma, especially in the young. Although some sports-related ocular injuries can be self-resolving and require little to no intervention, many other injuries have long-term sequelae that require extensive treatment and follow-up. A thorough evaluation of the mechanism of and circumstances surrounding the ocular injury is important to guide further management of the case. Blunt trauma has a significantly different pathophysiologic process compared to trauma by a sharp object, and the evaluation of the injury should be cognizant of the ocular trauma expected. The conjunctiva is most frequently involved in sports-related ocular injuries, and the nature of the conjunctival injury can often indicate involvement of other potential ocular structures. Examples of other anterior segment injuries that can result from sports-related ocular trauma include structural or functional damage to the cornea, iris injury leading to iris prolapse or laceration, ciliary body injury resulting in ciliary body detachment, lens injury resulting in cataract or subluxation/dislocation of the lens, and traumatic glaucoma. In this chapter, we provide a comprehensive review of the pathogenesis, clinical findings, treatment options, and prognosis of sports-related injuries of the anterior segment