Complicated cases of retinal detachment can be treated with silicone oil tamponades. There is the potential for silicone oil tamponades to have adjunctive drug releasing behaviour within the eye, however the lipophilic nature of silicone oil limits the number of drugs that are suitable, and drug release from the hydrophobic reservoir is uncontrolled. Here, a radiometric technique was developed to accurately measure drug solubility in silicone oil and measure release into culture media. All‐trans retinoic acid (atRA), a lipophilic drug known to act as an anti‐proliferative within the eye, was used throughout this work. Chain‐end modification of polydimethylsiloxane with atRA produced a polydimethylsiloxane retinoate (PDMS‐atRA), which was used as an additive to silicone oil to modify the solvent environment within the silicone oil and the distribution coefficient. Blends of PDMS‐atRA and silicone oil containing different concentrations of free atRA were produced. The presence of PDMS‐atRA in silicone oil had a positive effect on atRA solubility and the longevity of release in vitro. The drug release period was independent of atRA starting concentration and dependent on the PDMS‐atRA concentration in the blend. A clinically relevant release period of atRA over 7 weeks from a silicone oil blend with PDMS‐atRA was observed. © 2018 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 938–946

In a number of cases of retinal detachment, treatment may require the removal of the vitreous humour within the eye and replacement with silicone oil to aid healing of the retina. The insertion of silicone oil offers the opportunity to also deliver drugs to the inside of the eye; however, drug solubility in silicone oil is poor and release from this hydrophobic drug reservoir is not readily controlled. Here, we have designed a range of statistical graft copolymers that incorporate dimethylsiloxane and ethylene glycol repeat units within the side chains, allowing short chains of oligo(ethylene glycol) to be solubilised within silicone oil and provide hydrogen bond acceptor sites to interact with acid functional drug molecules. Our hypothesis included the potential for such interactions to be able to delay/control drug release and for polymer architecture and composition to play a role in the silicone oil miscibility of the targeted polymers. This strategy has been successfully demonstrated using both ibuprofen and all-trans retinoic acid; drugs with anti-inflammatory and anti-proliferation activity. After the copolymers were shown to be non-toxic to retinal pigment epithelial cells, studies of drug release using radiochemical approaches showed that the presence of 10v/v% of a linear graft copolymer could extend ibuprofen release over three-fold (from 3days to >9days) whilst the release of all-trans retinoic from the silicone oil phase was extended to >72days. These timescales are highly clinically relevant showing the potential to tune drug delivery during the healing process and offer an efficient means to improve patient outcomes.

Mucoadhesion and mucus-sensitive materials have many applications. Redundant chain-ends within branched polymer emulsifiers have been functionalized with thiols, without compromising emulsion stability, to create mucus-interacting emulsions.

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