Abstract
A small library of thermoresponsive amphiphilic copolymers based on polylactide-block-poly((2-(2-methoxyethoxy)ethyl methacrylate)-co-(oligoethylene glycol methacrylate)) (PLA-b-P(DEGMA)-co-(OEGMA)), was synthesised by copper-mediated controlled radical polymerisation (CRP) with increasing ratios of OEGMA : DEGMA. These polymers were combined in two ways to form nanoparticles with controllable thermal transition temperatures as measured by particle aggregation. The first technique involved the blending of two (PLA-b-P(DEGMA)-co-(OEGMA)) polymers together prior to assembling nanoparticles (NPs). The second method involved mixing pre-formed nanoparticles of single (PLA-b-P(DEGMA)-co-(OEGMA)) polymers. The observed critical aggregation temperature Tt did not change in a linear relationship with the ratios of each copolymer either in the nanoparticles blended from different copolymers or in the mixtures of pre-formed nanoparticles. However, where co-polymer mixtures were based on (OEG)9MA ratios within 5-10 mole%, a linear relationship between (OEG)9MA composition in the blends and Tt was obtained. The data suggest that OEGMA-based copolymers are tunable over a wide temperature range given suitable co-monomer content in the linear polymers or nanoparticles. Moreover, the thermal transitions of the nanoparticles were reversible and repeatable, with the cloud point curves being essentially invariant across at least three heating and cooling cycles, and a selected nanoparticle formulation was found to be readily endocytosed in representative cancer cells and fibroblasts.
Highlights
Ruggero Foralosso,a Lee Moir,a Francesca Mastrotto,ab Luana Sasso,a Aleksandra Tchoryk,a Amjad Selo,a Anna Grabowska,c Marianne B
Scheme 1 Synthesis of thermoresponsive poly(lactic acid) (PLA)-b-P((DEGMA)-stat(OEGMA)) polymers used in this study
A range of polymers was produced with systematically varied mol : mol ratios of OEGMA and DEGMA (Scheme 1) via the AGET-ATRP route.[25]
Summary
Ruggero Foralosso,a Lee Moir,a Francesca Mastrotto,ab Luana Sasso,a Aleksandra Tchoryk,a Amjad Selo,a Anna Grabowska,c Marianne B. A small library of thermoresponsive amphiphilic copolymers based on polylactide-block-poly((2-(2-methoxyethoxy)ethyl methacrylate)-co-(oligoethylene glycol methacrylate)) (PLA-b-P(DEGMA)-co-(OEGMA)), was synthesised by copper-mediated controlled radical polymerisation (CRP) with increasing ratios of OEGMA : DEGMA These polymers were combined in two ways to form nanoparticles with controllable thermal transition temperatures as measured by particle aggregation. Paper change of surface-displayed polymers results in a loss in colloidal stability, which leads to particle precipitation or aggregation, dependent on concentration.[1] In more complex environments, for example in biological fluids or in tissue, the phase changes and increase in surface hydrophobicity can result in differential protein adsorption or cell membrane interaction.[13] These variations in bio-interfacial behaviour[14] have been the most widely explored, as nanoparticles with these properties have been shown to exhibit controllable cell attachment and endocytosis.[6,15]. There are the well-known issues in characterising polymers grown from the surface of nanoparticles, or estimating polymer surface coverage when the polymers are grafted to pre-formed nanoparticles
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