Enhanced distance-dependent fluorescence quenching using size tuneable core shell silica nanoparticles

Silica nanoparticles (SNPs) have been used as favoured platforms for sensor, drug delivery and biological imaging applications, due to their ease of synthesis, size-control and bespoke physico-chemical properties. In this study, we have developed a protocol for the synthesis of size-tuneable SNPs, with diameters ranging from 20 nm to 500 nm, through the optimisation of experimental components required for nanoparticle synthesis. This protocol was also used to prepare fluorescent SNPs, via covalent linkages of fluorophores, to the nanoparticle matrix using 3-aminopropyltriethoxysilane (APTES). This enabled the fabrication of ratiometric, fluorescent, pH-sensitive nanosensors (75 nm diameter) composed SNPs covalently linked to two pH-sensitive fluorescent dyes Oregon Green (OG) and 5(6)-carboxyfluorescein (FAM) and a reference fluorescent dye 5-(6)-carboxytetramethylrhodamine (TAMRA), extending the dynamic range of measurement from pH 3.5 to 7.5. In addition, size-tuneable, core-shell SNPs, covalently linked to a fluorescent TAMRA core were synthesised to investigate distance-dependant fluorescence quenching between TAMRA and black hole quencher 2 (BHQ2®) using nanometre-sized silica shells as physical spacers. The results showed a significant fluorescence quenching could be observed over greater distances than that reported for the classical distance-dependent molecular fluorescence quenching techniques, e.g. the Förster (fluorescence) resonance energy transfer (FRET). The methods and protocols we have detailed in this manuscript will provide the basis for the reproducible production of size tunable SNPs, which will find broad utility in the development of sensors for biological applications

From 'fixed dose combinations' to 'a dynamic dose combiner': 3D printed bi-layer antihypertensive tablets

There is an increased evidence for treating hypertension by a combination of two or more drugs. Increasing the number of daily intake of tablets has been reported to negatively affect the compliance by patients. Therefore, numerous fixed dose combinations (FDCs) have been introduced to the market. However, the inherent rigid nature of FDCs does not allow titration of the dose of each single component for individual patient needs. In this work, flexible dose combinations of two anti-hypertensive drugs in a single bilayer tablet with a range of doses were fabricated using dual fused deposition modelling (FDM) 3D printer. Enalapril maleate (EM) and hydrochlorothiazide (HCT) loaded filaments were produced via hot-melt extrusion (HME). Computer software was utilized to design sets of oval bi-layer tablet of individualised doses. Thermal analysis and x-ray diffractometer (XRD) indicated that HCT remained crystalline in the polymeric matrix whilst EM appeared to be in an amorphous form. The interaction between anionic EM and cationic methacrylate polymer may have contributed to a drop in the glass transition temperature (Tg) of the filament and obviated the need for a plasticiser. Across all tablet sets, the methacrylate polymeric matrix provided immediate drug release profiles. This dynamic dosing system maintained the advantages of FDCs while providing a superior flexibility of dosing range, hence offering an optimal clinical solution to hypertension therapy in a patient-centric healthcare service. [Abstract copyright: Copyright © 2018. Published by Elsevier B.V.

Control of aggregation temperatures in mixed and blended cytocompatible thermoresponsive block co-polymer nanoparticles

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 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 mitures 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