Synthesis and characterisation of biocompatible organic-inorganic core-shell nanocomposite particles based on ureasils.

Organic-inorganic core-shell nanocomposites have attracted increasing attention for applications in imaging, controlled release, biomedical scaffolds and self-healing materials. While tunable properties can readily be achieved through the selection of complementary building blocks, synergistic enhancement requires management of the core-shell interface. In this work, we report a one-pot method to fabricate hybrid core-shell nanocomposite particles (CSNPs) based on ureasils. The native structure of ureasils, which are poly(oxyalkylene)/siloxane hybrids, affords formation of an organic polymer core via nanoprecipitation, while the terminal siloxane groups act as a template for nucleation and growth of the silica shell via the Stöber process. Through optimisation of the reaction conditions, we demonstrate the reproducible synthesis of ureasil CSNPs, with a hydrodynamic diameter of ∼150 nm and polydispersity 50 days. Selective functionalisation, either through the physical entrapment of polarity-sensitive fluorescent probes (coumarin 153, pyrene) or covalent-grafting to the silica shell (fluorescein isothiocyanate) is also demonstrated and provides insight into the internal environment of the particles. Moreover, preliminary studies using a live/dead cell assay indicate that ureasil CSNPs do not display cytotoxicity. Given the simple fabrication method and the structural tunability and biocompatability of the ureasils, this approach presents an efficient route to multifunctional core-shell nanocomposite particles whose properties may be tailored for a targeted application

Luminescent Solar Concentrators Based on Energy Transfer from an Aggregation-Induced Emitter Conjugated Polymer.

Luminescent solar concentrators (LSCs) are solar-harvesting devices fabricated from a transparent waveguide that is doped or coated with lumophores. Despite their potential for architectural integration, the optical efficiency of LSCs is often limited by incomplete harvesting of solar radiation and aggregation-caused quenching (ACQ) of lumophores in the solid state. Here, we demonstrate a multilumophore LSC design that circumvents these challenges through a combination of nonradiative Förster resonance energy transfer (FRET) and aggregation-induced emission (AIE). The LSC incorporates a green-emitting poly(tetraphenylethylene), p-O-TPE, as an energy donor and a red-emitting perylene bisimide molecular dye (PDI-Sil) as the energy acceptor, within an organic-inorganic hybrid diureasil waveguide. Steady-state photoluminescence studies demonstrate the diureasil host induced AIE from the p-O-PTE donor polymer, leading to a high photoluminescence quantum yield (PLQY) of ∼45% and a large Stokes shift of ∼150 nm. Covalent grafting of the PDI-Sil acceptor to the siliceous domains of the diureasil waveguide also inhibits nonradiative losses by preventing molecular aggregation. Due to the excellent spectral overlap, FRET was shown to occur from p-O-TPE to PDI-Sil, which increased with acceptor concentration. As a result, the final LSC (4.5 cm × 4.5 cm × 0.3 cm) with an optimized donor-acceptor ratio (1:1 by wt %) exhibited an internal photon efficiency of 20%, demonstrating a viable design for LSCs utilizing an AIE-based FRET approach to improve the solar-harvesting performance

Ureasil Architectures for Organic-Inorganic Photoactive Hybrid Materials

Ureasils are Class II organic-inorganic hybrids consisting of poly(oxyalkylene) chains covalently linked to a siliceous network via urea bridges. Ureasil monoliths are photoluminescent, waveguiding and photo- and thermally stable and have been used as hosts for emissive species such as lanthanides, organic dyes and conjugated polymers (CPs). CPs and conjugated organic dyes in particular, are promising materials for flexible lightweight devices such as organic light-emitting diodes and luminescent solar concentrators (LSCs). However, their solid-state morphology can significantly influence their optoelectronic properties, leading to the need for sophisticated design methodologies when trying and incorporate them into devices. To meet this challenge, this work begins with an investigation of different incorporation strategies for π-conjugated fluorophores into ureasils. Firstly, a siloxane-functionalised poly(fluorene) (PF) (Chapter 3) and a perylene dicarboxdiimide (PDI) (Chapter 4) were covalently grafted via co-condensation to the ureasil siliceous backbone, to achieve their selective localisation within the ureasil matrix. The degree of branching and the molecular weight of the poly(oxyalkylene) backbone were also probed. In both cases, covalent grafting influenced the optical properties of the resultant material; in PF-ureasils, it results in controlled packing of the PF chains, which promotes the formation of the π-stacked β-phase, typical for PFs, which has been linked to enhanced optoelectronic properties. For PDI dyes, covalent-grafting inhibits aggregation and minimises re-absorption losses in PDI-ureasils. Moreover, the ureasil behaves as a donor for energy transfer (ET) to the PDI, enabling tuning of the emission colour. In Chapter 5, a poly(fluorene-alt-phenylene) (PBS-PFP) copolymer containing on-chain PDI units was physically dispersed in ureasil matrices. The possibility of ET between the ureasil and/or the PBS-PFP donors to the PDI acceptor was investigated. Lifetime measurements showed that good spectral overlap, combined with efficient electronic coupling results in excitation ET from the ureasil to the PBS-PFP units. This process however, inhibits subsequent ET to the PDI chromophore, but leads to high photoluminescence quantum yields (>50%). Due to the low on chain PDI/PBS-PFP ratio, the performance of the system as an LSC is mediocre, but can be boosted by further doping with PDI using a model system. These results demonstrate that the use of an active waveguide host is a promising step towards design of next generation LSCs. Finally, in Chapter 6, a new ureasil architecture is presented, through the development of hybrid nanoparticles (NPs) consisting of a ureasil core and a silica shell. Upon optimisation of the synthesis, NPs with size of ~200 nm and a polydispersity index of ~0.2, were obtained and remained stable for over 50 days. Incorporation of organic fluorophores within the NPs was investigated by: (i) a non-covalent approach, where dyes are encapsulated in the NPs and (ii) a covalent approach, where the dye is covalently grafted the NPs siliceous backbone. These examples demonstrate that the simplicity and the versatility of the sol-gel process offer a wide range of possibilities for targeted design of fluorophore-integrated ureasil hybrids. This platform enables us to obtain a variety of hybrid architectures capable of incorporating both CPs and organic dyes, with the possibility of targeting some optoelectronic properties and/or to improve their photo- and their thermal stability, for application in both solid-state emitting devices and dye-doped NPs for imaging

Research data supporting "Targeted β-phase formation in poly(fluorene)-ureasil grafted organic-inorganic hybrids"

The folder “Figure 2” contains data for the 1H NMR spectra of PF-PTES (3), ICPTES (2) and PFO-OH (1), recorded in CDCl3, using 400 MHz. The folder “Figure 3” contains data for FTIR spectrum and gaussian curve fitting results of the amide I region of DU-PF-0.01, to quantitively analyse the hydrogen-bonding structure in the ureasil hybrids. The folder “Figure 4” contains data for 29Si MAS NMR spectra recorded for DU-PF-0.05, DU-PF-0, TU-PF-0.05 and TU-PF-0, using cross-polarised (CP) and directly excited (DE) magic angle spinning (MAS) solid-state NMR spectrum, operating at 79.44 MHz. The folder “Figure 5” contains the data for absorption, excitation, and emission spectra of PFO-OH in THF solution, DU-PF-0.01 and TU-PF-0.01. The excitation and emission spectra of PFO-OH in THF solution were recorded with emission and excitation wavelength of 480 and 350 nm, respectively. The excitation and emission spectra of DU-PF-0.01 and TU-PF-0.01 were recorded with emission and excitation wavelength of 500 and 360 nm, respectively. The folder “Figure 6” contains data for (a) emission (λex = 360 nm) and (b) excitation (b, λem = 500 nm) spectra of DU-PF-0.01 recorded as a function of time after the initiation of the sol-gel reaction (t = 0 to 143 h). The folder “Figure 7” contains data for (a) area-normalised excitation spectrum of DU-PF-0.01 (λem = 480 nm) and the corresponding Gaussian fits of the spectral components associated with the vibronic modes of PFO-OH and (b) %β-contribution and photoluminescence quantum yields as a function of the PFO-OH wt% for the DU-PF-x and TU-PF-x sample series. The folder “Figure S1” contains the data for the thermograms of ICPTES, PFO and PF-PTES. The data was recorded at air atmosphere, with heat rate = 10 oC min-1. The folder “Figure S2” contains the data for the FTIR spectra of (a) ICPTES, Jeffamine ED-600 and d-UPTES and (b) ICPTES, Jeffamine T-403 and t-UPTES. The FTIR spectra were recorded at a resolution of 4 cm-1, over a range of 4000-650 cm-1 to monitor the completion of the coupling between ICPTES and Jeffamine during the first step of the sol-gel reaction. The folder “Figure S3” contains the data for the FTIR spectra and Gaussian curve-fittings for the Amide I region of (a) DU-PF-0 (b) DU-PF-0.05 (c) DU-PF-0.1 (d) TU-PF-0 (e) TU-PF-0.01 (f) TU-PF-0.05 and (g) TU-PF-0.1. The data are used to quantitively analyse the hydrogen bonding structure of the ureasil hybrids. The folder “Figure S4” contains the data for the 13C NMR spectra of (a) TU-PF-0.05, (b) TU-PF-0, (c) DU-PF-0.05 and (d) DU-PF-0, recorded with cross-polarised (CP) magic angle spinning (MAS) solid state NMR, with 100.56 MHz. The folder “Figure S5” contains the data for powder X-ray diffraction measurements for (a) DU-PF-x and (b) TU-PF-x samples, where x stands for the concentration of the conjugated polymer in the ureasil matrixes. The folder “Figure S6” contains the data for the thermograms of (a) DU-PF-0, DU-PF-0.01, DU-PF-0.05 and DU-PF-0.1 and (b) TU-PF-0, TU-PF-0.01. TU-PF-0.05 and TU-PF-0.1, measured in air atmosphere, with heating rate of 10 oC min-1. The folder “Figure S7” contains the data for the emission spectra of (a) DU-PF-0.01, (b) DU-PF-0.05, (c) DU-PF-0.1, (d) TU-PF-0.01 (e) TU-PF-0.05 and (f) TU-PF-0.1 as a function of excitation wavelengths (320, 330 and 340 nm). The folder “Figure S8” contains the data for the excitation spectra of (a) DU-PF-0.01, (b) DU-PF-0.05, (c) DU-PF-0.1, (d) TU-PF-0.01 (e) TU-PF-0.05 and (f) TU-PF-0.1 as a function of emission wavelengths (430, 440, 460, 470, 500 and 520 nm). The folder “Figure S9” contains the data for the area-normalised excitation spectrum of PFO-OF (10-6 mol × dm-3, λem = 480 nm) and the corresponding Gaussian-fits of the spectral components associated with the 0-0, 0-1, 0-2, 0-3 vibronic transition of PFO-OH and the blue and purplish components of the ureasil. The folder “Figure S10” contains the data for the excitation spectra (λem = 480 nm) of (a) DU-PF-0.05, (b) DU-PF-0.05 and (d) TU-PF-0.1 and the corresponding Gaussian-fits of the spectral components 0-0, 0-1, 0-2, 0-3 and the ureasil blue and purplish components

Luminescent Solar Concentrators Based on Energy Transfer from an Aggregation-Induced Emitter Conjugated Polymer

Luminescent solar concentrators (LSCs) are solar-harvesting devices fabricated from transparent waveguide that is doped or coated with lumophores. Despite their potential for architectural integration, the optical efficiency of LSCs is often limited by incomplete harvesting of solar radiation and aggregation-caused quenching (ACQ) of lumophores in the solid state. Here, we demonstrate a multi-lumophore LSC design which circumvents these challenges through a combination of non-radiative Förster energy transfer (FRET) and aggregation-induced emission (AIE). The LSC incorporates a green-emitting poly(tetraphenylethylene), p-O-TPE, as an energy donor and a red-emitting perylene bisimide molecular dye (PDI-Sil) as the energy acceptor, within an organic-inorganic hybrid di-ureasil waveguide. Steady-state photoluminescence studies demonstrate that the di-ureasil host induced AIE from the p-O-PTE donor polymer, leading to a high photoluminescence quantum yield (PLQY) of ~45% and a large Stokes shift of ~150 nm. Covalent grafting of the PDI-Sil acceptor to the siliceous domains of the di-ureasil waveguide also inhibits non-radiative losses by preventing molecular aggregation. Due to the excellent spectral overlap, FRET was shown to occur from p-O-TPE to PDI-Sil, which increased with acceptor concentration. As a result, the final LSC (4.5 cm x 4.5 cm x 0.3 cm) with an optimised donor- acceptor ratio (1:1 by wt%) exhibited an internal photon efficiency of 20%, demonstrating a viable design for LSCs utilising an AIE-based FRET approach to improve the solar-harvesting performance.</div

Research data supporting "Synthesis and Characterisation of Biocompatible Organic- Inorganic Core-Shell Nanocomposite Particles based on Ureasils"

The folder “figure 3” contains dynamic light scattering data for CSNP’s made using method B showing the evolution of the hydrodynamic diameter, polydispersity and PDI as a function of time. The data points are an average of three values obtained for the samples. The folder “figure 4” contains tapping-mode AFM images of the CSNPs. (1,3) and (2,4) represent the same scale. (1,2) are height contrast images, whereas (3,4) are phase contrast images. The folder “figure 5” contains dynamic light scattering data for CSNPs made using method C (TEOS addition rate 60 µL/60mins and 10mM NH4OH solution) showing hydrodynamic diameter and polydispersity. The folder “figure 6” contains emission spectra for (a) Py@CSNPs and Py in water and ethanol (2.5x10-5 mol L-1) with (ex = 335nm), (c) C154 and C153@CSNPs after dialysis with (ex = 420 nm), (d) FITC@CSNPs before and after dialysis (ex = 465 nm). Also included is (b) I3/I1 ratio for Py@CSNPs over time and normalized intensity of the emission maximum of the excimer emission. The folder “figure 7” contains fluorescence microscopy images of a live/dead cell assay of HEK293 cells exposed to ureasil CSNPS for concentrations 0.001-1 mg/ml for 24 h. The folder “figure S2” contains dynamic light scattering data for CSNPs made using method A. Samples were prepared on different days. A correlogram and size distribution are given. The folder “figure S3” contains data showing the change in hydrodynamic diameter and polydispersity, recorder for CSNP’s mad using method A, with respect to time. Measurements were made using dynamic light scattering. The folder “figure S5” contains dynamic light scattering data showing the change in nanoparticle size and polydispersity for CSNPs prepared using method C. Samples differ by base concentration and TEOS addition rate. The folder “figure S6” contains I3/I1 fluorescence intensity ratios for pyrene in water/ethanol mixtures at different volume percentage of water (dye conc. = 2.5 × 10-5 mol L-1). λex = 335 nm. The folder “figure S7” contains normalized absorption, emission (λex = 420 nm) and excitation (λem = 550 nm) spectra of C153 in water and upon incorporation into CSNPs. (dye conc. = 3.6 × 10-5 mol L-1). The folder “figure S8” contains dynamic light scattering data showing the change in nanoparticle size and polydispersity for APTES and FTIC doped CSNPs. The folder “figure S9” contains time-resolved fluorescence data for FNa and FITC@CSNPs before and after dialysis. Also given are data fits with weighted residuals and instrument response functions

3D printed mucoadhesive orodispersible films manufactured by direct powder extrusion for personalized clobetasol propionate based paediatric therapies

The aim of this work is the development and production by Direct Powder Extrusion (DPE) 3D printing technique of novel oral mucoadhesive films delivering Clobetasol propionate (CBS), useful in paediatric treatment of Oral Lichen Planus (OLP), a rare chronic disease. The DPE 3D printing of these dosage forms can allow the reduction of frequency regimen, the therapy personalization, and reduction of oral cavity administration discomfort. To obtain suitable mucoadhesive films, different polymeric materials, namely hydroxypropylmethylcellulose or polyethylene oxide blended with chitosan (CS), were tested and hydroxypropyl-&amp; beta;-cyclodextrin was added to increase the CBS solubility. The formulations were tested in terms of mechanical, physico-chemical, and in vitro biopharmaceutical properties. The film showed a tenacious structure, with drug chemical-physical characteristics enhancement due to its partial amorphization during the printing stage and owing to cyclodextrins multicom-ponent complex formation. The presence of CS enhanced the mucoadhesive properties leading to a significant increase of drug exposure time on the mucosa. Finally, the printed films permeation and retention studies through porcine mucosae showed a marked retention of the drug inside the epithelium, avoiding drug systemic absorption. Therefore, DPE-printed films could represent a suitable technique for the preparation of mucoad-hesive film potentially usable for paediatric therapy including OLP