Size‐Dependent Photocatalytic Reactivity of Conjugated Microporous Polymer Nanoparticles

Particle size is a critical factor for improving photocatalytic reactivity of conjugated microporous polymers (CMPs) as mass transfer in the porous materials is often the rate‐limiting step. However, due to the synthetic challenge of controlling the size of CMPs, the impact of particle size is yet to be investigated. To address this problem, a simple and versatile dispersion polymerization route that can synthesize dispersible CMP nanoparticles with controlled size from 15 to 180 nm is proposed. Leveraging the precise control of the size, it is demonstrated that smaller CMP nanoparticles have dramatically higher photocatalytic reactivity in various organic transformations, achieving more than 1000% enhancement in the reaction rates by decreasing the size from 180 to 15 nm. The size‐dependent photocatalytic reactivity is further scrutinized using a kinetic model and transient absorption spectroscopy, revealing that only the initial 5 nm‐thick surface layer of CMP nanoparticles is involved in the photocatalytic reactions because of internal mass transfer limitations. This finding substantiates the potential of small CMP nanoparticles to efficiently use photo‐generated excitons and improve energy‐efficiency of numerous photocatalytic reactions

Evaluation of Nanoparticles Covalently Bound with BODIPY for Their Photodynamic Therapy Applicability

Photodynamic therapy (PDT) relies on the combined action of a photosensitizer (PS), light at an appropriate wavelength, and oxygen, to produce reactive oxygen species (ROS) that lead to cell death. However, this therapeutic modality presents some limitations, such as the poor water solubility of PSs and their limited selectivity. To overcome these problems, research has exploited nanoparticles (NPs). This project aimed to synthesize a PS, belonging to the BODIPY family, covalently link it to two NPs that differ in their lipophilic character, and then evaluate their photodynamic activity on SKOV3 and MCF7 tumor cell lines. Physicochemical analyses demonstrated that both NPs are suitable for PDT, as they are resistant to photobleaching and have good singlet oxygen (1O2) production. In vitro biological analyses showed that BODIPY has greater photodynamic activity in the free form than its NP-bounded counterpart, probably due to greater cellular uptake. To evaluate the main mechanisms involved in PDT-induced cell death, flow cytometric analyses were performed and showed that free BODIPY mainly induced necrosis, while once bound to NP, it seemed to prefer apoptosis. A scratch wound healing test indicated that all compounds partially inhibited cellular migration of SKOV3 cells

Neck muscle cross-sectional area, brain volume and cognition in healthy older men; A cohort study

BACKGROUND: Two important consequences of the normal ageing process are sarcopenia (the age-related loss of muscle mass and function) and age-related cognitive decline. Existing data support positive relationships between muscle function, cognition and brain structure. However, studies investigating these relationships at older ages are lacking and rarely include a measure of muscle size. Here we test whether neck muscle size is positively associated with cognition and brain structure in older men. METHODS: We studied 51 healthy older men with mean age 73.8 (sd 1.5) years. Neck muscle cross-sectional area (CSA) was measured from T1-weighted MR-brain scans using a validated technique. We measured multiple cognitive domains including verbal and visuospatial memory, executive functioning and estimated prior cognitive ability. Whole brain, ventricular, hippocampal and cerebellar volumes were measured with MRI. General linear models (ANCOVA) were performed. RESULTS: Larger neck muscle CSA was associated with less whole brain atrophy (t = 2.86, p = 0.01, partial eta squared 17%). Neck muscle CSA was not associated with other neuroimaging variables or current cognitive ability. Smaller neck muscle CSA was unexpectedly associated with higher prior cognition (t = −2.12, p < 0.05, partial eta squared 10%). CONCLUSIONS: In healthy older men, preservation of whole brain volume (i.e. less atrophy) is associated with larger muscle size. Longitudinal ageing studies are now required to investigate these relationships further

Data associated with 'pH-responsive polymer microcapsules for targeted delivery of biomaterials to the midgut of Drosophila suzukii'

Drosophila suzukii (or spotted wing Drosophila) is an economically important pest which can have a devastating impact on soft and stone fruit industries. Biological pesticides are being sought as alternatives to synthetic chemicals to control this invasive pest, but many are subject to degradation either in the environment or in the insect gut and as a result require protection. In this study we identified a sharp change in pH of the adult midgut from neutral to acidic (pH 6, but underwent rapid dissolution at pH < 4.2. In vivo studies showed that the natural acidity of the midgut of D. suzukii also induced the breakdown of the responsive P2VP microcapsules to release FITC-dextran which was taken up into the body of the insect and accumulated in the renal tubules

Therapeutic applications of responsive organic photocatalytic polymers, enabling <i>in situ </i>drug activation †

Targeted prodrug activation within the acidic tumour microenvironment is needed to limit off-target effects in chemotherapy. This in combination with photodynamic generation of reactive oxygen species (ROS) can be used for efficient remediation of cancerous tissue. To achieve this, pH-responsive polymers with photocatalytic units that become activated in the acidic pH of the tumour microenvironment have been created. Four model prodrug linkages in small molecule substrates have been investigated along with a model polymer-based prodrug. We have demonstrated the pH-dependent activation of model prodrug molecules, due to conformational changes of the pH-responsive photocatalytic polymers. Additionally, a prodrug of the common skin cancer chemotherapy drug 5-fluorouracil (5FU) could be photocatalytically activated and could induce cell death in cancer cells

Tunable Photocatalytic Selectivity by Altering the Active Center Microenvironment of an Organic Polymer Photocatalyst

The favored production of one product over another is a major challenge in synthetic chemistry, reducing the formation of byproducts and enhancing atom efficacy. The formation of catalytic species that have differing reactivities based on the substrate being converted, has been targeted to selectively control reactions. Here, we report the production of photocatalytic self-assembled amphiphilic polymers, with either hydrophilic or hydrophobic microenvironments at the reactive center. Benzothiadiazole-based photocatalysts were polymerized into either the hydrophilic or the hydrophobic compartment of a diblock copolymer by RAFT polymerization. The difference in the reactivity of each microenvironment was dictated by the physical properties of the substrate. Stark differences in reactivity were observed for polar substrates, where a hydrophilic microenvironment was favored. Conversely, both microenvironments performed similarly for very hydrophobic substrates, showing that reagent partitioning is not the only factor that drives photocatalytic conversion. Furthermore, the use of secondary swelling solvents allowed an additional reagent exchange between the continuous phase and the heterogeneous photocatalyst, resulting in a significant 5-fold increase in conversion for a radical carbon–carbon coupling

In vitro release of FITC-dextran from responsive microcapsules in different pH buffers.

<p>P2VP pH-responsive microcapsules in a pH 6 (n = 4) environment showed no release of encapsulated FITC-dextran over 24 h as the pH was above the pKa of the microcapsules. At the lower pH of 3.8 (n = 4) around 80% of the encapsulated FITC-dextran was released within the first 5 mins, no further release was observed after this time. It is assumed that the unaccounted 20% is lost during the production of the microcapsules.</p

Polymerised multiple emulsion template yielding solid P2VP microcapsules.

<p>(<b>a-d</b>) Optical microscopy of microcapsules formed from polymerisation of the oil phase of the multiple emulsion template. (<b>e</b>) SEM analysis of the loaded microcapsules (<b>f</b>) Size measurement using light scattering, average distribution expressed as volume (%) (n = 10), of the microcapsules ranging from 2–100 <b>μ</b>m. The smaller peak around 1 <b>μ</b>m is a by-product formed of solid polymer particles containing no active species.</p