Assembly of Nucleic Acid-Based Nanoparticles by Gas-Liquid Segmented Flow Microfluidics

The development of novel and efficient mixing methods is important for optimizing the efficiency of many biological and chemical processes. Tuning the physical and performance properties of nucleic acid-based nanoparticles is one such example known to be strongly affected by mixing efficiency. The characteristics of DNA nanoparticles (such as size, polydispersity, ζ-potential, and gel shift) are important to ensure their therapeutic potency, and new methods to optimize these characteristics are of significant importance to achieve the highest efficacy. In the present study, a simple segmented flow microfluidics system has been developed to augment mixing of pDNA/bPEI nanoparticles. This DNA and cationic polymer pair (plasmid DNA and branched poly(ethylenimine)) was chosen due to bPEI’s well-known ability to spontaneously condense plasmid DNA. The system fabricated in this project utilizes silastic tubing (1.6 mm ID) as the reaction channels, nitrogen gas as the continuous phase, and the aqueous components as the dispersed phase. Drop flow has been characterized using UV/Vis spectrophotometry, and the relationships between continuous and dispersed phase flow and drop rate and size have been documented. Drops have been successfully formed using two different types of drop generation (cross-flow and co-flow). Physical properties of the nanoparticles were analyzed using dynamic light scattering (DLS) measurements and agarose gel electrophoresis. Biological performance of the nanoparticles was analyzed using DNase I protection, unincorporated bPEI quantitation, mammalian cell transfection, and cell viability assays. The nitrogen-to-phosphate (N/P) ratio (5 and 20), flow rate, and flow-path geometry (linear, serpentine, and coiled) have been explored for their effect on mixing and particle uniformity. The results show a significant decrease in nanoparticle size compared with bulk-mixed methods at an N/P ratio of 5 and an observable difference in nanoparticle properties and performance when adjusting the nature of mixing using the developed microfluidics system

Increasing frailty is associated with higher prevalence and reduced recognition of delirium in older hospitalised inpatients: results of a multi-centre study

Purpose: Delirium is a neuropsychiatric disorder delineated by an acute change in cognition, attention, and consciousness. It is common, particularly in older adults, but poorly recognised. Frailty is the accumulation of deficits conferring an increased risk of adverse outcomes. We set out to determine how severity of frailty, as measured using the CFS, affected delirium rates, and recognition in hospitalised older people in the United Kingdom. Methods: Adults over 65 years were included in an observational multi-centre audit across UK hospitals, two prospective rounds, and one retrospective note review. Clinical Frailty Scale (CFS), delirium status, and 30-day outcomes were recorded. Results: The overall prevalence of delirium was 16.3% (483). Patients with delirium were more frail than patients without delirium (median CFS 6 vs 4). The risk of delirium was greater with increasing frailty [OR 2.9 (1.8–4.6) in CFS 4 vs 1–3; OR 12.4 (6.2–24.5) in CFS 8 vs 1–3]. Higher CFS was associated with reduced recognition of delirium (OR of 0.7 (0.3–1.9) in CFS 4 compared to 0.2 (0.1–0.7) in CFS 8). These risks were both independent of age and dementia. Conclusion: We have demonstrated an incremental increase in risk of delirium with increasing frailty. This has important clinical implications, suggesting that frailty may provide a more nuanced measure of vulnerability to delirium and poor outcomes. However, the most frail patients are least likely to have their delirium diagnosed and there is a significant lack of research into the underlying pathophysiology of both of these common geriatric syndromes

Determining the concentration of CuInS2 quantum dots from the size-dependent molar extinction coefficient

The size-dependent nature of the molar extinction coefficient of highly photoluminescent copper indium sulfide (CuInS2) quantum dots (CIS-QDs) is presented. We determined the extinction coefficients at both high photon energy (3.1 eV) and at the first excitonic transition band for CIS-QDs, ranging in size from 2.5 nm to 5.1 nm. Both coefficient trends displayed a power-law size dependence for the QDs. These data allow the in situ assessment of the CIS-QD concentration via routine optical absorption measurements, which is an important parameter for many applications. The formation of ZnS on the surface of CIS-QDs dramatically increases the photoluminescence quantum yield, while also blue-shifting the photoluminescent emission. Importantly, we conclude that the concentration of core/shell CIS/ZnS-QD dispersions can be determined using the molar extinction coefficient data of core CIS-QDs. The experimental uncertainties in the solution concentrations determined from the molar extinction coefficient data are in the range of 10%–15%