Regioselective thioacetylation of chitosan end-groups for nanoparticle gene delivery systems

Chitosan (CS) end-group chemistry is a conjugation strategy that has been minimally exploited in the literature to date. Although the open-chain form of the CS reducing extremity bears a reactive aldehyde moiety, the most common method to generate a reactive end-group on CS is nitrous acid depolymerization, which produces a 2,5-anhydro-D-mannose unit (M-Unit) bearing also an aldehyde moiety. However, the availability of the latter might be low, since previous literature suggests that its hydrated and non-reactive form, namely the gem-diol form, is predominant in acidic aqueous conditions. Oxime-click chemistry has been used to react on such aldehydes with various degrees of success, but the use of a co-solvent and additional chemical reagents remain necessary to obtain the desired and stable covalent linkage. In this study, we have assessed the availability of the aldehyde reactive form on chitosan treated with nitrous acid. We have also assessed its reactivity towards thiol-bearing molecules in acidic conditions where CS amino groups are fully protonated and thus unreactive towards aldehyde. LC-MS and NMR spectroscopy methods (H-1 and DOSY, respectively) confirmed the regioselective thioacetylation of the reactive aldehyde with conversion rates between 55 and 70% depending on the thiol molecule engaged. The stabilization of the hemithioacetal intermediates into the corresponding thioacetals was also found to be facilitated upon freeze-drying of the reaction medium. The PEGylation of the CS M-Unit aldehyde by thioacetylation was also performed as a direct application of the proposed conjugation approach. CS-b-PEG(2) block copolymers were successfully synthesized and were used to prepare block ionomer complexes with plasmid DNA, as revealed by their spherical morphology vs. the rod-like/globular/toroidal morphology observed for polyplexes prepared using native unmodified chitosan. This novel aqueous thiol-based conjugation strategy constitutes an alternative to the oxime-click pathway; it could be applicable to other polymers

Bootstrapping Q Methodology to Improve the Understanding of Human Perspectives.

Q is a semi-qualitative methodology to identify typologies of perspectives. It is appropriate to address questions concerning diverse viewpoints, plurality of discourses, or participation processes across disciplines. Perspectives are interpreted based on rankings of a set of statements. These rankings are analysed using multivariate data reduction techniques in order to find similarities between respondents. Discussing the analytical process and looking for progress in Q methodology is becoming increasingly relevant. While its use is growing in social, health and environmental studies, the analytical process has received little attention in the last decades and it has not benefited from recent statistical and computational advances. Specifically, the standard procedure provides overall and arguably simplistic variability measures for perspectives and none of these measures are associated to individual statements, on which the interpretation is based. This paper presents an innovative approach of bootstrapping Q to obtain additional and more detailed measures of variability, which helps researchers understand better their data and the perspectives therein. This approach provides measures of variability that are specific to each statement and perspective, and additional measures that indicate the degree of certainty with which each respondent relates to each perspective. This supplementary information may add or subtract strength to particular arguments used to describe the perspectives. We illustrate and show the usefulness of this approach with an empirical example. The paper provides full details for other researchers to implement the bootstrap in Q studies with any data collection design

Exploring subjective constructions of health in China: a Q-methodological investigation

Background: With an increasing awareness of people’s satisfaction and feeling, health-related quality of life (HRQoL) has become an essential aspect of measuring health. HRQoL is fundamentally a foreign concept introduced to China from the West. While a growing number of studies applied western HRQoL measures, few content validity tests examined the legitimacy of applying Western developed HRQoL measures in a Chinese cultural setting. If there are distinct differences in health conceptualisation between China and the West, it can be argued that those western measures may fail to ask the most appropriate and important questions among a Chinese population in assessing health. As a limited number of studies have investigated Chinese people’s understandings of health, this study aimed to explore how health is defined and described in China. Methods: A Q-methodological study was conducted to explore subjective constructions of health among Chinese participants. A scoping review of Chinese generic HRQoL measures, supplemented by a series of qualitative interviews conducted in China, produced a list of 42 statements representing aspects of health considered as being important in a Chinese cultural setting. Chinese participants in face-to-face interviews ranked and sorted these statements. Data were analysed to identify clusters of participants who shared a similar perspective, using a by-person factor analysis procedure. Results: 110 Chinese participants with various demographics characteristics completed sorting interviews. Five independent factors emerged: (I) “Physical independence and social interaction skills”; (II) “Physical health”; (III) “Sensations and feelings”; (IV) “Lifestyles”; (V) “Learning and working abilities”. Conclusions: The Q-study showed that many health statements were rated highly as most important by a diverse range of Chinese participants but were not covered in the commonly used Western HRQoL measure EQ-5D. It then suggests that the EQ-5D descriptive system might need modification to improve its capacity to measure health status in China. The study thus raises a general question as to how appropriate the Western-developed HRQoL measures are when used to assess health in a significantly different cultural setting