Extrusion 3D printing of keratin protein hydrogels free of exogenous chemical agents.

Keratins are a class of intermediate filament proteins that can be obtained from numerous sources including human hair. Materials fabricated from keratins offer desirable characteristics as scaffolds for tissue engineering, including intrinsic cell adhesion sequences and tunable degradation kinetics. The capacity to create 3D printed constructs from keratin-based bio-inks generates unique opportunities for spatial control of scaffold physicochemical properties to direct scaffold functions in ways not readily achieved through other means. The aim of this study was to leverage the controllable rheological properties of keratin hydrogels to create a strategy for extrusion 3D printing of keratin bio-inks without the use of exogenous rheological modifiers, crosslinking agents, or photocurable resins. The rheological properties of keratin hydrogels were tuned by varying two parameters: (a) the ratio of keratose (obtained by oxidative extraction of keratin) to kerateine (obtained by reductive extraction of keratin); and (b) the weight percentage of total keratin protein in the gel. A computational model of the dispensing nozzle for a commercially available extrusion 3D printer was developed to calculate the needed pneumatic printing pressures based on the known rheological properties of the gels. Keratin hydrogel constructs, of varying keratose/kerateine ratios and total keratin weight percentages, were 3D printed in cylindrical geometries via extrusion 3D printing. Rheology and degradation studies showed that gels with greater relative kerateine content exhibited greater flow resistance and slower degradation kinetics when submerged in phosphate buffered saline solution at 37 °C, owing to the presence of cysteine residues in kerateine and the capability of forming disulfide bonds. Total keratin weight percentage was found to influence gel yield stress, with possible implications for tuning filament fidelity. Findings from this work support the use of keratose/kerateine ratio and total keratin weight percentage as handles for modulating rheological characteristics of keratin hydrogels to enhance printability and control scaffold properties.

Epidemiology and clinical features of emergency department patients with suspected and confirmed COVID-19: A multisite report from the COVID-19 Emergency Department Quality Improvement Project for July 2020 (COVED-3).

OBJECTIVE: The aim of the present study was to describe the epidemiology and clinical features of patients presenting to the ED with suspected and confirmed COVID-19. METHODS: The COVID-19 ED (COVED) Project is an ongoing prospective cohort study in Australian EDs. This analysis presents data from eight sites across Victoria and Tasmania for July 2020 (during Australia's 'second wave'). All adult patients who met criteria for 'suspected COVID-19' and underwent testing for SARS-CoV-2 in the ED were eligible for inclusion. Study outcomes included a positive SARS-CoV-2 test result and mechanical ventilation. RESULTS: In the period 1 July to 31 July 2020, there were 30 378 presentations to the participating EDs and 2917 (9.6%; 95% confidence interval 9.3-9.9) underwent testing for SARS-CoV-2. Of these, 50 (2%) patients returned a positive result. Among positive cases, two (4%) received mechanical ventilation during their hospital admission compared to 45 (2%) of the SARS-CoV-2 negative patients (odds ratio 1.7, 95% confidence interval 0.4-7.3; P = 0.47). Two (4%) SARS-CoV-2 positive patients died in hospital compared to 46 (2%) of the SARS-CoV-2 negative patients (odds ratio 1.7, 95% confidence interval 0.4-7.1; P = 0.49). Strong clinical predictors of a positive SARS-CoV-2 result included self-reported fever, non-smoking status, bilateral infiltrates on chest X-ray and absence of a leucocytosis on first ED blood tests (P < 0.05). CONCLUSION: In this prospective multi-site study from July 2020, a substantial proportion of ED patients required SARS-CoV-2 testing, isolation and enhanced infection prevention and control precautions. Presence of SARS-CoV-2 on nasopharyngeal swab was not associated with death or mechanical ventilation.