Microfluidic devices as gas – Ionic liquid membrane contactors for CO2 removal from anaesthesia gases

This work proposes a microfluidic gas – ionic liquid contactor for CO2 removal from anaesthesia gas, containing Xe. The working principle involves the transport of CO2 through a polymer flat membrane followed by its capture and enzymatic bioconversion in the ionic liquid solvent. Microfluidic devices enable a rapid and inexpensive screening of potential CO2 absorbers. The alveolar – type design of the ionic liquid chamber was adopted to reduce mass transfer limitations of CO2 through the liquid phase. Polydimethylsiloxane (PDMS) was the chosen polymer for dense membrane, as well as for the microfluidic device fabrication, mainly due to the high permeability of gases, O2 and CO2, and low cost. The selected ionic liquid was cholinium propionate (CP) with a water activity of 0.753, due to its high affinity towards CO2 and biocompatibility with the enzyme used for CO2 conversion to bicarbonate, carbonic anhydrase (CA). The CO2 and Xe permeability and CO2/Xe selectivity were determined in the microfluidic devices developed and compared to those exhibited by free standing PDMS membranes mounted on a standard permeation cell. The performance of the microfluidic devices as gas – ionic liquid contactors was evaluated for a given solvent flow rate with pure gas streams of CO2 and Xe. The obtained results show that cholinium propionate with or without the enzyme has no effect on the Xe transport, but remarkably enhances the affinity towards carbon dioxide leading to enhancement factor up to 1.9 in the presence of 0.1 mg CA/gIL

Protein crystallization in a microfluidic contactor with nafion®117 membranes

UIDB/50006/2020 UIDP/50006/2020 “Erasmus Mundus Doctorate in Membrane Engineering”–EUDIME (FPA 2011–2014, http://www.eudime.unical.itProtein crystallization still remains mostly an empirical science, as the production of crystals with the required quality for X-ray analysis is dependent on the intensive screening of the best protein crystallization and crystal’s derivatization conditions. Herein, this demanding step was addressed by the development of a high-throughput and low-budget microfluidic platform consisting of an ion exchange membrane (117 Nafion® membrane) sandwiched between a channel layer (stripping phase compartment) and a wells layer (feed phase compartment) forming 75 independent microcontactors. This microfluidic device allows for a simultaneous and independent screening of multiple protein crystallization and crystal derivatization conditions, using Hen EggWhite Lysozyme (HEWL) as the model protein and Hg2+ as the derivatizing agent. This microdevice offers well-regulated crystallization and subsequent crystal derivatization processes based on the controlled transport of water and ions provided by the 117 Nafion® membrane. Diffusion coefficients of water and the derivatizing agent (Hg2+) were evaluated, showing the positive influence of the protein drop volume on the number of crystals and crystal size. This microfluidic system allowed for crystals with good structural stability and high X-ray diffraction quality and, thus, it is regarded as an efficient tool that may contribute to the enhancement of the proteins’ crystals structural resolution.publishersversionpublishe

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Enhanced protein crystallization on Nafion membranes modified by low-cost Surface patterning techniques

In this work, the influence of surface topography on protein crystallization over Nafion is investigated. Two types of Nafion-based membranes were modified by soft lithographic techniques in order to create different topographies at the micro and nano scale and subsequently tested. From an analysis of the induction time, nucleation, and crystal growth rate of trypsin from bovine pancreas, all of the patterned Nafion-based membranes show an enhanced nucleation and crystal growth. To provide additional insight into the experimental observations, the wettability properties of the prepared samples and the ratio of the Gibbs free energy of heterogeneous nucleation to homogeneous nucleation were evaluated. The crystallization outcome results from the combined effect of both the structural and chemical properties of the nucleant Nafion surface.This work was supported by the Associate Laboratory for Green Chemistry-LAQV, which is financed by national funds from the FCT/MCTES (UID/QUI/50006/2019). M.P. thanks the Education, Audiovisual and Culture Executive Agency (EACEA) for a Ph.D. grant under the Program “Erasmus Mundus Doctorate in Membrane Engineering”-EUDIME (FPA 2011-2014, http://www.eudime.unical.it).Peer reviewe

Homocysteinemia as a risk factor in early cerebrovascular disease

PURPOSE: To determine whether hyperhomocysteinemia represents a risk factor of early thrombotic cerebrovascular disease. METHOD: In a group of patients under 55 years of age (n = 33, 19 males) which had suffered a stroke from 3 months to 1 year before the study, defined by clinical criteria and presence of cerebral infarction confirmed by tomography, without history or predisposition to embolic disease. The patients were matched with a group of normal controls of checkup program, in terms of age, and sex. Patients and controls with a history of alcoholism, clinical or laboratory signs of renal or hepatic insufficiency or with a history of recent ingestion of Group B vitamins were excluded since these conditions would influence homocysteinemia levels. We measured the plasmatic basal homocysteinemia of patients and controls (HC) and 6 hours later a methionine overload of 0.1 g/Kg body weight (LOAD HC). RESULTS: Patients; Controls; Signific.; Age 46.0 +/- 7.7; 45.9 +/- 7.8; NS; Basal HC. 10.1 +/- 3.4; 8.5 +/- 1.7; p < 0.05; Load HC 28.0 +/- 7.6; 22.7 +/- 5.5; p < 0.01. CONCLUSION: In this study hyperhomocysteinemia appears as a risk factor for thrombotic cerebrovascular disease before the age of 55;-The measurement of homocysteinemia after the methionine loading test was more discriminative than the basal measurement;-A larger number of patients and controls will be necessary to establish the relative importance of homocysteinemia among other vascular risk factors in cerebrovascular disease.publishersversionpublishe