Design of melt-recyclable poly(ε-caprolactone)-based supramolecular shape-memory nanocomposites

A novel poly(epsilon-caprolactone) (PCL) supramolecular network exhibiting shape-memory behavior was successfully constructed with pendant UPy units that are highly able to dimerize. The dynamic network was obtained by a simple and versatile strategy consisting of chain-extension reaction between α,ω-dihydroxyoligoPCL and hydroxylated UPy units in the presence of hexamethylene diisocyanate as a coupling agent and further intermolecular dimerization of the UPy along the polyurethane backbone. ¹H NMR analyses confirmed the dynamic features of the system, and DMTA in tensile mode was investigated to assess the SMP properties. Recyclability was also assessed by taking advantage of these supramolecular networks. Further addition of cellulose nanocrystals into the polymer network enabled adjustment of the extent of the net-points and therefore the SMP features. As confirmed by dispersion tests in solution and SEM observations, these bio-based nanofillers were homogeneously distributed in the network via supramolecular interaction between the hydroxyl groups present on their surface and UPy moieties along the polyurethane backbone. Thus, the here developed nanomaterials might reveal applicability in areas where a combination of SMP and biocompatibility is needed.

Novel melt-recyclable poly(ε-caprolactone)/cellulose nanocrystals supramolecular nanocomposite networks with shape-memory behavior have been successfully constructed by playing with UPy chemistry.     

The influence of small field output factors simulated uncertainties on the calculated dose in VMAT plans for brain metastases: a multicentre study

Objectives:This multicentric study was carried out to investigate the impact of small field output factors (OFs) inaccuracies on the calculated dose in volumetric arctherapy (VMAT) radiosurgery brain plans.Methods:Nine centres, realised the same five VMAT plans with common planning rules and their specific clinical equipment Linac/treatment planning system commissioned with their OFs measured values (OFbaseline). In order to simulate OFs errors, two new OFs sets were generated for each centre by changing only the OFs values of the smallest field sizes (from 3.2 × 3.2 cm² to 1 × 1 cm²) with well-defined amounts (positive and negative). Consequently, two virtual machines for each centre were recommissioned using the new OFs and the percentage dose differences ΔD (%) between the baseline plans and the same plans recalculated using the incremented (OFup) and decremented (OFdown) values were evaluated. The ΔD (%) were analysed in terms of planning target volume (PTV) coverage and organs at risk (OARs) sparing at selected dose/volume points.Results:The plans recalculated with OFdown sets resulted in higher variation of doses than baseline within 1.6 and 3.4% to PTVs and OARs respectively; while the plans with OFup sets resulted in lower variation within 1.3% to both PTVs and OARs. Our analysis highlights that OFs variations affect calculated dose depending on the algorithm and on the delivery mode (field jaw/MLC‐defined). The Monte Carlo (MC) algorithm resulted significantly more sensitive to OFs variations than all of the other algorithms.Conclusion:The aim of our study was to evaluate how small fields OFs inaccuracies can affect the dose calculation in VMAT brain radiosurgery treatments plans. It was observed that simulated OFs errors, return dosimetric calculation accuracies within the 3% between concurrent plans analysed in terms of percentage dose differences at selected dose/volume points of the PTV coverage and OARs sparing.Advances in knowledge:First multicentre study involving different Planning/Linacs about undetectable errors in commissioning output factor for small fields.     

One‐step radiosynthesis of [18F]LBT‐999: a selective radioligand for the visualization of the dopamine transporter with PET

LBT‐999 (8‐((E)‐4‐fluoro‐but‐2‐enyl)‐3‐beta‐p‐tolyl‐8‐aza‐bicyclo[3.2.1]octane‐2‐beta‐carboxylicacid methyl ester) is a recently developed cocaine derivative belonging to a new generation of highly selective dopamine transporter (DAT) ligands (K_D : 9 nM for the DAT and IC₅₀ > 1000 nM for the serotonin and norepinephrine transporter). Initial fluorine‐18‐labelling of LBT‐999 was based on the robust and reliable two‐step radiochemical pathway often reported for such tropane derivatives, involving first the preparation of (E)‐1‐[¹⁸F]fluoro‐4‐tosyloxybut‐2‐ene followed by a N‐alkylation reaction with the appropriate nor‐tropane moiety. In the present work, a simple one‐step fluorine‐18‐labelling of LBT‐999 is reported, based on a chlorine‐for‐fluorine nucleophilic aliphatic substitution, facilitating as expected both automation and final high‐performance liquid chromatography (HPLC) purification. The process involves: (A) reaction of K[¹⁸F]F–Kryptofix^®222 with the chlorinated precursor (3.5–4.5 mg) at 165°C for 10 min in DMSO (0.6 mL) followed by (B) C‐18 PrepSep cartridge pre‐purification and finally (C) semi‐preparative HPLC purification on a Waters Symmetry^® C‐18. Typically, 3.70–5.92 GBq of [¹⁸F]LBT‐999 (> 95% chemically and radiochemically pure) could be obtained with specific radioactivities ranging from 37 to 111 GBq/µmol within 85–90 min (HPLC purification and Sep‐Pak‐based formulation included), starting from a 37.0 GBq [¹⁸F]fluoride batch (overall radiochemical yields: 10–16%, non‐decay‐corrected). Copyright © 2007 John Wiley & Sons, Ltd.     

Tricks and pitfalls regarding the hemodynamics of patients undergoing non-transplantation surgery for heart failure

This paper aims to address the mechanisms responsible for poor perioperative cardiac performance, analyzing the pathophysiology of heart failure and the main hemodynamic parameters (contractility, preload, afterload, systemic vascular resistance, and pulmonary artery pressure) used in diagnosing patients and assessing their response to therapy. It will also discuss potential therapeutic approaches to cardiac surgery patients. With advances in monitoring and life support, our critically ill patients often become trapped in a sheer, impenetrable net of wires and tubes. Unfortunately, technology can seriously compromise patient safety if the data obtained is misinterpreted. While advanced technology has become a part of daily life in the Intensive Care Unit (ICU), there remains a crucial step that cannot be performed by computers: the link from sensors to patient status. We should always remember to look past the cables and monitors and to look at the patient. This would not only reduce the number of ever-present wires, but would also help improve patient outcome. The field of non-transplant cardiac surgery for heart failure is extremely challenging for the cardiac anesthesiologist. The high incidence of postoperative low cardiac output syndrome should mandate aggressive monitoring and therapy. Nevertheless, a comprehensive understanding of the pathophysiology of heart failure and the hemodynamic implications of surgical therapies is mandatory for optimal patient management. In particular, the presence of systolic dysfunction should not automatically rule out other potential causes of poor global cardiac performance.     

LIPID‐LOWERING THERAPY IN CHRONIC KIDNEY DISEASE: IS THERE A ROLE FOR EZETIMIBE?

The use of lipid-lowering therapy (LLT) in chronic kidney disease (CKD) results in a reduction in atherosclerotic cardiovascular events but not mortality. The risk reduction for patients on dialysis appears to be less than in pre-dialysis CKD. These findings may be due to the higher rate of non-atherosclerotic cardiovascular disease found in end-stage disease. Because of this, the role of LLT is less clear in CKD than in the general population. This review outlines the results of recent trials of LLT, particularly Ezetimibe, and implications for patients with CKD. The evidence in favour of lipid lowering in CKD comes largely from the SHARP study. This study used combined simvastatin and Ezetimibe to reduce cholesterol. Though the benefits of statins are well proven, there is no evidence that Ezetimibe independently reduces cardiovascular events in any population. Data which support the use of Ezetimibe show only that it effectively reduces cholesterol. Surrogate end-point data are contentious. Some studies suggest benefit whilst others suggest off-target effects that question the validity of Ezetimibe in the absence of quality cardiovascular outcome data.     

Temperature management during off-pump coronary artery bypass graft surgery: a randomized clinical trial on the efficacy of a circulating water system versus a forced-air system

OBJECTIVE: The aim of this study was to evaluate the performance of a new temperature management system specifically designed for cardiac surgery (Allon ThermoWrapping Thermoregulation System; MTRE Advanced Technologies Ltd, Or Akiva, Israel) using a circulating-water garment and to compare it with a conventional forced-air cover system in order to determine whether it could reduce the incidence of perioperative hypothermia during off-pump coronary artery bypass graft (OPCAB) surgery. DESIGN: Prospective, randomized. SETTING: University, tertiary care hospital. PARTICIPANTS: Thirty-one patients undergoing primary OPCAB surgery. INTERVENTIONS: Patients undergoing OPCAB surgery were randomized into the new thermoregulation system, Allon (study group, n = 15), and the standard forced-air system, Bair Hugger (Sterile Cardiac Access blanket Model 645; Augustine SA, Berne, Switzerland) (control group, n = 16). MEASUREMENTS AND MAIN RESULTS: Rectal temperature was recorded each 30 minutes during surgery and at intensive care unit arrival. Patients in the study group had higher temperatures than the control group at all time points, and the difference reached statistical significance after 2 hours of surgery. Moreover, fewer patients in the study group suffered perioperative hypothermia (defined as rectal temperature <36 degrees C) than the control group (2/15 patients (13.3%) in the study group v 13/16 (81.3%) in the control group [p = 0.0006]). No difference in other outcomes was noted. None of the patients died in the hospital. There were no adverse events reported. CONCLUSIONS: The circulating-water garment, Allon ThermoWrapping Thermoregulation System, maintained normothermia during OPCAB surgery better than forced-air systems, especially after the first 2 hours of surgery, and it was not associated with surgical field disturbance.