The Science of the Modern Kitchen.

The kitchen offers chemists an opportunity to cook up chemistry using everyday ingredients. This is the inspiration behind 'The Science of the Modern Kitchen', a chemistry course offered to non-science undergraduates.

Using a high-throughput, whole-cell hydrogenase assay to identify potential small molecule inhibitors of [NiFe]-hydrogenase.

[NiFe]-hydrogenases are used by several human pathogens to catalyze the reversible conversion between molecular hydrogen and protons and electrons. Hydrogenases provide an increased metabolic flexibility for pathogens, such as Escherichia coli and Helicobacter pylori, by allowing the use of molecular hydrogen as an energy source to promote survival in anaerobic environments. With the rise of antimicrobial resistance and the desire for novel therapeutics, the [NiFe]-hydrogenases are alluring targets. Inhibiting the nickel insertion pathway of [NiFe]-hydrogenases is attractive as this pathway is required for the generation of functional enzymes and is orthogonal to human biochemistry. In this work, nickel availability for the production and function of E. coli [NiFe]-hydrogenase was explored through immunoblot and activity assays. Whole-cell hydrogenase activities were assayed in high throughput against a small molecule library of known bioactives. Iodoquinol was identified as a potential inhibitor of the nickel biosynthetic pathway of [NiFe]-hydrogenase through a two-step screening process, but further studies with immunoblot assays showed confounding effects dependent on the cell growth phase. This study highlights the significance of considering the growth phenotype for whole-cell based assays overall and its effects on various cellular processes influenced by metal trafficking and homeostasis.

Contralateral prophylactic mastectomy at the time of delayed microvascular breast reconstruction adversely affects patient-reported outcomes: A retrospective cohort study.

PURPOSE: An increasing number of women with unilateral breast cancer are seeking bilateral mastectomies and reconstruction. At our centre, many women who have undergone previous unilateral therapeutic mastectomy request contralateral prophylactic mastectomy (CPM) at the time of delayed reconstruction. These mixed timing reconstructions are particularly challenging as patients have an immediate reconstruction on one side and delayed reconstruction on the other, which may result in asymmetry. This retrospective cohort study evaluates patient-reported satisfaction following mixed timing breast reconstruction and compares them to unilateral delayed reconstruction. METHODS: One hundred and forty-one patients who underwent successful deep inferior epigastric artery perforator (DIEP) flap breast reconstruction and completed baseline and 12-month BREAST-Qs were included in the study. Patient-reported outcomes following bilateral mixed timing reconstruction (n = 56) were compared to those of unilateral delayed reconstruction (UDR) without CPM (n = 85). RESULTS: Women who sought CPM were significantly younger and had lower annual incomes when compared with those who underwent unilateral reconstruction. Mixed timing reconstruction was associated with significantly lower levels of breast satisfaction and psychosocial function as compared to UDR at 12 months post-operatively. BREAST-Q scores (18 months) were available for 75 patients in the cohort and indicated that this decreased breast satisfaction and psychosocial impairment was sustained in the longer-term. CONCLUSIONS: Patients who seek CPM at the time of delayed reconstruction should be advised that this is associated with lower levels of breast satisfaction and psychosocial well-being as compared to unilateral delayed breast reconstruction.

Development and Evaluation of a Machine Learning Prediction Model for Flap Failure in Microvascular Breast Reconstruction.

BACKGROUND: Despite high success rates, flap failure remains an inherent risk in microvascular breast reconstruction. Identifying patients who are at high risk for flap failure would enable us to recommend alternative reconstructive techniques. However, as flap failure is a rare event, identification of risk factors is statistically challenging. Machine learning is a form of artificial intelligence that automates analytical model building. It has been proposed that machine learning can build superior prediction models when the outcome of interest is rare. METHODS: In this study we evaluate machine learning resampling and decision-tree classification models for the prediction of flap failure in a large retrospective cohort of microvascular breast reconstructions. RESULTS: A total of 1012 patients were included in the study. Twelve patients (1.1%) experienced flap failure. The ROSE informed oversampling technique and decision-tree classification resulted in a strong prediction model (AUC 0.95) with high sensitivity and specificity. In the testing cohort, the model maintained acceptable specificity and predictive power (AUC 0.67), but sensitivity was reduced. The model identified four high-risk patient groups. Obesity, comorbidities and smoking were found to contribute to flap loss. The flap failure rate in high-risk patients was 7.8% compared with 0.44% in the low-risk cohort (p = 0.001). CONCLUSIONS: This machine-learning risk prediction model suggests that flap failure may not be a random event. The algorithm indicates that flap failure is multifactorial and identifies a number of potential contributing factors that warrant further investigation.

Development and validation of a risk stratification model for immediate microvascular breast reconstruction.

BACKGROUND: Immediate breast reconstruction has many advantages but is associated with higher complication rates than delayed reconstruction. Complications can delay the delivery of adjuvant cancer treatments. This study aimed to develop and validate a risk stratification model for the prediction of perioperative complications in immediate microvascular breast reconstruction. METHODS: The association between patient and treatment variables and perioperative complications was evaluated in a retrospective cohort of 351 women undergoing immediate breast reconstruction using free deep inferior epigastric artery perforator flaps. Multivariable logistic regression was used to determine the strength of association and weighted scores were assigned. Using cumulative risk scores, patients were stratified into low, intermediate, and high-risk groups. The model was then validated in a prospective cohort of 100 consecutive patients. RESULTS: Obesity, smoking, prior radiation, and comorbidities were important predictors and incorporated into the risk model. Complications occurred in 23.5% of low-risk (95% confidence interval [CI] = 17.7-29.2), 38.4% of intermediate-risk (95% CI = 29.2-47.5) and 53.9% of high-risk (95% CI = 33.3-74.4) patients. Validation confirmed a linear relationship between the risk stratification categories and complications in a model with good predictive power (c-statistic = 0.7, 95% CI = 0.6-0.8). CONCLUSION: A simple risk score, based on known preoperative variables, provides accurate risk stratification for patients considering immediate microvascular breast reconstruction.

A whole-cell, high-throughput hydrogenase assay to identify factors that modulate [NiFe]-hydrogenase activity.

[NiFe]-hydrogenases have attracted attention as potential therapeutic targets or components of a hydrogen-based economy. [NiFe]-hydrogenase production is a complicated process that requires many associated accessory proteins that supply the requisite cofactors and substrates. Current methods for measuring hydrogenase activity have low throughput and often require specialized conditions and reagents. In this work, we developed a whole-cell high-throughput hydrogenase assay based on the colorimetric reduction of benzyl viologen to explore the biological networks of these enzymes in Escherichia coli We utilized this assay to screen the Keio collection, a set of nonlethal single-gene knockouts in E. coli BW25113. The results of this screen highlighted the assay's specificity and revealed known components of the intricate network of systems that underwrite [NiFe]-hydrogenase activity, including nickel homeostasis and formate dehydrogenase activities as well as molybdopterin and selenocysteine biosynthetic pathways. The screen also helped identify several new genetic components that modulate hydrogenase activity. We examined one E. coli strain with undetectable hydrogenase activity in more detail (ΔeutK), finding that nickel delivery to the enzyme active site was completely abrogated, and tracked this effect to an ancillary and unannotated lack of the fumarate and nitrate reduction (FNR) anaerobic regulatory protein. Collectively, these results demonstrate that the whole-cell assay developed here can be used to uncover new information about bacterial [NiFe]-hydrogenase production and to probe the cellular components of microbial nickel homeostasis.

Synergistic Interaction Increases Complication Rates following Microvascular Breast Reconstruction.

BACKGROUND: Microvascular breast reconstruction is a complex procedure that can be associated with high complication rates. Although a number of individual predictors of perioperative complications have been identified, few studies have explored interaction between risk factors. Understanding the synergistic effects of multiple risk factors is central to accurate and personalized preoperative risk prediction. METHODS: The authors conducted a retrospective cohort study of patients who underwent microvascular breast reconstruction at their institution between 2009 and 2017. All intraoperative and postoperative complications were recorded. A multivariable logistic regression exploratory model identified independent predictors of complications. Interactions between individual variables were then assessed using the relative excess risk index (RERI) and the synergy index (SI). RESULTS: Nine hundred twelve patients were included in the study and 26.1 percent experienced at least one perioperative complication. Obesity (OR, 1.54; p = 0.009), immediate reconstruction (OR, 1.49; p = 0.028), and comorbidities (OR, 1.43; p = 0.033) were identified as independent predictors of complications. Obesity and comorbidities had significant synergistic interactions with immediate reconstruction (RERI, 0.86; SI, 2.35; p = 0.0002; and RERI, 0.54; SI, 1.78; p = 0.001), bilateral reconstruction (RERI, 0.12; SI, 1.15; p = 0.002; and RERI, 0.59; SI, 3.16; p = 0.005), and previous radiotherapy (RERI, 0.62; SI, 4.43; p = 0.01; and RERI, 0.11; SI, 1.23; p = 0.040). Patients undergoing immediate breast reconstruction who were both obese and smokers had a 12-fold increase in complication rates (OR, 12.68; 95 percent CI, 1.36 to 118.46; p = 0.026) with a very strong synergistic interaction between variables (RERI, 10.55; SI, 10.33). CONCLUSION: Patient- and treatment-related variables interact in a synergistic manner to increase the risk of complications following microvascular breast reconstruction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Increasing body mass index increases complications but not failure rates in microvascular breast reconstruction: A retrospective cohort study.

BACKGROUND: Obesity is often considered a relative contra-indication for microvascular autologous breast reconstruction. We hypothesize that although obesity is associated with increased post-operative complications, abdominally based microvascular post mastectomy breast reconstruction can still be achieved with high rates of success. This study analyses the relationship between increasing body mass index (BMI) and post-operative complications at a high volume specialist centre, with a particular focus on serious complications. METHODS AND RESULTS: Nine hundred and sixty patients undergoing 1460 microvascular breast reconstructions were included in the study. Obese patients (BMI ≥ 30 kg/m2) accounted for 37.7% of the cohort and were more likely to have co-morbidities, a history of smoking and bilateral reconstruction. Post-operative surgical complications occurred in 156 patients (16.3%) and medical complications occurred in 10 patients (1.0%). There was no significant difference between the flap failure rates in patients with normal BMI < 25 kg/m2 (1.2% of patients, 0.9% of flaps) and obese patients (1.9% of patients, 1.2% of flaps, p = 0.07). Obesity was an independent predictor of overall complications (OR 1.7, CI 0.81-2.74, p = 0.001) but not medical complications or flap failure (OR 1.3, CI 0.43-5.8, p = 0.161 and OR 1.2, CI 0.66-6.1, p = 0.091). There was a linear relationship between increasing BMI and overall complication rates, but serious complications remained uncommon even in morbidly obese patients. CONCLUSION: This large single-centre study demonstrates that although obesity increases the risk of overall complications, microvascular breast reconstruction can be safely and successfully achieved in the vast majority of patients. Obese patients should be carefully counselled pre-operatively, but increased BMI should not be considered a contra-indication for microvascular breast reconstruction.

Predicting complications in immediate microvascular breast reconstruction: Validity of the breast reconstruction assessment (BRA) surgical risk calculator.

BACKGROUND: The Breast Reconstruction Assessment (BRA)-score is a disease-specific risk calculator that estimates the likelihood of postoperative complications in an individual patient. The tool has not been previously externally validated in microvascular breast reconstruction. The purpose of this study was to evaluate the efficacy of the calculator in patients who underwent microvascular reconstruction at a single specialist institution. METHODS: Data from 415 patients who had immediate microvascular breast reconstruction were entered into the calculator. The predicted and observed rates of surgical complications, medical complications, reoperation, and total or partial flap failure were compared. The accuracy of the calculator was assessed using statistical measures of calibration and discrimination. RESULTS: The calculator accurately predicted the proportion of patients who would experience surgical complications and reoperations but overestimated the rates of medical complications and flap failures. The C-statistics were low for all four prediction models (0.49-0.59), suggesting weak discriminatory power, and the Brier scores were relatively high (0.09-0.44), indicating poor correlation between predicted and actual probability of complications. CONCLUSION: These results suggest that the BRA score cannot accurately identify patients at risk for complications following immediate microvascular breast reconstruction at our institution.