Reducing diagnostic delay in hypophosphatasia: a case series of 14 patients presenting to general rheumatology.

OBJECTIVES: Hypophosphatasia (HPP) is a rare genetic metabolic bone disease that can cause chronic pain and fractures. Its hallmark is a persistently low serum ALP. HPP is now recognised by many osteoporosis specialists, but other specialists, such as rheumatologists and primary care physicians, may be less aware of this condition, causing diagnostic delay and possible harm to these patients. Our objective was to highlight features that can reduce this delay. METHODS: We retrospectively analysed 14 patients that presented with musculoskeletal pain to general rheumatology clinic at St. George's Hospital and were subsequently diagnosed with HPP. RESULTS: Median diagnostic delay was 13 years. All patients had an ALP below reference range for age and gender, with lowest mean ALP of 16 IU/L. All but one patient were women with median age of 51 years. Most common presentation was peripheral joint pain in 85.7% of patients. This was due to early-onset CPPD (calcium pyrophosphate deposition disease) in 71.4% of patients, osteoarthritis in 50%, or bursitis in 50%. Axial pain was reported in 64% of patients due to osteoarthritis or spinal stenosis. Fifty percent of patients had a history of long bone pain. Fifty percent had previous fracture(s). A total of 28.6% of patients had psoriatic arthritis, of which 1 patient had spondyloarthropathy, and 4 patients also had enthesitis. CONCLUSION: Patients with HPP can present to rheumatology with musculoskeletal pain, and if a persistently low ALP is confirmed, this may reduce the diagnostic delay of this rare disease. Similar to other rheumatologic patients, musculoskeletal pain in HPP was noted in peripheral joints and in the spine with almost a third of patients having psoriatic arthritis. Pain was also noted in the long bones, a feature consistent with metabolic bone disease. The diagnosis of HPP was also more likely in those patients with a personal or family history of dental disease or arthritis.

Impact of COVID-19 in hematopoietic stem cell transplant recipients: A systematic review and meta-analysis.

BACKGROUND: Hematopoietic stem cell transplant (HSCT) recipients are at increased risk of mortality and morbidity with coronavirus disease 2019 (COVID-19) due to severe immune dysfunction. METHODS: A literature search was performed on PubMed, Cochrane, and Clinical trials.gov from the date of inception to 12/08/2021. We identified 19 original studies reporting data on COVID-19 in HSCT recipients after screening 292 articles. Data were extracted following preferred reporting items for systematic reviews and meta-analysis guidelines. Quality evaluation was done using the National Institutes of Health (NIH) quality assessment tool. Inter-study variance was calculated using Der Simonian-Laird Estimator. Pooled analysis was conducted using MetaXL. A random-effects model was used to estimate the proportions with 95% confidence intervals (CI). RESULTS: Of 6711 patients in 19 studies, 2031 HSCT patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were analyzed. The median age of patients was 56.9 (range 1-81.6) years, and 63% patients were men according to 14 studies. The median time from transplant to SARS-CoV-2 infection for autologous (auto) and allogeneic (allo) HSCT patients was 23.2 (0.33-350.5) months and 16.4 (0.2-292.7) months, respectively. The median follow-up time after COVID-19 diagnosis was 28 (0-262) days. The COVID-19 mortality rate was 19% (95% CI 0.15-0.24, I2  = 76%, n = 373/2031). The pooled mortality rate was 17% (95% CI 0.12-0.24, I2  = 78%, n = 147/904) in auto-HSCT patients and 21% (95% CI 0.16-0.25, I2  = 60%, n = 231/1103) in allo-HSCT patients. CONCLUSIONS: HSCT recipients have a high risk of mortality and clinical complications due to COVID-19. There is a need for ongoing vigilance, masks, and social distancing, vaccination, and aggressive management of SARS-CoV-2 infection in HSCT recipients.

Pancreatic adenocarcinoma in liver transplant recipients: a case series.

BACKGROUND: Malignancy is one of the known leading causes of death among long-term liver transplantation (LT) survivors. Pancreatic cancer has an incidence of 7.6/100,000 in North America and constitutes a diagnostic challenge post-LT. METHODS: This is a single-center, retrospective review of the electronic health records (EHRs) of LT recipients with pancreatic adenocarcinoma (1990-2019). The prevalence of pancreatic adenocarcinoma in our institutional non-LT population was assessed using an institutional de-identified database (Synthetic Derivative). RESULTS: Six out of 2,232 (0.27%) LT recipients were diagnosed with pancreatic adenocarcinoma. Median age at diagnosis was 66.0 years (IQR, 57.8-71.8 years). Median time from LT to pancreatic adenocarcinoma diagnosis was 8.9 years (IQR, 4.7-16.2 years), the median size on imaging was 3.2 cm (IQR, 3.1-4.7 cm), and all tumors were located on the head of the pancreas. Three patients underwent surgical resection (one with adjuvant chemotherapy), two underwent palliative care, and one palliative chemotherapy with gemcitabine and abraxane. Over a median follow-up of 220.5 days (IQR, 144.8-399.5 days), all six patients died due to disease progression (100%). Pancreatic adenocarcinoma was diagnosed in 5,033 out of 2,484,772 (0.20%) individuals in the Synthetic Derivative. CONCLUSIONS: Our findings identified an increased incidence of pancreatic adenocarcinoma following LT compared to the general population.

Liver Transplantation for Cholangiocarcinoma: Charting a Path With Lessons Learned From Center Experience.

BACKGROUND: While liver transplantation (LT) with neoadjuvant chemoradiation is increasingly utilized for the management of unresectable cholangiocarcinoma (CCA), data on post-LT survival are limited. METHODS: We identified 844 patients who underwent LT (2002-2019) for nonincidental (CCA listing) or incidental (CCA on explant, not at listing) CCA in the Scientific Registry of Transplant Recipients. Kaplan-Meier and multivariable proportional hazards regression methods evaluated the effects of patient characteristics, donor type, transplant era (before/after 2010), and center volume (center-level CCALTs/active year) on the risk of graft failure and patient mortality. RESULTS: One center performed >12 CCALTs/y, and the rest performed ≤4. Five-year graft survival was 50.6%. Multivariable models demonstrated laboratory model of end-stage liver disease ≥40 versus <15 and center volumes of 1, >1 to ≤2, and >2 to ≤4 CCALTs/y compared to >12 were associated with increased risk of graft failure and mortality (all P ≤ 0.002). Extra vessel use was associated with center volume. Among all recipients, extra vessel use occurred in 55.4% of CCALTs performed at the highest volume center and in 14.0% of cases at centers having ≤4 CCAs/y (P < 0.05). CONCLUSIONS: Center volume-related differences in outcomes and extra vessel use highlight the importance of establishing a unified, effective treatment protocol and the potential utility of regionalization of LT for CCA.

Management of hepatoblastoma in the United States: Can we do better?

BACKGROUND: Hepatoblastoma is the most common type of liver cancer in children. Refined therapeutic approaches combining risk-adapted chemotherapy along with complete tumor resection has led to improved survival. We aimed to evaluate the current state of management and outcomes for hepatoblastoma in the United States. METHODS: We retrospectively reviewed 794 children (<18 years) with hepatoblastoma from the National Cancer Database (2004-2015). We assessed overall survival by means of Kaplan-Meier method, log-rank tests, and multivariable Cox regression. RESULTS: Median age was 1 year (interquartile range: 0-2) and 170 (21.4%) presented with metastatic disease. Surgical resection was included in the treatment of 614 (77.3%) children (resection in 66.8% and liver transplantation in 10.6%). In the entire cohort, 95.1% of children received chemotherapy. In the surgical cohort, 575 (93.6%) received chemotherapy (34.5% neoadjuvant, 28.7% adjuvant, 30.5% both neoadjuvant and adjuvant). The 5-year overall survival was 76.6% for the entire cohort (no-surgery group: 55.3% vs surgery group: 82.8%). In multivariable analysis for all children, age ≥8 years (P = .009), metastasis (P < .001), surgery only (P = .009), and chemotherapy only (P < .001) were risk factors for mortality. In multivariable analysis for the surgical cohort, metastasis (P = .001), multifocality (P = .02), no chemotherapy (P = .03), and margin-positive resection (P = .02) were risk factors for mortality. CONCLUSION: Excellent long-term overall survival is achievable with a combination of chemotherapy and surgical resection when a negative resection margin is achieved. However, nearly a quarter of children never received surgical treatment, representing a potential opportunity for improvement in care.

Effect of Donor Transaminase Levels on Graft Survival Following Liver Transplant: An Analysis of the Organ Procurement and Transplantation Network Database.

OBJECTIVES: Despite data showing equivalent outcomes between grafts from marginal versus standard criteria deceased liver donors, elevated donor transaminases constitute a frequent reason to decline potential livers. We assessed the effect of donor transaminase levels and other characteristics on graft survival. MATERIALS AND METHODS: We performed a retrospective cohort analysis of adult first deceased donor liver transplant recipients with available transaminase levels registered in the Organ Procurement and Transplantation Network database (2008-2018). We used Cox proportional hazards regression to determine the effects of donor characteristics on graft survival. RESULTS: Of 53 913 liver transplants, 52 158 were allografts from donors with low transaminases (≤ 500 U/L; group A) and 1755 were from donors with elevated transaminases (> 500 U/L; group B). Group A recipients were more likely to be hospitalized (P = .01) or in intensive care (P < .001) or to have mechanical assistance (P < .001), portal vein thrombosis (P = .01), diabetes mellitus (P = .003), or dialysis the week before liver transplant (P = .004). Multivariable analysis (controlling for recipient characteristics) showed donor risk factors of graft failure included diabetes mellitus (P < .001), donation after cardiac death (P < .001), total bilirubin > 3.5 mg/dL (P < .001), serum creatinine > 1.5 mg/dL (P = .01), and cold ischemia time > 6 hours (P < .001). Regional organ sharing showed lower risk of graft failure (P = .02). Donor transaminases > 500 U/L were not associated with graft failure (relative risk, 1.02; 95% CI, 0.91-1.14; P = .74). CONCLUSIONS: Donor transaminases > 500 U/L should not preclude the use of liver grafts. Instead, donor total bilirubin > 3.5 mg/dL and serum creatinine > 1.5 mg/dL appear to be associated with higher likelihood of graft failure after liver transplant.

Adult Combined Heart-Liver Transplantation: The United States Experience.

Background: We aimed to review the indications and outcomes of adults undergoing combined heart-liver transplantation (CHLT) in the US using national registry data. Methods: Adult (≥18 years) CHLT recipients in the United Network for Organ Sharing database were included (09/1987-09/2020; era 1 = 1989-2000, era 2 = 2001-2010, era 3 = 2011-2020). Survival analysis was conducted by means of Kaplan-Meier method, log-rank test, and Cox regression. Results: We identified 369 adults receiving CHLT between 12/1989-08/2020. The number of adult CHLT recipients (R2 = 0.75, p < 0.001) and centers performing CHLT (R2 = 0.80, p < 0.001) have increased over the study period. The most common cardiac diagnosis in the first two eras was restrictive/infiltrative cardiomyopathy, while the most common in era 3 was congenital heart disease (p = 0.03). The 1-, 3-, and 5-years patient survival was 86.8, 80.1, and 77.9%, respectively. In multivariable analysis, recipient diabetes [adjusted hazard ratio (aHR) = 2.35, 95% CI: 1.23-4.48], CHLT between 1989-2000 compared with 2011-2020 (aHR = 5.00, 95% CI: 1.13-22.26), and sequential-liver first CHLT compared with sequential-heart first CHLT (aHR = 2.44, 95% CI: 1.15-5.18) were associated with increased risk of mortality. Higher left ventricular ejection fraction was associated with decreased risk of mortality (aHR = 0.96, 95% CI: 0.92-0.99). Conclusion: CHLT is being increasingly performed with evolving indications. Excellent outcomes can be achieved with multidisciplinary patient and donor selection and surgical planning.

Mortality Determinants in Children with Biliary Atresia Awaiting Liver Transplantation.

OBJECTIVE: To determine risk factors for waitlist mortality in children with biliary atresia listed for liver transplantation. STUDY DESIGN: There were 2704 children with biliary atresia (<12 years of age) listed for a first liver transplant (2002-2018) in the United Network for Organ Sharing database. Fine-Gray regression models for competing risks analysis (main risk = waitlist mortality/delisting owing to too sick; competing risk = liver transplantation) were implemented to identify risk factors for waitlist mortality. RESULTS: The median waitlist time was 83 days (IQR, 34-191). The cumulative incidence of waitlist mortality was 5.2%. In multivariable analysis (n = 2253), increasing bilirubin level (P < .001), portal vein thrombosis (P = .03), and ventilator dependence (P < .001) at listing were associated with a higher risk, whereas weight ≥10 kg at listing (P = .009) was associated with a lower risk of waitlist mortality. When ascites at listing was included in multivariable analysis (n = 1376), it was associated with a higher risk for the composite outcome (P = .03). Encephalopathy at listing was not associated with waitlist mortality (n = 1376; P = .15). CONCLUSIONS: These parameters can be used to more objectively prioritize children with biliary atresia awaiting liver transplantation and identify children with biliary atresia-related end-stage liver disease at high-risk of mortality.

Surgical management of pediatric hepatocellular carcinoma: An analysis of the National Cancer Database.

PURPOSE: This study evaluates overall survival (OS) between liver transplantation (LT) and liver resection (LR), while assessing the effect of margin status, in children with hepatocellular carcinoma (HCC). METHODS: The National Cancer Database was queried (2004-2015) for children (<18 years) with non-metastatic HCC undergoing surgery. RESULTS: One hundred six children with HCC treated surgically (LT 34, LR 72) were identified. For T1 stage, no difference in OS was observed for LT vs. margin-negative liver resection [LR(-)] (log-rank, p = 0.47). For T2/T3/T4 stage, no difference in OS was observed for LT vs. LR(-) (log-rank, p = 0.08); both subgroups exhibited superior OS vs. margin-positive liver resection [LR(+)] (log-rank, LT vs. LR(+): p = 0.001 and LR(-) vs. LR(+): p = 0.04). On multivariable Cox regression: (i) histology (fibrolamellar vs. not) and T stage (T1 vs. T2/T3/T4) were not associated with OS (both p = 0.06), (ii) chemotherapy and size >5 cm were not associated with OS (both p ≥ 0.42), (iii) when compared to LT, both LR(-) (p = 0.03) and LR(+) (p = 0.001) were associated with increased likelihood of mortality. CONCLUSION: Although margin-negative resection may be obtained with LT or LR, early LT consultation is warranted for children at high risk of LR(+) regardless of Milan criteria due to the negative impact of LR(+) on OS. TYPE OF STUDY: Retrospective cohort study. LEVEL OF EVIDENCE: III.

Extracorporeal Membrane Oxygenation in Pediatric Liver Transplantation: A Multicenter Linked Database Analysis and Systematic Review of the Literature.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) can be used to maintain oxygen delivery and provide hemodynamic support in case of circulatory and respiratory failure. Although the role of ECMO has emerged in the setting of adult liver transplantation (LT), data in children are limited. We aimed to describe the characteristics and outcomes of children receiving ECMO support at the time of or following LT. METHODS: All pediatric LT recipients (≤20 y) requiring ECMO support peri-/post-LT were identified from a linked Pediatric Health Information System/Scientific Registry of Transplant Recipients dataset (2002-2018). The Kaplan-Meier method and Cox regression analysis were used to assess post-ECMO survival. A systematic literature review was conducted in accordance with the PRISMA statement. RESULTS: Thirty-four children required ECMO peri-/post-LT. The median time from LT to ECMO was 5 d (interquartile range, 0.0-12.3), and the median ECMO duration was 1 d (interquartile range, 1.0-6.3). Children started on ECMO within 1 d of LT exhibited superior survival compared with those started on ECMO later (P = 0.03). When adjusting for recipient weight, increasing time from LT to ECMO initiation was associated with increased risk of mortality (hazard ratio, 1.03; 95% confidence interval, 1.00-1.06; P = 0.049). Overall, 55.9% (n = 19 of 34) of the patients survived. Twenty-two children receiving ECMO in the peri-/post-LT period were systematically reviewed, and 15 of them survived (68.2%). CONCLUSIONS: With an encouraging >55% patient survival at 6 mo, ECMO should be considered as a viable option in pediatric LT recipients with potentially reversible severe respiratory or cardiovascular failure refractory to conventional treatment.

Feasibility of Serial Ultrasound Measurements of the Rectus Femoris Muscle Area to Assess Muscle Loss in Patients Awaiting Liver Transplantation in the Intensive Care Unit.

End-stage liver disease (ESLD) patients requiring intensive care unit (ICU) care before liver transplantation (LT) often experience significant muscle mass loss, which has been associated with mortality. In this exploratory study, we primarily aimed to assess the feasibility of serial ultrasound (US) rectus femoris muscle area (RFMA) measurements for the evaluation of progressive muscle loss in ICU-bound potential LT candidates and describe the rate of muscle loss as assessed by sequential US RFMA measurements. Secondarily, we sought to identify patient characteristics associated with muscle loss and determine how muscle loss is associated with survival. METHODS: We prospectively enrolled 50 ESLD adults (≥18 y old) undergoing evaluation for LT candidacy in the ICU. A baseline computed tomography measurement of psoas muscle area (PMA) and serial bedside US measurements of RFMA were obtained. The associations between patient characteristics, PMA, RFMA, ICU stay, and survival were analyzed. RESULTS: Rapid decline in muscle mass by RFMA measurements was ubiquitously present and correlated to baseline PMA and length of ICU stay. RFMA normalized by body surface area decreased by 0.013 cm2/m2 (95% confidence interval, 0.010-0.016; P < 0.001) for each day in the ICU. Decreased RFMA normalized by body surface area was associated with poor overall survival (adjusted hazard ratio, 0.42; 95% confidence interval, 0.18-0.99; P = 0.047). CONCLUSIONS: In this exploratory, prospective study, serial US RFMA measurements in ESLD patients in the ICU are feasible, demonstrate progressive time-dependent muscle loss, and are associated with mortality. Further large-scale assessment of this modality compared with static PMA or performance-based dynamic assessments should be performed.

Applicants' Interview Experience of Family Medicine Residency Match: Reflections from a Quality Improvement Initiative at a Community Hospital.

Background and objective Both family medicine applicants and programs dedicate significant resources to the interview process, a time for both parties to make an impression on the other in an attempt to find their best match. Despite the importance of this process, little research has been completed to ensure the process efficiently addresses applicant preferences on interview day and the surrounding process. This study aimed to determine the factors influencing the family medicine applicant preferences regarding the pre-interview, interview, and post-interview ranking process.  Methods The study method was a cross-sectional electronic survey utilizing anonymous questionnaires that assessed demographics, pre-interview, interview, post-interview ranking preference, and applicants' experiences applying to a community-based family medicine residency program after their interview for the 2020 application cycle. Results Out of the 106 family medicine applicants, 48 responded; 52.08% were males, 52.5% were married, 58.33% applicants were from the osteopathic medical school, 33.33% were from the allopathic Liaison Committee on Medical Education (LCME) non accredited medical school/international medical graduates (IMG's), and 8.33% were from the allopathic LCME accredited medical schools. Free hotel accommodation was not offered from half of the programs to 27.8% of the applicants in the 2020 match cycle (pre-pandemic). Respondents favored electronic means of scheduling interviews with a positive experience with the online self-scheduling Electronic Residency Application Service (ERAS) calendar. A significantly higher proportion of IMGs applied to a higher number of family medicine programs followed by the osteopathic applicants. There was no statistical difference found between osteopathic and allopathic applicants for the number of programs they got invited to; however, the difference was significant for osteopathic and allopathic LCME accredited applicants who interviewed and ranked programs in the range of 11-20 (62.96%, p=0.0013 and 66.67%, p=0.0018, respectively). The respondents' most important experiences were interviewing the program director, faculty members, and tour the hospital facility. When ranking programs, these family medicine applicants considered the strength of program training, the quality of current residents, and the program's geographic location as the top three most significant factors, with mean importance ratings of 5.08, 5.02, and 4.35, respectively. Applicants also considered how the current residents perceive the program director, prior teaching experience, and program diversity with mean importance ratings of 3.42, 2.89, and 2.09, respectively. Conclusion Although applicants' preferences for family medicine residency programs are similar to generally reported by The National Resident Matching Program (NRMP) surveys, some key differences do exist. The program leadership should consider these preferences from the candidates' perspective for a successful match in family medicine residency on both sides.

Oxidoreductases for the remediation of organic pollutants in water - a critical review.

Water contamination by various recalcitrant organic aromatic compounds is an emerging environmental issue that is increasingly attracting the attention of environmental scientists. A great majority of these recalcitrant pollutants are industrial wastes, textile dyes, pharmaceuticals, hormones, and personal care products that are discharged into wastewater. Not surprisingly, various chemical, physical, and biological strategies have been proposed and developed to remove and/or degrade these pollutants from contaminated water bodies. Biological approaches, specifically using oxidoreductase enzymes (such as peroxidases and laccases) for pollutant degradation are a relatively new and a promising research area that has potential advantages over other methods due to their higher efficiency and the ease of handling. This review focuses on the application of different classes of oxidoreductase enzymes to degrade various classes of organic pollutants. In addition to classifying these enzymes based on structural differences, the major factors that can affect their remediation ability, such as the class of peroxidases employed, pH, molecular structure of the pollutant, temperature, and the presence of redox mediators are also examined and discussed. Interestingly, a literature survey combined with our unpublished data suggests that "peroxidases" are a very heterogeneous and diverse family of enzymes and have different pH profiles, temperature optima, thermal stabilities, requirements for redox mediators, and substrate specificities as well as varying detoxification abilities. Additionally, remediation of real-life polluted samples by oxidoreductases is also highlighted as well as a critical look at current challenges and future perspectives.

Clinical diagnostic tools for vitamin D assessment.

Vitamin D deficiency has been implicated in a plethora of diseases including rheumatoid arthritis, Parkinson's disease, Alzheimer's disease, and osteoporosis. Deficiency of this vitamin is a global epidemic affecting both developing and developed nations. Within a clinical context, the qualitative and quantitative analysis of vitamin D is therefore vital. The main metabolic markers for assessing vitamin D status in humans are the hydroxylated forms of vitamin D, 25OHD3 and 25OHD2 on account of their long half-lives within the body and excellent stability. An adequate level for healthy individuals of these hydroxylated forms is estimated to be around 20-40ng/ml of blood. There are three main analytical techniques for determining the levels of 25OHD3 and 25OHD2. The first technique is immunoassay-based and can be performed in a rapid, high throughput, automated manner, allowing as many as 240 tests per hour with the duration of each assay as little as 18min. Furthermore, it offers excellent sensitivity with a detection range of 3.4-156ng/ml. A major downside of immunoassays is that they are unable to distinguish between the various forms of vitamin D. While HPLC is a highthroughput low cost instrument it is not a very sensitive technique and cannot quantify the down stream metabolites of vitamin D. The third technique, namely liquid chromatography-mass spectrometry (LC-MS/), provides excellent sensitivity with a wide dynamic range from 0.068pg/ml to 100ng/ml. Additionally, it offers a high level of separation and permits identification of vitamin D-related metabolites. However, a huge limitation with LC/MS/MS is their poor throughput for sample analyses. As yet, there is no analytical technique which combines the fine detection capabilities of LC/MS/MS and the rapid, automated format of immunoassay, for vitamin D analyses. Future attention therefore needs to be given to this area if the current clinical diagnostic tools for vitamin D analysis are to be further improved.

Comparative Degradation of a Thiazole Pollutant by an Advanced Oxidation Process and an Enzymatic Approach.

Organic pollutants, especially those found in water bodies, pose a direct threat to various aquatic organisms as well as humans. A variety of different remediation approaches, including chemical and biological methods, have been developed for the degradation of various organic pollutants. However, comparative mechanistic studies of pollutant degradation by these different systems are almost non-existent. In this study, the degradation of a model thiazole pollutant, thioflavin T (ThT), was carried out in the presence of either an advanced oxidation process (ultraviolet (UV) + H2O2) or a chloroperoxidase enzyme system (CPO + H2O2). The degradation was followed both spectrophotometrically and using liquid chromatography-mass spectroscopy (LC-MS), and the products formed were identified using tandem liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS). The results show that the two remediation approaches produced different sets of intermediates, with only one common species (a demethylated form of ThT). This suggests that different degradation schemes were operating in the two systems. Interestingly, one of the major intermediates produced by the CPO + H2O2 system was a chlorinated form of thioflavin. Phytotoxicity studies showed that the CPO + H2O2-treated ThT solution was significantly (p <0.05) less toxic than the UV + H2O2-treated ThT solution. This is the first time that a comparative mechanistic study showing in detail the intermediates generated in chemical and biological remediation methods has been presented. Furthermore, the results show that different remediation systems have very different degradation schemes and result in products having different toxicities.

Soybean peroxidase-mediated degradation of an azo dye- a detailed mechanistic study.

BACKGROUND: Peroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published. RESULTS: In the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process. CONCLUSIONS: Detailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids.

Mechanistic study of a diazo dye degradation by Soybean Peroxidase.

BACKGROUND: Enzyme based remediation of wastewater is emerging as a novel, efficient and environmentally-friendlier approach. However, studies showing detailed mechanisms of enzyme mediated degradation of organic pollutants are not widely published. RESULTS: The present report describes a detailed study on the use of Soybean Peroxidase to efficiently degrade Trypan Blue, a diazo dye. In addition to examining various parameters that can affect the dye degradation ability of the enzyme, such as enzyme and H2O2 concentration, reaction pH and temperature, we carried out a detailed mechanistic study of Trypan Blue degradation. HPLC-DAD and LC-MS/MS studies were carried out to confirm dye degradation and analyze the intermediate metabolites and develop a detailed mechanistic dye degradation pathway. CONCLUSION: We report that Soybean peroxidase causes Trypan Blue degradation via symmetrical azo bond cleavage and subsequent radical-initiated ring opening of the metabolites. Interestingly, our results also show that no high molecular weight polymers were produced during the peroxidase-H2O2 mediated degradation of the phenolic Trypan Blue.

Determination of optimum operating conditions of carmine decoloration by UV/H2O2 using response surface methodology.

In this study, the photolytic decoloration of carmine (C.I. Natural Red 4) via UV radiation in the presence of H2O2 was optimized using response surface methodology (RSM). According to analysis of variance (ANOVA) results, the proposed model can be used to navigate the design space. It was found that the response of carmine degradation is very sensitive to the independent factors of carmine concentration, H2O2 concentration, pH and reaction time. The proposed model for D-optimal design fitted very well with the experimental data with R2 and R(adj)2 correlation coefficients of 0.998 and 0.997, respectively.

Solvent effect on the spectral properties of Neutral Red.

BACKGROUND: The study was aimed at investigating the effect of various solvents on the absorption spectra of Neutral Red, a dye belonging to the quinone-imine class of dyes. The solvents chosen for the study were water, ethanol, acetonitrile, acetone, propan-1-ol, chloroform, nitrobenzene, ethyleneglycol, acetic acid, DMSO and DMF. RESULTS: The results have shown that the absorption maxima of dyes are dependent on solvent polarity. In non-hydrogen-bond donating solvents, solvation of dye molecules probably occurs via dipole-dipole interactions, whereas in hydrogen-bond donating solvents the phenomenon is more hydrogen bonding in nature. To estimate the contribution of the different variables on the wave number of the Neutral Red dye, regression analyses using the ECW model were compared with the pi* scale model. This showed that the unified scale for estimating the solvent effect on the absorption of the Neutral Red dye is more adopted and more applicable than the pi* scale model. CONCLUSION: Absorption maxima of dyes are dependent on solvent polarity. Solvation of dye molecules probably occurs via dipole-dipole interactions in non-hydrogen-bond donating solvents, whereas in hydrogen-bond donating solvents the phenomenon is more hydrogen bonding in nature. The unified scale for estimating the solvent effect on the absorption of Neutral Red dye is more adopted and more applicable than the pi* scale model. This may be due to complications from both pi-pi* charge transfer interactions and incomplete complexation of the solute; these effects are averaged out in the derived beta and pi parameters and thus limit their applicability.