Right mini-parasternotomy may be a good minimally invasive alternative to full sternotomy for cardiac valve operations-a propensity-adjusted analysis

AIM

Limited realworld data existed for miniparasternotomy approach with good sample size in Asian cohorts and most previous studies were eclipsed by case heterogeneity. The goal of this study was to compare safety and quality outcomes of cardiac noncoronary valve operations by miniparasternotomy and full sternotomy approaches on riskadjusted basis.

METHODS

From our hospital database, we retrieved the cases of non-coronary valve operations from 1 January 2005 to 31 December 2012, including re-do, emergent, and combined procedures. Estimated EuroScore-II and propensity score for choosing mini-parasternotomy were adjusted for in the regression models on hospital mortality, complications (pneumonia, stroke, sepsis, etc.), and quality parameters (length of stay, ICU time, ventilator time, etc.). Non-complicated cases, defined as survival to discharge, ventilator use not over one week, and intensive care unit stay not over two weeks, were used for quality parameters.

RESULTS

There were 283 miniparasternotomy and 177 full sternotomy cases. EuroScore-II differed significantly (medians 2.1 vs. 4.7, p<0.001). Propensity scores for choosing miniparasternotomy were higher with lower EuroScore-II (OR=0.91 per 1%, p<0.001), aortic regurgitation (OR=2.3, p=0.005), and aortic non-mitral valve disease (OR=3.9, p<0.001). Adjusted for propensity score and EuroScore-II, mini-parasternotomy group had less pneumonia (OR=0.32, p=0.043), less sepsis (OR=0.31, p=0.045), and shorter non-complicated length of stay (coefficient=7.2 (day), p<0.001) than full sternotomy group, whereas Kaplan-Meier survival, non-complicated ICU time, non-complicated ventilator time, and 30-day mortality did not differ significantly.

CONCLUSION

The propensity-adjusted analysis demonstrated encouraging safety and quality outcomes for mini-parasternotomy valve operation in carefully selected patients.

Concern and risk perception of osteoporosis and fracture among post-menopausal Australian women: results from the Global Longitudinal Study of Osteoporosis in Women (GLOW) cohort

PURPOSE

The purpose of this study is to identify factors associated with concern and perception of risks of osteoporosis and osteoporotic fractures and determine whether bone mineral density (BMD) testing influenced concern and risk perception.

METHODS

Study subjects (n = 1,082, age 55-94 years) were female Australian participants of the Global Longitudinal Study of Osteoporosis in Women (GLOW). Self-administered questionnaires were sent annually from 2007 to 2010. Study outcomes included 'concern about osteoporosis', 'perception of getting osteoporosis' and 'perception of fracture risk' compared to similar aged women. The closest post-BMD testing or baseline questionnaires were used for women with and without BMD testing, respectively. Multinomial logistic regression was used for the analysis.

RESULTS

BMD testing, prior fracture after age 45, younger age and lower self-reported general health were significantly associated with being 'very' or 'somewhat concerned' about osteoporosis and having a 'much higher' or 'little higher' risk perception of osteoporosis and fractures. A poorer BMD result was associated with higher concern and higher risk perceptions. The presence of comorbidities, having ≥2 falls in the preceding year and maternal osteoporosis were associated with higher concern. Maternal osteoporosis, presence of comorbidities, weight loss of ≥5 kg in the preceding year and low body mass index were associated with higher perceptions of osteoporosis risk.

CONCLUSION

Women's concern and risk perception of osteoporosis and osteoporotic fractures were reasonably well founded. However, increasing age, height loss, smoking and drinking were not associated with concern and perception despite being known osteoporosis risk factors. These factors should be considered in planning for education and awareness raising programmes.

Models of care for the secondary prevention of osteoporotic fractures: a systematic review and meta-analysis

Most people presenting with incident osteoporotic fractures are neither assessed nor treated for osteoporosis to reduce their risk of further fractures, despite the availability of effective treatments. We evaluated the effectiveness of published models of care for the secondary prevention of osteoporotic fractures. We searched eight medical literature databases to identify reports published between 1996 and 2011, describing models of care for secondary fracture prevention. Information extracted from each publication included study design, patient characteristics, identification strategies, assessment and treatment initiation strategies, as well as outcome measures (rates of bone mineral density (BMD) testing, osteoporosis treatment initiation, adherence, re-fractures and cost-effectiveness). Meta-analyses of studies with valid control groups were conducted for two outcome measures: BMD testing and osteoporosis treatment initiation. Out of 574 references, 42 articles were identified as analysable. These studies were grouped into four general models of care-type A: identification, assessment and treatment of patients as part of the service; type B: similar to A, without treatment initiation; type C: alerting patients plus primary care physicians; and type D: patient education only. Meta-regressions revealed a trend towards increased BMD testing (p = 0.06) and treatment initiation (p = 0.03) with increasing intensity of intervention. One type A service with a valid control group showed a significant decrease in re-fractures. Types A and B services were cost-effective, although definition of cost-effectiveness varied between studies. Fully coordinated, intensive models of care for secondary fracture prevention are more effective in improving patient outcomes than approaches involving alerts and/or education only.

Growth and characterization of bamboo-shaped carbon nanotubes using nanocluster-assembled ZnO:Co thin films as catalyst

Bamboo-shaped carbon nanotubes (CNTs) had been successfully fabricated by a plasma enhanced chemical vapor deposition method, in which nanocluster-assembled ZnO:Co thin film was used as catalyst. It was found that bamboo-shaped CNTs were generally grown in a direction perpendicularly to the substrate surface with the tops of CNTs dominated by the droplet-like catalyst covered by the carbon layer. The diameter of CNTs was ranged from 20-50 nm. High resolution of TEM image showed that the typical CNT had a multi-walled structure with an inner core presented. The ordered graphite layers were inclined to an axis of CNT about 18 degrees and the interlayer space of a CNT was about 0.35 nm. Two peaks in Raman spectrum at 1586 cm(-1) and 1372 cm(-1) were identified as G-band and D-band for graphite, respectively. The results showed that catalyst based on ZnO:Co thin films could be used for the growth of CNTs with bamboo-shaped structure.

Does increased sunlight exposure work as a strategy to improve vitamin D status in the elderly: a cluster randomised controlled trial

SUMMARY

Sunlight exposure by improving vitamin D status could be a simple public health strategy in reducing falls among frail elder people. In a randomised controlled trial, adherence to sunlight exposure was low (median adherence, 26%) and no effect of increased UV exposure on falls risk was observed (incidence rate ratio (IRR) 1.06, P = 0.73).

INTRODUCTION

This study aimed to determine whether increased sunlight exposure was effective to improve vitamin D status and reduce falls in the elderly.

METHODS

In a cluster randomised controlled trial (NCT00322166 at ClinicalTrials.gov), 602 residents aged 70 or more (mean age, 86.4 years; 71% female) were recruited from 51 aged care facilities in Northern Sydney, Australia. Participants were randomised by facility to receive either increased sunlight exposure (additional 30-40 min/day in the early morning) with (UV+) or without (UV) calcium supplementation (600 mg/day) or neither (control) for a year. The co-primary endpoints were change in serum 25 hydroxy vitamin D (25OHD) and falls incidence after 12 months.

RESULTS

Adherence to sunlight exposure was low (median adherence, 26%; IQR, 7%-45%). Serum 25OHD levels were low at baseline (median, 32.9 nmol/L) and increased only slightly depending on the number of sunlight sessions attended over 12 months (P = 0.04). During the study, 327 falls occurred in 111 (54%) subjects in the control group, 326 falls in 111 (58%) subjects in the UV only group and 335 falls in 108 (52%) subjects in the UV+ group. By intention-to-treat analysis, there was no significant effect of increased UV exposure on falls risk (IRR, 1.06; 95% CI, 0.76-1.48; P = 0.73). However, in 66 participants who attended ≥130 sessions per year (adherence, ≥50% of 260 sessions-five per week), falls were significantly reduced (IRR, 0.52; 95% CI, 0.31-0.88; P = 0.01) compared with the control group.

CONCLUSIONS

Increased sunlight exposure did not reduce vitamin D deficiency or falls risk in frail older people. This public health strategy was not effective most likely due to poor adherence to the intervention.

Oral bisphosphonates are associated with reduced mortality in frail older people: a prospective five-year study

In a study of 2005 institutionalized older people, use of oral bisphosphonates was associated with a 27% reduction in risk of death compared to non-users after adjusting for potential confounders.

INTRODUCTION

This study investigated whether reductions in mortality reported in a trial of intravenous zoledronate after hip fracture could be seen in older people taking oral bisphosphonates.

METHODS

Two thousand and five institutionalized older people (mean age 85.7 years) were assessed at baseline and followed up for hip fracture and death for at least 5 years. Cox proportional hazards regression was used to estimate effects of bisphosphonates on risk of death.

RESULTS

At baseline, 78 subjects were taking oral bisphosphonates. Over 5 years of follow-up, 1,596 participants (80%) died. Use of bisphosphonates was associated with a 27% reduction in risk of death compared to non-users after adjusting for age, gender, type of institution, immobility, number of medications, weight, cognitive function, co-morbidities, and hip fracture incidence during the follow-up period (hazard ratio 0.73; 95% CI, 0.56 to 0.94; P = 0.02).

CONCLUSION

Oral bisphosphonates are associated with a reduction in the risk of death in the elderly. The mechanism of effect requires further investigation.

Nanostructured SmCo5 thin films with perpendicular anisotropy formed in a wide range of Sm-Co compositions

In this work, we prepared SmCo5 thin films with (0001) texture exhibiting perpendicular anisotropy in a wide range of Sm(x)Co(100-x) compositions (x = 13.2 approximately 37.0) on Cu/Ta underlayers. At a composition of Sm16.7Co83.3 (SmCo5), the SmCo5 film exhibits a maximum perpendicular coercivity of 18.2 kOe, which is attributed to a good crystallinity and an excellent (000l) texture. The SmCo5 (000l) peaks are shifted to smaller angles compared to the standard powder sample which indicates the formation of a SmCoCu alloy through Cu diffusion. The EDX result for this sample gives a composition of SmCo3Cu2.1 which confirms Cu diffusion into the SmCo5 layer. TEM image shows that SmCo5 film is well crystallized with a grain size of 50 nm.

Nanogranular L1(0) FePt-C-Ta2O5 composite media for perpendicular recording applications

In this report, the effect of simultaneously adding two dopants (C and Ta2O5) in FePt was investigated. (Fe55Pt45)79C21-(x vol%) Ta2O5 films (where x = 0% to 20%) were prepared using both low and high power magnetron sputtering on MgO (2 nm)/CrRu (30 nm) underlayers with in-situ heating at 350 degrees C. Films deposited at low power showed a decrease in exchange coupling with increasing Ta2O5 content. Out-of-plane coercivity of 7.2 kOe was observed even with up to 20 vol% Ta2O5. X-Ray diffraction spectra showed presence of FePt(001) texture for all compositions of Ta2O5 ranging from 0 to 20 vol% suggesting that the perpendicular anisotropy was maintained even with up to 20 vol% of dopant content. Films deposited at high power showed a different behavior with an initial increase in out-of-plane coercivity to 8.2 kOe and a reduction in exchange coupling with loop slope parameter (alpha) approaching a fully decoupled value of 1. Further increase in doping content led to deterioration in the out-of-plane coercivity, as well as an increase in the exchange coupling.

Interlayer exchange coupling effect of L1(0) CoPt based exchange coupled composite media

In this work, effects of exchange coupling of soft magnetic layer on switching field and magnetization reversal behaviour of CoPt-SiO2(soft)/CoPt-SiO2(hard) exchange coupled media were investigated. With increasing the thickness of the soft layer, both the coercivity and magnetization squareness of composite media decreased. Soft layer thickness 4 nm and below was more effective to significantly reduce the switching field than that above 4 nm. More incoherent switching behavior was observed with increasing soft layer thickness.

NiW/Ru underlayer for CoPt-SiO2 granular perpendicular recording media

This paper presented the usage of the NiW/Ru underlayer to replace the single Ru underlayer for promoting CoPt hcp (0002) texture. Fcc (111) textured NiW film was used to induce the Ru hcp (0002) texture. It was found that the utilization of the (111) textured NiW alloying layer promoted the formation of Ru(0002) texture, enhanced the magnetic grain isolation and generated the uniform grains with gain size less than 10 nm in CoPt-SiO2 recording layer. The out-of-plane coercivity was also enhanced with the growth of 10 nm NiW underlayer below the Ru layer.

Effects of ulinastatin and cyclophosphamide on the growth of xenograft breast cancer and expression of CXC chemokine receptor 4 and matrix metalloproteinase-9 in cancers

The aim of this study was to evaluate the effects of ulinastatin (UTI) and cyclophosphamide (CTX) as mono therapies and as combination therapy on the growth of mouse xenograft breast tumours. MCF-7 breast cancer cells were xenografted into 48 nu/nu nude mice in order to construct a breast cancer xenograft nude mouse model; mice were then untreated (control), or treated with CTX 0.1 g/kg every other day, UTI once a day at 25 000 U (low), 50 000 U (medium) or 100 000 U (high), or CTX + UTI (low), CTX + UTI (medium) or CTX + UTI (high) (n = 6 mice/group). Compared with controls, mice in each drug-treated group had a significantly reduced tumour weight, and protein and mRNA levels of CXC chemokine receptor 4 and matrix metalloproteinase-9 in both the UTI (low, medium and high doses) and CTX groups were significantly reduced, while levels in the UTI (low, medium and high doses) + CTX combination groups were significantly reduced compared with the CTX group and the UTI (low, medium, high) groups. Thus, both UTI and CTX can significantly inhibit xenograft tumours, and the UTI + CTX combination exhibited an additive effect that was superior to both CTX and UTI monotherapy.

Axonal growth from insect neurons in glia-free cultures

Mechanical dissociation of nerve and glial cells from 16-day embryos of the cockroach Periplaneta americana and their subsequent culture in a Co(2)-conditioned, chemically defined medium results in the survival of neurons but not of glial cells. The dissociated nerve cells remain alive and in excellent condition for many months and build a dense fibrillar network in presence of foregut explants from the same embryos. These explants are invaded by numerous and large fiber bundles emerging from the fibrillar network. The morphological characteristics of nerve cells and the structural and ultrastructural features of nerve bundles in long-term glia-free culture are described.

Mutation analysis of the APC gene in Taiwanese FAP families: low incidence of APC germline mutation in a distinct subgroup of FAP families

Familial adenomatous polyposis (FAP) is an autosomal-dominant disease caused by germline mutations in the adenomatous polyposis coli (APC) gene. The affected individuals develop colorectal polyposis and show various extra-colonic manifestations. In this study, we aimed to investigate the genetic and clinical characteristics of FAP in Taiwanese families and analyze the genotype-phenotype correlations. Blood samples were obtained from 66 FAP patients registered in the hereditary colorectal cancer database. Then, germline mutations in the APC genes of these 66 polyposis patients from 47 unrelated FAP families were analyzed. The germline-mutation-negative cases were analyzed by performing multiplex ligation-dependent probe amplification (MLPA) and single-strand conformation polymorphism (SSCP) analysis of the MUTYH gene. Among the analyzed families, 79% (37/47) of the families showed 28 APC mutations, including 19 frameshift mutations, 4 nonsense mutations, 3 genomic deletion mutations, 1 missense mutation, and 1 splice-site mutation. In addition, we identified 15 novel mutations in 32% (15/47) of the families. The cases in which APC mutations were not identified showed significantly lower incidence of profuse polyposis (P = 0.034) and gastroduodenal polyps (P = 0.027). Furthermore, FAP families in which some affected individuals had less than 100 polyps showed significant association with low incidence of APC germline mutations (P = 0.002). We have added the APC germline-mutation data for Taiwanese FAP patients and indicated the presence of an FAP subgroup comprising affected individuals with nonadenomatous polyps or less than 100 adenomatous polyps; this form of FAP is less frequently caused by germline mutations of the APC gene.

Selective Enrichment of Hepatocellular Cancer Stem Cells by Chemotherapy

This study investigated the enrichment of cancer stem cells (CSCs) in hepatocellular carcinoma (HCC) by chemotherapy. SMMC-7721 cells were inoculated into mice treated with 0, 2, 5 or 10 mg/kg cyclophosphamide (CTX). Tissue from the resulting tumours was re-inoculated into CTX-treated mice two more times, thus producing three generations of tumour cells for each dose of CTX. Chromosome and fluorescence-activated cell sorting analyses were performed to determine the purity of the enriched cells. Sphere culture, colony formation and proliferation assays demonstrated that the self-renewal potential, proliferative activity and clonogenicity of the enriched cells in vitro increased with increasing chemotherapy dose and generation. The ability of the enriched cells to produce xenograft tumours in mice was also dependent on chemotherapy dose and generation. In conclusion, subjecting HCC cells to chemotherapy in vivo enriched the samples for HCC CSCs in a dose-and generation-dependent manner.

Management of osteoporosis in primary care in Australia

This study reviewed factors influencing osteoporosis management in primary care settings in Australia and examined risk profiles of patients (n = 37,957) for osteoporosis. Only 29.7% of patients with a prior fracture were currently on specific medication for osteoporosis. The results highlight the need for further exploration of barriers to osteoporosis management.

INTRODUCTION

Osteoporosis management in primary care is suboptimal even for high-risk people with a history of prior fracture.

METHODS

This study reviewed factors influencing the management of individuals at risk for osteoporosis in primary care settings in Australia and examined risk profiles of patients for osteoporosis. Patients (n = 37,957, mean age 71) were recruited over a 12-month period (February 2006-Jan 2007) and interviewed.

RESULTS

With regard to risk factors for osteoporosis, 12.6% of patients reported a history of prior minimal trauma fracture, 7.5% reported a family history of osteoporosis, 7.4% reported they were current smokers, 11.4% reported low dietary calcium intake, 31.8% reported no regular weekly physical exercise and 10.3% reported current use of glucocorticoids. Of those with a prior fracture, only 29.7% were currently on specific medication for osteoporosis. Radiography (n = 17,754) demonstrated a prior vertebral fracture in 30.1%, but only 3.8% of the 17,754 patients reported current use of specific osteoporosis medication.

CONCLUSIONS

This study has confirmed low rates of treatment in primary care even in individuals who have already suffered a prior fracture or have other risk factors. This study highlights the need for further exploration of barriers to osteoporosis management in the primary care setting.

A large chest wall tumour in an asymptomatic 15-year-old girl

A 15-year-old asymptomatic girl was found to have a large left lower chest wall mass associated with chest wall invasion on an opportunistic chest radiograph. The tumour was excised and shown to be a clear cell sarcoma. Adjuvant chemotherapy was administered and she was disease free at her 10 month follow up.

Role of quantitative ultrasound to predict fracture among institutionalised older people with a history of fracture

The fracture predictive value of quantitative ultrasound (QUS) may be modified by previous fracture status. Non-significant associations between QUS parameters and fracture risk were observed among frail older people with a history of fracture. These findings suggest that QUS measurements for frail older people might be more useful in those without a fracture history.

INTRODUCTION

Quantitative ultrasound has been shown to predict risk of fracture in various populations. However, this ability may be modified by the presence of previous fracture in very frail older people.

METHODS

We assessed bone strength by QUS and clinical risk factors at baseline for 1,982 institutionalised older people. Fractures were ascertained for 2 years from baseline and validated by X-ray reports.

RESULTS

Study participants were very old (mean age = 85.7 +/- 7.1 years) and frail (70% using walking aids). Forty-five percent reported a history of fracture. During a mean follow-up period of 1.64 years, 335 participants suffered a fracture or fractures. Fracture rates were significantly higher in participants with a history of fracture compared with those without a history of fracture (16.0 vs 9.2 per 100 person years, p < 0.001). Significant associations between fracture risk and QUS parameters (broadband ultrasound attenuation and velocity of sound) were observed among participants without a history of fracture (both p < 0.01), but not among those who had a fracture history (both p >/= 0.7).

CONCLUSIONS

In very frail older people, QUS measurements may be more useful for assessing fracture risk in those without a history of fracture after age 50.

Melittin-induced [Ca2+]i increases and subsequent death in canine renal tubular cells

The effect of melittin on cytosolic free Ca2+ concentration ([Ca2+]i) and viability is largely unknown. This study examined whether melittin alters Ca2+ levels and causes Ca2+-dependent cell death in Madin-Darby canine kidney (MDCK) cells. [Ca2+]i and cell death were measured using the fluorescent dyes fura-2 and WST-1 respectively. Melittin at concentrations above 0.5 μM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 75% by removing extracellular Ca2+. The melittin-induced Ca2+ influx was also implicated by melittin-caused Mn2+ influx. After pretreatment with 1 μM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), melittin-induced Ca2+ release was inhibited; and conversely, melittin pretreatment abolished thapsigargin-induced Ca2+ release. At concentrations of 0.5–20 μM, melittin killed cells in a concentration-dependent manner. The cytotoxic effect of 0.5 μM melittin was nearly completely reversed by prechelating cytosolic Ca2+ with BAPTA. Melittin at 0.5–2 μM caused apoptosis as assessed by flow cytometry of propidium iodide staining. Collectively, in MDCK cells, melittin induced a [Ca2+]i rise by causing Ca2+ release from endoplasmic reticulum and Ca2+ influx from extracellular space. Furthermore, melittin can cause Ca2+-dependent cytotoxicity in a concentration-dependent manner.

Mismatch repair protein expression in Amsterdam II criteria-positive patients in Taiwan

BACKGROUND

Hereditary non-polyposis colorectal cancer (HNPCC) is characterized genetically by germline mutations in DNA mismatch repair (MMR) genes. Immunohistochemistry (IHC) has high sensitivity and specificity for identifying MMR-deficient tumours. This study investigated the clinical presentations and frequency of HNPCC in Taiwan by combined Amsterdam II criteria (AC-II) and IHC.

METHODS

In 1995-2003, 7108 patients with primary colorectal cancer registered in Chang Gung Memorial Hospital's Colorectal Cancer Registry were screened using AC-II. Tumour specimens were analysed for MMR protein expression by IHC, and relevant clinicopathological details were documented.

RESULTS

Some 83 patients fulfilled the AC-II. Clinicopathologically, 43 patients (52 per cent) had proximal tumours, ten (12 per cent) had poorly differentiated cancers, 17 (20 per cent) had mucinous adenocarcinoma and 51 (61 per cent) had stage I-II tumours. Seventeen patients developed second primary colonic and extracolonic cancers over a mean 7.2-year follow-up. Immunohistochemically, 58 patients were MMR protein deficient. They had a significantly earlier age of onset (P < 0.001), more proximal tumour location (P = 0.002), less advanced tumour stage (P = 0.008) and more second primary cancers (P = 0.017) compared with MMR-competent patients.

CONCLUSION

These data show significant differences in clinical features between MMR protein-deficient and MMR competent subgroups.

First Report of Soft Rot Caused by Pectobacterium carotovorum on Pinellia ternata in China

Pinellia ternata (Thumb.) Breit. (Araceae) is a traditional herb used as an antivomit, anticough, analgesic, and sedative in China for more than 1,000 years. From the summer through fall of 2003 to 2005, a high incidence (approximately 10 to 25%) of disease outbreaks characterized by water-soaked lesions and soft rot with a stinky odor were observed in the cultivated P. ternata in Shanxi Province. Water-soaked lesions were first observed on the stem base and then the plant collapsed, although the upper portion remained asymptomatic. Subsequently, the lesions expanded rapidly over the entire plant. The macerated tuber was usually reduced to a whitish, mushy, and foul-smelling pulp surrounded by undecayed periderm. A Pectobacterium species was consistently recovered from the diseased tubers on nutrient agar media. Koch's postulates were completed by stab inoculating 6-week-old peach- and willow-leaved P. ternata cultivars with the bacterial suspensions (1 × 10⁸ CFU/ml) (1). Ten control plants for each cultivar were inoculated with sterile water. After inoculation, plants were maintained in a growth chamber at 25°C with relative humidity ranging from 80 to 90%. After 2 to 3 days, typical soft rot symptoms were observed on the inoculated plants. A Pectobacterium species was reisolated from the symptomatic tubers while control plants remained healthy. This experiment was repeated in May, July, and September. The pathogenic isolates were identified as typical Pectobacterium carotovorum on the basis of morphological, physiological, and biochemical characteristics (2). The Microlog system (version 3.5; Biolog, Hayward, CA) and Sherlock Microbial Identification System (version 4.5; MIDI Newark, DE) also identified them as Pectobacterium carotovorum on the basis of similarity indices more than 66.9 and 78.2%, respectively. Their identity was then confirmed by sequencing the gene encoding the 16S rRNA (GenBank Accession No DQ785511). To our knowledge, this is the first report of Pectobacterium carotovorum as the cause of soft rot of P. ternata. References: (1) H. R. Azad et al. Plant Dis.84:973, 2000. (2) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998.

A novel amperometric biosensor based on ZnO:Co nanoclusters for biosensing glucose

ZnO:Co nanoclusters were synthesized by nanocluster-beam deposition with averaged particle size of 5 nm and porous structure, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized into the ZnO:Co nanocluster-assembled thin film through Nafion-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of the ZnO:Co nanoclusters, the constructed glucose biosensor showed a high sensitivity of 13.3 microA/mA cm2. The low detection limit was estimated to be 20 microM (S/N=3) and the apparent Michaelis-Menten constant was found to be 21 mM, indicating the high affinity of the enzyme on ZnO:Co nanoclusters to glucose. The results show that the ZnO:Co nanocluster-assembled thin films with nanoporous structure and nanocrystallites have potential applications as platforms to immobilize enzyme in biosensors.