Colorimetric assay for the determination of molecular weight distribution and branching characteristics of starch hydrolysates.

Here, we present a gold nanoparticle-based colorimetric assay for the determination of molecular weight distribution and branching characteristics of enzymatically hydrolyzed starch. The steric stabilization effect of starch hydrolysate on the colloidal stability of AuNPs was found to be proportional to the ratio of high molecular weight amylopectins, which was clearly reflected by the intensity of the characteristic surface plasmonic resonance (SPR) absorbance peak of the AuNPs. The fractional change of high molecular weight amylopectin over the course of enzymatic hydrolysis reaction could be measured based on the intensity of SPR peak, in which the results correlated well with those obtained by conventional gel permeation chromatography. With the proper calibration of a specific set of enzyme and starch type, this method would provide a fairly simple and fast means of analyzing the molecular weight distribution of starch hydrolysate on site as well as the amylose content in native starch.

Charge-switchable magnetic separation and characterization of food additive titanium dioxide nanoparticles from commercial food.

Growing concerns about the potential health effects of nanoscale titanium dioxide (TiO2) have necessitated the need for monitoring the size distribution and physicochemical properties of food additive TiO2 that are present in commercial food. Acid digestion is by far the most widely used method to remove interfering food matrices, but the highly corrosive nature of the reaction could alter the physicochemical properties of the TiO2, which may give a skewed information about the materials. Here, we report an effective approach to extract intact form of food additive TiO2 nanoparticles from processed food through charge-charge interaction between TiO2 particles and charge-switchable starch magnetic beads (PL@SMBs), of which the captured TiO2 is readily harvested by switching the surface charge of PL@SMBs to neutral. The size and surface property of extracted TiO2 were shown to be well maintained due to the mild nature of the reaction. The extracted TiO2 particles from 10 commercial processed food showed a size distribution from 40 to 250 nm with a mean diameter of 115 nm, of which 22 % of them were less than 100 nm. The extracted TiO2 did not exhibit short-term cytotoxicity, but induced cellular oxidative stress at high concentration.

Paper-Based Radial Chromatographic Immunoassay for the Detection of Pathogenic Bacteria in Milk.

Here, a paper-based radial flow chromatographic immunoassay (RFCI) employing gold nanoparticles (AuNPs) as chromatic agents was developed for the detection of Escherichia coli O157:H7 in whole milk. A 4-repeated gold-binding peptide-tagged (4GBP) streptococcal protein G (SPG) fusion protein was constructed as a bifunctional linker to immobilize antibodies on the surface of AuNPs with a well-oriented form based on the specific affinity of GBP and SPG to the gold and Fc portion of the antibody, respectively. 4GS@AuNPs prepared with the bifunctional linker protein exhibited excellent colloidal stability even at high salt concentrations of up to 500 mM, which is a critical requirement for its application to a broad range of biological and food samples. The enhanced colloidal stability and excellent binding capability of the immuno-4GS@AuNPs toward target bacteria lowered the detection limit of RFCI for target pathogenic bacteria in whole milk as low as 103 CFU/mL, which is by an order of magnitude lower than that of conventional immuno-AuNPs prepared with physical adsorption of antibodies. The RFCI pattern could also be converted into a grayscale value by simple image processing for quantitative determination of target pathogenic bacteria. This paper-based detection system would provide an effective means of monitoring the presence of food-borne pathogens in real food samples with naked eyes.

Korean version of the delirium rating scale-revised-98: reliability and validity.

OBJECTIVE: The aims of the present study were 1) to standardize the validity and reliability of the Korean version of Delirium Rating Scale-Revised-98 (DRS-R98-K) and 2) to establish the optimum cut-off value, sensitivity, and specificity for discriminating delirium from other non-delirious psychiatric conditions. METHODS: Using DSM-IV criteria, 157 subjects (69 delirium, 29 dementia, 32 schizophrenia, and 27 other psychiatric patients) were enrolled. Subjects were evaluated using DRS-R98-K, DRS-K, Mini-Mental State Examination (MMSE-K), and Clinical Global Impression-Severity (CGI-S) scale. RESULTS: DRS-R98-K total and severity scores showed high correlations with DRS-K. They were significantly different across all groups (p=0.000). However, neither MMSE-K nor CGI-S distinguished delirium from dementia. All DRS-R98-K diagnostic items (#14-16) and items #1 and 2 significantly discriminated delirium from dementia. Cronbach's alpha coefficient revealed high internal consistency for DRS-R98-K total (r=0.91) and severity (r=0.89) scales. Interrater reliability (ICC between 0.96 and 1) was very high. Using receiver operating characteristic analysis, the area under the curve of DRS-R98-K total score was 0.948 between the delirium group and all other groups and 0.873 between the delirium and dementia groups. The best cut-off scores in DRS-R98-K total score were 18.5 and 19.5 between the delirium and the other three groups and 20.5 between the delirium and dementia groups. CONCLUSION: We demonstrated that DRS-R98-K is a valid and reliable instrument for assessing delirium severity and diagnosis and discriminating delirium from dementia and other psychiatric disorders in Korean patients.