Glucosamine to gold nanoparticles binding studied using Raman spectroscopy

The binding of glucosamine to gold in water solutions of glucosamine hydrochloride mixed with clean colloidal gold nanoparticles obtained by laser ablation in liquid was studied using surface-enhanced Raman scattering (SERS), dynamic light scattering (DLS) and UV–VIS spectroscopy. The purpose of this study was to establish whether the binding of charged aminogroup to gold nanoparticles (AuNPs) is taking place, and if it does, how can it be identified by means of SERS. The average size of dried gold nanoparticles was (20 ± 4) nm determined by averaging the sizes observed in transmission electron microscopy micrographs, which is smaller than the average size of gold nanoparticles in water solution as determined by DLS: (52 ± 2) nm. Upon adding the glucosamine solutions to gold colloid, average hydrodynamic diameter of ions was slightly larger for 0.1 mM glucosamine solution (55 ± 2 nm), while it increased to (105 ± 22) nm in the case of 1 mM solution, and was (398 ± 54) nm when 10 mM glucosamine solution was added. Most prominent Raman bands observed both for 0.1 mM and 1 mM glucosamine solutions were located at 1165 cm−1, 1532 and 1586 cm−1 and assigned to C-N coupled with C-C stretching, and C-NH3+ deformation angles bending. In SERS spectrum of 1 mM GlcN+ solution, two strong bands at 999 and 1075 cm−1 were found and attributed to C-Oring stretching coupled with C-NH3+ bending (999 cm−1) and to dominantly C-O stretching vibration. The differences in SERS spectra are attributed to different number of glucosamine molecules that attach to gold nanoparticles and their orientation with respect to the metal particle surface, partly due to presence of beta anomers protonated at anomeric oxygen position. The assignment of glucosamine bands was further corroborated by comparison with vibrational spectra of alpha and beta glucose and of polycrystalline powder of glucosamine hydrochloride. For all three substances comprehensive calculation of vibrational density of states was conducted using density functional theory. Benchmark bands for polycrystalline glucose anomers distinction are 846 and 915 cm−1 for alpha glucose, and 902 cm−1 for beta glucose. However, the bands observed in SERS spectra of 0.1 mM glucosamine solution at 831, 899, and 946 cm−1 or in 1 mM solution at 934 cm−1 cannot be easily identified as belonging either to alpha or beta glucosamine anomer, due to complexity of atomic motions involved. The identification of vibrational bands associated with –CNH3+ group will aid SERS studies on amino acids, especially in cases when several atomic groups could possibly bind to AuNPs

Characterization of new cocrystals by raman spectroscopy, powder X-ray diffraction, differential scanning calorimetry, and transmission raman spectroscopy

Cocrystals have been increasingly recognized as an attractive alternative delivery form for solids of drug products. In this work, salicylic acid was employed as a cocrystal former with the nicotinic acid, dl-phenylalanine, and 6-hydroxynicotinic acid (6HNA). Also, 3,4-dihydroxybenzoic acid with oxalic acid was studied. The cocrystals in all cases were prepared by slow evaporation from ethanol followed by characterization using Raman spectroscopy, powder X-ray diffraction, transmission Raman spectroscopy (TRS), and differential scanning calorimetry. Full understanding of the effects of formation on the vibrational modes of motion was obtained by the complete assignment of the spectra of the starting materials and of the cocrystal components. The results show that all the cocrystals, prepared in a 1:1 molar ratio, possess unique thermal, spectroscopic, and X-ray diffraction properties. Raman and TRS spectra showed that the vibrational modes of the cocrystal were different from those of the starting materials, suggesting that Raman spectroscopy and TRS are effective tools to evaluate cocrystal formation through interaction of their components. In addition, we have used a synthetic standard containing a 1:1:1 mixture of KNO 3 and raw material for which each sample was analyzed at seven random positions, with each point sampled twice. We have done the same with all cocrystals (1:1 KNO 3 and cocrystal), the ratios confirming that the cocrystal components (were in a 1:1 molar ratio). © 2010 American Chemical Society

Cholesterol, diastolic blood pressure, and stroke: 13,000 strokes in 450,000 people in 45 prospective cohorts. Prospective studies collaboration.

Individual studies of stroke have not clearly answered two questions: on the relation, if any, between total blood cholesterol and stroke; and on how the strength of the relation between diastolic blood pressure and stroke varies with age. The associations of blood cholesterol and diastolic blood pressure with subsequent stroke rates were investigated by review of 45 prospective observational cohorts involving 450,000 individuals with 5-30 years of follow-up (mean 16 years, total 7.3 million person-years of observation), during which 13,397 participants were recorded as having had a stroke. Most of these were fatal strokes in studies that recorded only mortality and not incidence, but about one-quarter were from studies that recorded both fatal and non-fatal strokes. After standardization for age, there was no association between blood cholesterol and stroke except, perhaps, in those under 45 years of age when screened. This lack of association was not influenced by adjustment for sex, diastolic blood pressure, history of coronary disease, or ethnicity (Asian or non-Asian). However, because the types of the strokes were not centrally available, the lack of any overall relation might conceal a positive association with ischaemic stroke together with a negative association with haemorrhagic stroke. When the highest and the lowest of the six blood pressure categories were compared, the difference in usual diastolic blood pressure was 27 mm Hg (102 vs 75 mm Hg), and there was a fivefold difference in stroke risk. This fivefold difference was seen both in those with a pre-existing history of coronary heart disease and in those without it. The proportional difference in stroke risk, however, was more extreme in middle than in old age. Among those aged < 45, 45-64, and 65+ when screened, the differences in the relative risks of stroke (between the highest diastolic blood pressure category and a combination of the lowest two categories) were tenfold, fivefold, and twofold, respectively. However, because the absolute stroke risks are greater in old age, the absolute differences in the annual stroke rates showed an opposite pattern, being 2, 5, and 8 per thousand, respectively. This suggests that the effects of therapeutic blood pressure reductions should be assessed separately in middle age and in old age

Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study

International audienceThe variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a ‘primary’ setup and the test data are generated on ‘replicate’ setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies