High-Throughput, Nondestructive, and Biosafe Method to Accurately Quantify Water Content in Human Fecal Samples by Benchtop 1H TD-NMR Analysis for Downstream Bioanalytical and Clinical Uses.

Water or moisture content in human stool samples is an important parameter for bioanalytical and clinical purposes. For bioanalytical use, accurate quantitation of water content in stool can provide the extent of dilution within the stool sample which can further be used for absolute quantitation of various stool based biomarkers. For clinical use, water or moisture content in stool is an important indicator of gastrointestinal health, and its accurate determination can enable quantitative assessment of the Bristol Stool Form Scale. In general, accurate determination of water content of stool samples is cumbersome, low-throughput process and is prone to harmful stool pathogens biocontamination, sample cross-contamination using techniques such as gravimetry and karl fischer titration. Here, we report a novel user-friendly high-throughput method to quantitatively and accurately measure the overall water content in human fecal samples nondestructively and biocontained in a closed tube using benchtop a 1H time domain nuclear magnetic resonance analyzer. We used gravimetry and measurement of various bile acid metabolites in stool to verify the accuracy and robustness of the water content measurement using this technique.

Combination of NMR and MRI quantitation of moisture and structure changes for convection cooking of fresh chicken meat.

This study demonstrates that a combination of bulk NMR and magnetic resonance imaging measurements of the T(2)-values of water protons can be used to determine the heat-induced changes in the structure and moisture content of fresh chicken meat which had been cooked in a convection oven at 200°C for a range of times. The gravimetric moisture content was also determined for both the raw and cooked meat. Multi-exponential fitting of the bulk NMR T(2) relaxation time data demonstrated three distinct water populations T(21) (39-43ms), T(22) (82-99ms) and T(23) (2-3ms) for raw meat which changed to 18-31ms (T(21)), 61-208ms (T(22)) and 3-7ms (T(23)) after the meat had been cooked. The T(1) and T(2) values obtained by MRI for cooked meat decreased progressively with increased heating time. There are highly significant correlations between the T(2) values from MRI and the T(21) values from bulk NMR measurements of cooked meat (r=0.986; p<0.01), and also between the normalised M(0) values from MRI and the gravimetric moisture content (r=0.953; p<0.01).

A novel non line-of-sight method for coating hydroxyapatite onto the surfaces of support materials by biomineralization.

A novel method is described for the non line-of-sight coating of hydroxyapatite onto polyurethane reticulated foam and titanium discs. This utilises a biofilm of Serratia sp. NCIMB 40259 which, when challenged with a solution containing calcium chloride and phosphatase substrate, manufactures biofilm-bound material identified as hydroxyapatite by X-ray powder diffraction analysis. Non-invasive magnetic resonance imaging was used to visualize the biofilm coating throughout the foam labyrinth and to measure the thickness of the film within reticulated foam cubes in situ. The film developed within the cube matrices was similar to that measured on the surface of a glass slide. Using LaPO(4) deposition as a model system the metallised biofilm was visualised in two-dimensional slices throughout three-dimensional images acquired by magnetic resonance imaging. A similar encrustation of hydroxyapatite on the surface of biofilm grown on titanium discs was confirmed by scanning electron microscopy. Potential applications for bio-hydroxyapatite as possible bone implant precursors are discussed.

Drug release from HPMC matrices in milk and fat-rich emulsions.

"Biorelevant" media for the fed stomach, including fat emulsions, are routinely used during in vitro testing of solid dosage forms. However, their complexity undoubtedly creates difficulties in identifying factors which affect drug release. Here, we show fats can directly influence drug release from hydroxypropyl methylcellulose (HPMC; Methocel K4M) matrices which are often subjected to biorelevant testing. Model fat systems included milk (0.1%-3.5% fat) and the parenteral emulsion Intralipid® (20%-30% fat). The matrix showed good extended-release properties for at least 12 h in these media (USP-1/USP-4), but at the highest fat concentration, release was retarded and shifted towards zero-order release. Confocal imaging studies using a water-soluble (fluorescein) and fat-soluble (Nile red) fluorophore provided evidence of phase separation of Intralipid® at the surface of the emerging gel. Combined magnetic resonance imaging-USP-4 drug release testing provided further evidence for deposition of fat on the tablets. We propose that the aqueous portion of the emulsion is removed by the hydrating matrix, causing coalescence and deposition of a fat layer at the surface, and these deposits cause slower drug release by reducing the matrix surface area available for release. Therefore, there is a risk of a direct interaction between fat emulsions and HPMC tablets, with resultant effects on drug release in vitro.

Magnetic resonance imaging of tablet dissolution.

Magnetic resonance imaging (MRI) is the technique of choice for measuring hydration, and its effects, during dissolution of tablets since it non-invasively maps (1)H nuclei associated with 'mobile' water. Although most studies have used MRI systems with high-field superconducting magnets, low-field laboratory-based instruments based on permanent magnet technology are being developed that provide key data for the formulation scientist. Incorporation of dissolution hardware, in particular the United States Pharmacopeia (USP) apparatus 4 flow-through cell, allows measurements under controlled conditions for comparison against other dissolution methods. Furthermore, simultaneous image acquisition and measurement of drug concentration allow direct comparison of the drug release throughout the hydration process. The combination of low-field MRI with USP-4 apparatus provides another tool to aid tablet formulation.