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Biomedical subjects

Arvind Sinha

Publications and source records attributed to Arvind Sinha.

15 recordsLinked to original sources
PubMed2006

Synthesis and sintering of biomimetic hydroxyapatite nanoparticles for biomedical applications.

Synthesis of monodisperse nanoparticles with uniform morphology and narrow size distribution as achieved by nature is a challenge to materials scientists. Mimicking the process of biomineralization has led to the development of biomolecules mediated synthesis of nanoparticles that overcomes many of the problems associated with nanoparticle synthesis. Termed as biomimetics this paradigm shift in the philosophy of synthesis of materials is very advantageous for the design-based synthesis of nanoparticles. The effect of concentration of a protein named bovine serum albumin on particle size, morphology and degree of crystallinity of biomimetically synthesized hydroxyapatite particles, has been studied. Results establish 0.5% protein as the required concentration to produce 30-40 nm sized hydroxyapatite particles with an optimum degree of crystallinity as required for biomedical applications. These particles synthesized under certain stringent conditions are found to have stoichiometric calcium:phosphorus ratio of 1.67 and exhibit restricted grain growth during sintering.

Biomimetic Materials↗
PubMed2006

Hydroxyapatite coating on stainless steel pre-coated with bovine serum albumin at ambient conditions.

A biomimetic process for coating of nanosized hydroxyapatite on stainless steel, which capitalises the dual nature of the protein bovine serum albumin in both metal binding and a strong affinity for calcium ions, has been developed. The novelty of the process lies in pre-conditioning the metallic surface using the above protein prior to its mineralization with hydroxyapatite at ambient conditions. The microporous morphology of these coatings may provide favourable solubility and resorbability as desired by many orthopaedic and orthodontic applications.

Animals↗
PubMed2005

Magnetic field induced synthesis and self-assembly of super paramagnetic particles in a protein matrix.

Aqueous solution of a globular protein named bovine serum albumin was homogeneously mixed with ferrous and ferric ions and allowed to gel at ambient conditions. Gels were then oxidized using sodium hydroxide, in the presence of magnetic field of magnitude 0.13 T. The effect of magnetic field on the above biomimetic synthesis was a reduction in particle size and a directional assembly of synthesized super paramagnetic particles into a regular pattern in the protein film. The microstructural revelation was complimentary to Mossbauer results and magnetic measurement studies, i.e., an interesting variation in the magnetic behaviour of self-assembled super paramagnetic particles as a function of dc magnetic field induced ordering.

Biomimetic Materials↗
PubMed2004

Systematic evolution of a porous hydroxyapatite-poly(vinylalcohol)-gelatin composite.

Hydroxyapatite (HAp)-poly(vinylalcohol) (PVA)-gelatin nanocomposite was biomimetically synthesized and characterized. Fourier transform infrared spectroscopy (FT-IR) analysis of hydroxyapatite, hydroxyapatite-poly(vinylalcohol) and hydroxyapatite-poly(vinylalcohol)-gelatin composites show modification of hydroxyl, amide and phosphate bands as a result of chemical interaction of hydroxyapatite with the above composite matrices. Transmission electron microscopy (TEM) confirmed the time-dependent development of a porous structure of hydroxyapatite-poly(vinylalcohol)-gelatin as a consequence of nucleation at the HAp aggregate-matrix interface. A literature survey holds great promise for the above as scaffolds in terms of increased mechanical properties and bioactivity.

Biocompatible Materials↗
PubMed2004

Acute appendicitis complicating Mitrofanoff procedure.

The Mitrofanoff urinary diversion is fraught with the complication of cutaneous stomal stenosis, which prevents catheterization. The authors report another sequel of stomal stenosis-acute appendicitis, a complication not reported hitherto.

Anal Canal↗
PubMed2003

Correction for oral contrast artifacts in CT attenuation-corrected PET images obtained by combined PET/CT.

UNLABELLED: Recent studies have shown increased artifacts in CT attenuation-corrected (CTAC) PET images acquired with oral contrast agents because of misclassification of contrast as bone. We have developed an algorithm, segmented contrast correction (SCC), to properly transform CT numbers in the contrast regions from CT energies (40-140 keV) to PET energy at 511 keV. METHODS: A bilinear transformation, equivalent to that supplied by the PET/CT scanner manufacturer, for the conversion of linear attenuation coefficients of normal tissues from CT to PET energies was optimized for BaSO(4) contrast agent. This transformation was validated by comparison with the linear attenuation coefficients measured for BaSO(4) at concentrations ranging from 0% to 80% at 511 keV for PET transmission images acquired with (68)Ge rod sources. In the CT images, the contrast regions were contoured to exclude bony structures and then segmented on the basis of a minimum threshold CT number (300 Hounsfield units). The CT number in each pixel identified with contrast was transformed into the corresponding effective bone CT number to produce the correct attenuation coefficient when the data were translated by the manufacturer software into PET energy during the process of CT attenuation correction. CT images were then used for attenuation correction of PET emission data. The algorithm was validated with a phantom in which a lesion was simulated within a volume of BaSO(4) contrast and in the presence of a human vertebral bony structure. Regions of interest in the lesion, bone, and contrast on emission PET images reconstructed with and without the SCC algorithm were analyzed. The results were compared with those for images obtained with (68)Ge-based transmission attenuation-corrected PET. RESULTS: The SCC algorithm was able to correct for contrast artifacts in CTAC PET images. In the phantom studies, the use of SCC resulted in an approximate 32% reduction in the apparent activity concentration in the lesion compared with data obtained from PET images without SCC and a <7.6% reduction compared with data obtained from (68)Ge-based attenuation-corrected PET images. In one clinical study, maximum standardized uptake value (SUV(max)) measurements for the lesion, bladder, and bowel were, respectively, 14.52, 13.63, and 13.34 g/mL in CTAC PET images, 59.45, 26.71, and 37.22 g/mL in (68)Ge-based attenuation-corrected PET images, and 11.05, 6.66, and 6.33 g/mL in CTAC PET images with SCC. CONCLUSION: Correction of oral contrast artifacts in PET images obtained by combined PET/CT yielded more accurate quantitation of the lesion and other, normal structures. The algorithm was tested in a clinical case, in which SUV(max) measurements showed discrepancies of 2%, 1.3%, and 5% between (68)Ge-based attenuation-corrected PET images and CTAC PET images with SCC for the lesion, bladder, and bowel, respectively. These values correspond to 6.5%, 62%, and 66% differences between CTAC-based measurements and (68)Ge-based ones.

Administration, Oral↗
PubMed2002

Enterolithiasis with imperforate anus: report of a case.

A three-year-old child presented with imperforate anus. A local perineal procedure was performed at birth, possibly without repairing the fistula. The child later presented with severe anal stenosis, which required a divided sigmoid colostomy. The child later presented at the age of two years with multiple radio-opaque shadows in the pelvis. These proved to be enteroliths, which had developed in the distal rectal stump possibly due to a large associated recto-urethral fistula with associated urinary stasis.

Anus, Imperforate↗
PubMed2002

Two orifices in the perineum of a girl with imperforate anus: possibility of uterovaginal agenesis associated with rectovestibular fistula.

The authors describe 4 cases of rectovestibular fistula associated with uterovaginal atresia. The diagnosis of the associated uterovaginal atresia was missed in the neonatal period in all 4. It was diagnosed in 2 cases at puberty while investigating for amenorrhea; the other 2 were discovered during the repair of anorectal malformation in early childhood. A variety of techniques were used successfully for vaginal reconstruction. The authors believe that the incidence of such an association is very similar to that of imperforate anus with rectovaginal fistula and therefore suggest that if there are 2 orifices in the perineum of a girl with imperforate anus, it could be either a rectovaginal fistula or a rectovestibular fistula with uterovaginal agenesis. They recommend that all such neonates have an endoscopy or a magnetic resonance imaging done to distinguish between the 2 conditions. This distinction is of importance because the latter would require a concomitant vaginal reconstruction procedure along with anorectoplasty.

Abnormalities, Multiple↗
PubMed2002

'High' anorectal malformation in boys: need for clarity of definition and management.

Posterior sagittal anorectoplasty is purported to be the approach of choice for the treatment of both intermediate and high variety of anorectal malformations. The authors describe their devastating experiences with 2 cases of high variety of anorectal malformations in which defects were repaired thorough the posterior sagittal approach. In the first case, because of the high level of the rectal pouch, complete urethrovesical disconnection was done along with inadvertent mobilization and pull-through of urinary bladder. The patient subsequently required major reconstructive procedures. In another case, the bladder was partially mobilized before the mistake was realized; the high-lying rectum was later identified, and a pull-through was performed without any ill consequences. The authors infer that only the patients with rectal pouches ending caudal to the third sacral vertebra should have their definitive surgery performed through posterior sagittal approach. They suggest that PS3 line should be the watershed in management of anorectal malformation in boys.

Anal Canal↗