Browsing by Author "John A, A"

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    An aqueous method for the controlled manganese (Mn2+) substitution in superparamagnetic iron oxide nanoparticle for contrast enhancement in MRI
    (Physical Chemistry Chemical Physics., 2015-01) Beerana, AE; Nazeerb, SS; Fernandezc, FB; Muvvala, KS; Wunderlich, W; Anil, S; Vellappally, S; Rao, R; John A, A; Jayasree, RS; Varma, HK
    Despite the success in the use of superparamagnetic iron oxide nanoparticles (SPION) for various scientific applications, its potential in biomedical fields has not been exploited to its full potential. In this context, an in situ substitution of Mn2+ was performed in SPION and a series of ferrite particles, MnxFe1−xFe2O4 with a varying molar ratio of Mn2+ : Fe2+ where ‘x’ varies from 0–0.75. The ferrite particles obtained were further studied in MRI contrast applications and showed appreciable enhancement in their MRI contrast properties. Manganese substituted ferrite nanocrystals (MnIOs) were synthesized using a novel, one-step aqueous co-precipitation method based on the use of a combination of sodium hydroxide and trisodium citrate (TSC). This approach yielded the formation of highly crystalline, superparamagnetic MnIOs with good control over their size and bivalent Mn ion crystal substitution. The presence of a TSC hydrophilic layer on the surface facilitated easy dispersion of the materials in an aqueous media. Primary characterizations such as structural, chemical and magnetic properties demonstrated the successful formation of manganese substituted ferrite. More significantly, the MRI relaxivity of the MnIOs improved fourfold when compared to SPION crystals imparting high potential for use as an MRI contrast agent. Further, the cytocompatibility and blood compatibility evaluations demonstrated excellent cell morphological integrity even at high concentrations of nanoparticles supporting the non-toxic nature of nanoparticles. These results open new horizons for the design of biocompatible water dispersible ferrite nanoparticles with good relaxivity properties via a versatile and easily scalable co-precipitation route.
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    Injectable selfcrosslinking hydrogels for meniscal repair: A study with oxidized alginate and gelatin
    (Carbohydrate Polymers, 2020-05) Resmi, R; Parvathy, J; John A, A; Joseph, R
    Injectable in situ gelling hydrogels are viable treatment options for meniscal injuries occurring in athletes. The present study aims to develop an injectable hydrogel via borax complexation of oxidized alginate, followed by a self-crosslinking reaction with gelatin through a Schiff’s base reaction. Gelation kinetics and degree of crosslinking could be controlled by changing the concentration of components and the formation of Schiff ;'s base formation was confirmed by Raman spectroscopy. The injectable alginate dialdehyde-gelatin (15ADA20G) hydrogel showed 423 ± 20 % water uptake, had an average pore size of 48 μm and compressive strength 295 ± 32 kPa. Phase contrast images, scanning electron micrographs and actin staining depicted adhesion, profuse proliferation, and distribution of fibrochondrocytes on the hydrogel demonstrating its cytocompatibility. Application of hydrogel at the pig meniscal tear ex vivo showed good integration with the host meniscal tissue. Further, the histology of 15ADA20G hydrogel filled meniscus showed retention of hydrogel in the close proximity of meniscal tear even after 3days in culture. The self-crosslinking injectable hydrogel offers a niche for the growth of fibrochondrocytes.