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The study describes a novel and environment friendly route of biosynthesis of nanohydroxyapatite (nHAP). Bacillus licheniformis mediated synthesis of nHAP has been carried out with different phosphate concentrations (2%, 5%, 10% and 20% w/v) of potassium dihydrogen orthophosphate monobasic (K 2 HPO 4 ). The synthesis is supported by a two-step mechanism - (i) solubilization of P by organic acids extracellularly secreted by the bacterial strain and (ii) gelation of P and Ca. The nHAP particles were characterized using electron microscopy and XRD analysis. Powdered crystalline particles with a size range of 30 ± 5 nm were obtained with shape and size dependent on phosphate concentrations. The particles showed no adverse effect on plant growth-promoting bacteria. Evaluation of nHAP prepared by this route with 2% P source provides scope for a wide range of applications, especially as a nano-fertilizer.

Efficient delivery of DNA to cells is the primary concern to address the objective of gene therapy. Many attempts have been made to develop polymeric carriers for gene delivery. To have an efficient carrier, it is vital to understand the properties of the vector for better stability, transfection efficiency and minimal toxicity. Branched polyethylenimine (bPEI) has been considered as the 'gold standard' for gene delivery but suffers a major drawback of exhibiting high cytotoxicity. Here, we have attempted to develop a mussel-derived polymer, polydopamine (PDA), conjugated polyethylenimine nanoparticles in such a way that the toxic nature of bPEI is suppressed by the conversion of free primary amine groups to secondary and tertiary amines. Keeping the amount of PDA fixed, varying amounts of bPEIs of different molecular weights (25, 10 and 1.8kDa) were conjugated via Michael addition and/or Schiff base. A trend in hydrodynamic size of the conjugated nanoparticles was observed in the range from 160 to 300nm and zeta potential from +12-30mV in the projected three series, viz., (i) PDA 1 - 25 bPEI 0.5 , PDA 1 - 25 bPEI 1 , PDA 1 - 25 bPEI 2 ; (ii) PDA 1 - 10 bPEI 0.5 , PDA 1 - 10 bPEI 1 , PDA 1 - 10 bPEI 2 ; and (iii) PDA 1 - 1.8 bPEI 0.5 , PDA 1 - 1.8 bPEI 1 , PDA 1 - 1.8 bPEI 2 . A visible trend in the DNA condensation ability and buffering capacity was also noticed. Further, cell cytotoxicity assays revealed that pDNA complexes of PDA-bPEI nanoparticles were non-toxic to mammalian cells and these complexes exhibited several folds higher transfection efficiency than the complexes of native bPEIs as demonstrated by fluorescence measurements and flow cytometry. Altogether, the results advocate the promising potential of these conjugated nanoparticles for future in vivo applications., (Copyright © 2017 Elsevier B.V. All rights reserved.)

• Conventional urea has low nutrient use efficiency (NUE). • Integrated nutrient management (INM) with urea nanoparticles can increase NUE. • Maize-rice cropping system is used to see beneficial effects of INM. • 75% conventional urea and 25% urea nanoparticles show maximum agronomic benefits. The use of nanoparticles as plant nutrient supplementing source serves as an advanced and sustainable solution to significantly reduce the standard application dosages of conventional fertilisers while simultaneously enhancing the crop health and yield. This would lead to the overall minimization of carbon footprint generated from agriculture. Adequate supply of macronutrients like nitrogen is a key determinant for the crop productivity. Urea is the most favoured conventional nitrogen fertilizer used by farmers across the globe, however, it has low nutrient use efficiency, and more than half of the applied volume gets dissipated in the various environmental pockets. Urea nanoparticles (TNU) developed by using a precise bio-fermentation method has been evaluated in this study as a Nitrogen supplement to urea when the recommended dosage of urea is reduced by 25 and 50%. The prominent maize-rice cropping system during Kharif season of agriculture in India was investigated. Ten treatments having various combinations of conventional and nano nitrogen sources were laid out under the randomised complete block design (RCBD) in the fields of Punjab Agriculture University, India. In various treatments, TNU was applied through foliar applications and seed dressing. From the results, it was observed that the fertilising treatment having the combination of 75% dose of the conventional fertiliser in addition with TNU applications as the supplementary nitrogen source, outperformed the other treatments in terms of growth, yield and cost to benefit parameters in case of both maize and rice crops. The outcomes of the study showed that the biologically developed urea nanoparticles can safely reduce a minimum of 25% of the recommended dose of the conventional urea fertilizer, which may be introduced as a more sustainable and economical agricultural practice. [ABSTRACT FROM AUTHOR]