Siderophores are small organic molecules produced by microorganisms under iron-limiting conditions which enhance the uptake of iron to the microorganisms. In environment, the ferric form of iron is insoluble and inaccessible at physiological pH (7.35-7.40). Under this condition, microorganisms synthesize siderophores which have high affinity for ferric iron. These ferric iron-siderophore complexes are then transported to cytosol. In cytosol, the ferric iron gets reduced into ferrous iron and becomes accessible to microorganism. In recent times, siderophores have drawn much attention due to its potential roles in different fields. Siderophores have application in microbial ecology to enhance the growth of several unculturable microorganisms and can alter the microbial communities. In the field of agriculture, different types of siderophores promote the growth of several plant species and increase their yield by enhancing the Fe uptake to plants. Siderophores acts as a potential biocontrol agent against harmful phyto-pathogens and holds the ability to substitute hazardous pesticides. Heavy-metal-contaminated samples can be detoxified by applying siderophores, which explicate its role in bioremediation. Siderophores can detect the iron content in different environments, exhibiting its role as a biosensor. In the medical field, siderophore uses the "Trojan horse strategy" to form complexes with antibiotics and helps in the selective delivery of antibiotics to the antibiotic-resistant bacteria. Certain iron overload diseases for example sickle cell anemia can be treated with the help of siderophores. Other medical applications of siderophores include antimalarial activity, removal of transuranic elements from the body, and anticancer activity. The aim of this review is to discuss the important roles and applications of siderophores in different sectors including ecology, agriculture, bioremediation, biosensor, and medicine.

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Self-assembly of multidomain peptides (MDP) can be tailored to carry payloads that modulate the extracellular environment. Controlled release of growth factors, cytokines, and small-molecule drugs allows for unique control of in vitro and in vivo responses. In this study, we demonstrate this process of ionic cross-linking of peptides using multivalent drugs to create hydrogels for sustained long-term delivery of drugs. Using phosphate, heparin, clodronate, trypan, and suramin, we demonstrate the utility of this strategy. Although all multivalent anions result in good hydrogel formation, demonstrating the generality of this approach, suramin led to the formation of the best hydrogels per unit concentration and was studied in greater detail. Suramin ionically cross-linked MDP into a fibrous meshwork as determined by scanning and transmission electron microscopy. We measured material storage and loss modulus using rheometry and showed a distinct increase in G′ and G″ as a function of suramin concentration. Release of suramin from scaffolds was determined using UV spectroscopy and showed prolonged release over a 30 day period. Suramin bioavailability and function were demonstrated by attenuated M1 polarization of THP-1 cells compared to positive control. Overall, this design strategy has allowed for the development of a novel class of polymeric delivery vehicles with generally long-term release and, in the case of suramin, cross-linked hydrogels that can modulate cellular phenotype.

AgNPs are bona fide anticancer agents that act in a p53-dependent manner. Original submitted 16 March 2012; Revised submitted 25 August 2012; Published online 21 March 2013.

Mimicking the multistep self-assembly of the fibrillar protein collagen is an important design challenge in biomimetic supramolecular chemistry. Utilizing the complementarity of oppositely charged domains in short collagen-like peptides, we have devised a strategy for the self-assembly of these peptides into fibers. The strategy depends on the formation of a staggered triple helical species facilitated by interchain charged pairs, and is inspired by similar sticky-ended fibrillation designs applied in DNA and coiled coil fibers. We compare two classes of collagen mimetic peptides with the same composition but different domain arrangements, and show that differences in their proposed nucleation events differentiates their fibrillation capabilities. Larger nucleation domains result in rapid fiber formation and eventual precipitation or gelation while short nucleation domains leave the peptide soluble for long periods of time. For one of the fiber-forming peptides, we elucidate the packing parameters by X-ray diffraction.

Current standard of care for treating infected dental pulp, root canal therapy, retains the physical properties of the tooth to a large extent, but does not aim to rejuvenate the pulp tissue. Tissue-engineered acellular biomimetic hydrogels have great potential to facilitate the regeneration of the tissue through the recruitment of autologous stem cells. We propose the use of a dentinogenic peptide that self-assembles into β-sheet-based nanofibers that constitute a biodegradable and injectable hydrogel for support of dental pulp stem cells. The peptide backbone contains a β-sheet-forming segment and a matrix extracellular phosphoglycoprotein mimic sequence at the C-terminus. The high epitope presentation of the functional moiety in the self-assembled nanofibers may enable recapitulation of a functional niche for the survival and proliferation of autologous cells. We elucidated the hierarchical self-assembly of the peptide through biophysical techniques, including scanning electron microscopy and atomic force microscopy. The material property of the self-assembled hydrogel was probed though oscillatory rheometry, demonstrating its thixotropic nature. We also demonstrate the cytocompatibility of the hydrogel with respect to fibroblasts and dental pulp stem cells. The self-assembled peptide platform holds promise for guided dentinogenesis and it can be tailored to a variety of applications in soft tissue engineering and translational medicine in the future.

The fisheries and livestock sectors capture the highest share of protein-rich animal food and demonstrate accelerated growth as an agriculture subsidiary. Environmental pollution, climate change, as well as pathogenic invasions exert increasing stress impacts that lead the productivity momentum at a crossroads. Oxidative stress is the most common form of stress phenomenon responsible for the retardation of productivity in fisheries and livestock. Essential micronutrients play a determinant role in combating oxidative stress. Selenium, one of the essential micronutrients, appears as a potent antioxidant with reduced toxicity in its nanoscale form. In the present review, different methods of synthesis and characterization of nanoscale selenium have been discussed. The functional characterization of nano-selenium in terms of its effect on growth patterns, feed digestibility, and reproductive system has been discussed to elucidate the mechanism of action. Moreover, its anti-carcinogenic and antioxidant potentiality, antimicrobial and immunomodulatory efficacy, and fatty acid reduction in liver have been deciphered as the new phenomena of nano-selenium application. Biologically synthesized nano-selenium raises hope for pharmacologically enriched, naturally stable nanoscale selenium with high ecological viability. Hence, nano-selenium can be administered with commercial feeds for improvising stress resilience and productivity of fish and livestock.

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