Progress in food packaging applications of biopolymer-nanometal composites - A comprehensive review.

Eco-friendly nanotechnology-enabled biopolymers are one of the novel concepts of packaging materials to substitute traditional synthetic polymers and their composites. This article succinctly reviews the recent developments of introducing additional functionalities to biopolymers using metal and metal oxide nanoparticles. The functionality of metal nanoparticles such as silver, zinc oxide, titanium dioxide, copper oxide, gold, and magnesium oxide, as food packaging materials were discussed. The addition of nanoparticles in biopolymers improves mechanical properties, gas barrier properties, durability, temperature stability, moisture stability, antimicrobial activity, antioxidant property, and UV absorbance and can prevent the presence of ethylene and oxygen, hence extending the shelf life of foodstuffs. Other than this, the functional activity of these biopolymer composite films helps them to act like smart or intelligent packaging. The selection of metal nanoparticles, particle migration, toxicological effect, and potential future scope in the food packaging industry are also reviewed.

A comprehensive review of multi-target directed ligands in the treatment of Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of dementia affecting specifically older population. AD is an irreversible neurodegenerative CNS disorder associated with complex pathophysiology. Presently, the USFDA has approved only four drugs viz. Donepezil, Rivastigmine, Memantine, and Galantamine for the treatment of AD. These drugs exhibit their neuroprotective effects either by inhibiting cholinesterase enzyme (ChE) or N-methyl-d-aspartate (NMDA) receptor. However, the conventional therapy "one target, one molecule" has failed to provide promising therapeutic effects due to the multifactorial nature of AD. This triggered the development of a novel strategy called Multi-Target Directed Ligand (MTDL) which involved designing one molecule that acts on multiple targets simultaneously. The present review discusses the detailed pathology involved in AD and the various MTDL design strategies bearing different heterocycles, in vitro and in vivo activities of the compounds, and their corresponding structure-activity relationships. This knowledge will allow us to identify and design more effective MTDLs for the treatment of AD.

Heterodinuclear Zn(II)-Fe(III) and Homodinuclear M(II)-M(II) [M = Zn and Ni] complexes of a Bicompartmental [N6O] ligand as synthetic mimics of the hydrolase family of enzymes.

Heterodinuclear mixed valence [Zn(II)-Fe(III)] and the homodinuclear [Zn(II)-Zn(II)] and [Ni(II)-Ni(II)] complexes of a bicompartmental ligand containing a bridging phenoxy as a O-donor and four pyridyl moieties and two amine moieties as the N-donors exhibit phosphoester hydrolysis activity similar to the hydrolase family of enzymes. While the heterodinuclear [Zn(II)-Fe(III)] (2) complex was obtained by the sequential addition of Fe(NO3)3∙9H2O and Zn(OAc)2∙2H2O to the ligand 2,6­bis{[bis(2­pyridylmethyl)amino]methyl}­4­t­butylphenol (HL) (1) in moderate yield of 37%, the homodinuclear [Zn(II)-Zn(II)] (3) and [Ni(II)-Ni(II)] (4) complexes were obtained by the direct reaction of the ligand (1) with Zn(OAc)2∙2H2O and Ni(OAc)2∙2H2O respectively, in good to moderate yields (43-63%). Based on the spectrophotometric titration and the mass spectrometry studies, a monoaquated and dihydroxo species 2C, 3C and 4C has been identified as the catalytically active species responsible for the phosphodiester hydrolysis of the bis(2,4 - dinitrophenyl)phosphate (2,4 - BDNPP) substrate in the pH range 5.5-10.5. The kinetic studies further revealed that the homodinuclear [Ni(II)-Ni(II)] complexes (4) (kcat = 1.26 × 10-2 s-1) is more active by 39 times than the homodinuclear [Zn(II)-Zn(II)] complexes (3) (kcat = 3.20 × 10-4 s-1) and 27 times more active than the heterodinuclear [Zn(II)-Fe(III)] complex (2) (kcat = 4.62 × 10-4 s-1) in the phosphodiester hydrolysis activity. Significantly enough, the catalyst-substrate adduct species (2E, 2F and 3F) containing a metal bound bis(2,4­dinitrophenyl)phosphate has been detected by mass spectrometry for the first time.

Modeling the Active Site of the Purple Acid Phosphatase Enzyme with Hetero-Dinuclear Mixed Valence M(II)-Fe(III) [M = Zn, Ni, Co, and Cu] Complexes Supported over a [N6O] Unsymmetrical Ligand.

The active site of the purple acid phosphatase enzyme has been successfully modeled by a series of hetero-dinuclear M(II)-Fe(III) [M = Zn, Ni, Co, and Cu] type complexes of an unsymmetrical [N6O] ligand that contained a bridging phenoxide moiety and one imidazoyl and three pyridyl moieties as the terminal N-binding sites. In particular, the hetero-dinuclear complexes, {L[MII(µ-OAc)2FeIII]}(ClO4)2 [M = Zn (3a), Ni (3b), Co (4a), and Cu (4b)], were obtained directly from the phenoxy-bridged ligand (HL), namely 2-{[bis(2-methylpyridyl)amino]methyl}-6-{[((1-methylimidazol-2-yl)methyl)(2-pyridylmethyl)amino]methyl}-4-t-butylphenol (2), upon sequential addition of Fe(ClO4)3·XH2O and M(ClO4)2·6H2O (M = Zn and Ni) or M(OAc)2·XH2O (M = Co and Cu), in a low-to-moderate (ca. 32-53%) yield. The temperature-dependent magnetic susceptibility measurements indicated weak antiferromagnetic coupling interactions occurring between the two metal centers in their high-spin states. All of the 3(a-b) and 4(a-b) complexes successfully carried out the hydrolysis of the bis(2,4-dinitrophenyl)phosphate (2,4-BDNPP) substrate in a mixed CH3CN/H2O (v/v 1:1) medium in the pH range of 5.5-10.5 at room temperature, thereby mimicking the functional activity of the native enzyme. The spectrophotometric titration suggested a monoaquated and dihydroxo species of the type {L[(H2O)MII(µ-OH)FeIII(OH)]}2+ to be the catalytically active species for the phosphodiester hydrolysis reaction within the pH range of ca. 5.80-7.15. Last, the kinetic studies on the hydrolysis of the model substrate, 2,4-BDNPP, divulge a Michaelis-Menten-type behavior for all complexes.