Natural and polyanionic heparin polysaccharide functionalized upconversion nanoparticles for highly sensitive and selective ratiometric detection of pesticide.

Pesticide contamination is a global concern, threatening human health and food safety. Herein, we developed heparin (HEP) functionalized upconversion nanoparticles (UCNPs)-based ratiometric nanosensor for the sensitive detection of 2,6-dichloro-4-nitroaniline (DCN) pesticide via inner filter effect. The strategy for HEP functionalization of UCNPs is based on adjusting the surface potentials of UCNPs with polyanionic HEP through the electrostatic interaction. UCNPs (NaYbF4:Gd/Y/Tm@NaYbF4@NaYF4) was designed with core-shell-shell structure and extra sensitizer layer for efficient and strong upconversion luminescence (UCL) in the range of UV to NIR. After incorporation of DCN, the upconverted UV emission of UCNPs-HEP ratiometric nanosensor was considerably quenched with the NIR UCL at 800 nm remaining unchanged as internal standard. The UCNPs-HEP ratiometric nanosensor can achieve outstandingly selective and sensitive detection of DCN at the wide linear range of 5-300 µM with a detection limit of 0.41 µM. The remarkable applicability of the UCNPs-HEP ratiometric nanosensor was verified in apple, cucumber and grapes samples. The developed UCNPs-HEP ratiometric nanosensor with excellent biocompatibility and water dispersion capability, is promising for convenient, selective and sensitive sensing of DCN towards food and aqueous samples.

Visible-light excitable Eu3+-induced hyaluronic acid-chitosan aggregates with heterocyclic ligands for sensitive and fast recognition of hazardous ions.

Water-soluble luminescent lanthanide complexes that can be excited with visible light could enable rapid detection of toxic anions and cations in biological systems. Eu3+-induced hyaluronic acid-chitosan aggregates (EIHCA) can improve the stability, biocompatibility, efficiency, and light absorption of luminescent Eu3+ complexes. Visible-range excitation may avoid phototoxicity associated with overexposure to UV light in biological and ecological applications. In this work, we synthesized and characterized series of EIHCA complexes having three N-donor heterocyclic ligands: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Dphen), 2,2': 6',2″-terpyridine (Tpy) and 1,10-phenanthroline monohydrate (Phen). These complexes possessed bright red fluorescence with a visible range excitation maximum. The photophysical properties of one formulation (we denote as EDL6) include fast quenching response (20 s) of the fluorescence, multi-selectivity, low limit of detection, and high quenching (Ksv) values, enabling selective, rapid and sensitive recognition of Cr2O72- and Fe3+ in aqueous solution. Furthermore, EDL6 exhibits cytocompatibility with mammalian cells that make these complexes promising biocompatible candidate as a safe replacement of organic fluorophores for fluorescence sensing applications. Thus, these new EIHCA complexes were successfully employed for the selective detection of hazardous materials in biological and aqueous environment samples.

Selective Sensing of Cu2+ and Fe3+ Ions with Vis-Excitation using Fluorescent Eu3+-Induced Aggregates of Polysaccharides (EIAP) in Mammalian Cells and Aqueous Systems.

Fluorescent lanthanide complexes have favorable features for fluorescence-based sensors compared to organic fluorophores and quantum dots. They exhibit very long fluorescence lifetimes, sharp emission bands, and stability with respect to photo-bleaching, without blinking. However, these complexes are usually hydrophobic, and many are excited by UV light, making them hazardous and incompatible with aqueous environments and biological samples. In this work, the strong fluorescent Eu3+-induced aggregates of polysaccharides (EIAP) was used to improve their aqueous solubility, and to tune the appropriate excitation wavelength in the visible range for avoiding toxicity of UV light in biological applications. The complexes exhibit bright fluorescence with an excitation maximum in the visible range, near 405 nm. EIAP 3 also exhibit rapid quenching response in the presence of transition metal ions. This enables the detection of Cu2+ and Fe3+ below 1 ppm. The reverse of quenching response of copper by the addition of a chelating agent makes it possible to recover the fluorescence property. Successfully, the EIAP exhibit cytocompatibility with mammalian cells. Thus, these new polysaccharide-based complexes have the potential for rapid, sensitive and selective metal ion sensors for the environmental systems.

Amino acids loaded chitosan/collagen based new membranes stimulate angiogenesis in chorioallantoic membrane assay.

Chitosan/collagen-based hydrogels were studied for their promising role in skin tissue engineering applications due to their unique biocompatibility and biodegradation properties. Amino acids are not only the mean of protein building units but also support endothelial cells proliferation and trigger angiogenesis during wound healing. The purpose of this study was to prepare amino acid based pro-angiogenic materials. Three structurally closed amino acids (AA) (arginine, alanine and phenylalanine) were loaded into chitosan/collagen hydrogels (ACC hydrogels) to study their effect on angiogenesis. In this study the ACC hydrogels were prepared through freeze drying procedure and their angiogenic potential was studied by chorioallantoic membrane assay (CAM assay). FTIR analysis was performed to confirm that there was no chemical change took place in polymeric materials during synthesis procedures. Results revealed that, arginine-loaded hydrogels were the most porous, with more interconnected pores and also the maximum growth of blood vessels were found around and inside the arginine loaded scaffold. The qualitative analysis for blood vessels showed the significant difference between control, chitosan/collagen alanine loaded hydrogel (CH-Ala), chitosan/collagen phenylalanine loaded hydrogel (CH-Phe) and chitosan/collagen arginine loaded hydrogel (CH-Arg) materials. Among these studied materials the CH-Arg was found more capable for angiogenesis.

Development of K-doped ZnO nanoparticles encapsulated crosslinked chitosan based new membranes to stimulate angiogenesis in tissue engineered skin grafts.

Nanoparticles are well recognized for their biological applications including tissue-regeneration due to large surface area and chemical properties. In this study, K-doped zinc oxide (ZnO) nanoparticles containing porous hydrogels were synthesized via freeze gelation. The morphology and pore dimensions were studied by scanning electron microscopy (SEM). The chemical structural analysis of the synthesized hydrogels was investigated by Fourier Transform Infrared (FTIR) spectroscopy. In swelling studies, material containing ZnO nanoparticles with 2% potassium dopant concentration CLH-K2.0) showed greater degree of swelling as compared to all other materials. The degradation studied was tested in three different degradation media, i.e. phosphate buffer saline (PBS), lysozyme and hydrogen peroxide and relatively higher degradation was seen in hydrogen peroxide. The synthesized hydrogels were implanted on the chick chorioallantoic membrane (CAM) to investigate their angiogenic potential. The CLH-K2.0 hydrogel stimulated angiogenesis greater than all other materials; blood vessels were attached and grown inside this scaffold, showing its strong angiogenic potential.