Fluorescence enhancement of glutathione capped CdTe/ZnS quantum dots by embedding into cationic starch for sensitive detection of rifampicin.

In this study, we describe the synthesis of a new quantum dots (QDs) by embedding glutathione capped CdTe/ZnS QDs into cationic starch biopolymer (CS-GSH-CdTe/ZnS QDs). The fluorescence intensity of prepared QDs was significantly enhanced. When QDs interacted with rifampicin, the fluorescence intensity of the CS-GSH-CdTe/ZnS QDs was highly quenched compared with GSH-CdTe/ZnS QDs. Based on the above, a new fluorescent nanosensor for simple, sensitive and selective detection of rifampicin was developed. The fluorescence quenching was well described by the typical Stern-Volmer equation. After optimization, the linear range of the as-prepared QDs fluorescence intensity versus the concentration of rifampicin was F0/F=0.0422Q+1.109 (R2=0.99). The detection limit was 0.06×10-6mol/L. The proposed method with satisfactory results was used to detect rifampicin in commercial capsules and tablets.

Synthesis of a novel thermo/pH sensitive nanogel based on salep modified graphene oxide for drug release.

Nanogels (NGs) are three-dimensional water soluble cross-linked hydrogel materials in the nanoscale size range with a high loading capacity for guest molecules and act as drug carrier systems. In the present work, a new type of thermo/pH sensitive NG comprising salep modified graphene oxide (SMGO) with branched N-isopropylacrylamide (NIPAM) and acrylic acid (AA) was prepared. The SMGO/P(NIPAM-co-AA) NGs exhibited nanoporous structure and spherical particles with diameters about 82nm as characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The samples were also characterized by Fourier transform infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TGA) to further confirm about the formation of NGs. Doxorubicin (DOX) loaded SMGO/P(NIPAM-co-AA) NGs showed thermo/pH dependent releasing behavior: slow drug release at neutral pH and lower temperature but increased significantly in acidic pH and higher temperature, without any burst release. In addition, the NGs exhibited no effect on the cell viability in the tested concentration range up to 410µg/mL and drug release systems enhanced toxicity to HeLa cells when compared to the equivalent dose of the free drug. Overall, our results put forth NGs as potential candidates in the development of a new nanocarrier for anti-cancer drug delivery.

Probing the interaction of a new synthesized CdTe quantum dots with human serum albumin and bovine serum albumin by spectroscopic methods.

A novel CdTe quantum dots (QDs) were prepared in aqueous phase via a facile method. At first, poly (acrylic amide) grafted onto sodium alginate (PAAm-g-SA) were successfully synthesized and then TGA capped CdTe QDs (CdTe-TGA QDs) were embed into it. The prepared CdTe-PAAm-g-SA QDs were optimized and characterized by transmission electron microscopy (TEM), thermo-gravimetric (TG) analysis, Fourier transform infrared (FT-IR), UV-vis and fluorescence spectroscopy. The characterization results indicated that CdTe-TGA QDs, with particles size of 2.90 nm, were uniformly dispersed on the chains of PAAm-g-SA biopolymer. CdTe-PAAm-g-SA QDs also exhibited excellent UV-vis absorption and high fluorescence intensity. To explore biological behavior of CdTe-PAAm-g-SA QDs, the interactions between CdTe-PAAm-g-SA QDs and human serum albumin (HSA) (or bovine serum albumin (BSA)) were investigated by cyclic voltammetry, FT-IR, UV-vis, and fluorescence spectroscopic. The results confirmed the formation of CdTe-PAAm-g-SA QDs-HSA (or BSA) complex with high binding affinities. The thermodynamic parameters (ΔG<0, ΔH<0 and ΔS<0) were indicated that binding reaction was spontaneous and van der Waals interactions and hydrogen-bond interactions played a major role in stabilizing the CdTe-PAAm-g-SA QDs-HSA (or BSA) complexes. The binding distance between CdTe-PAAm-g-SA QDs and HSA (or BSA)) was calculated about 1.37 nm and 1.27 nm, respectively, according to Forster non-radiative energy transfer theory (FRET). Analyzing FT-IR spectra showed that the formation of QDs-HSA and QDs-BSA complexes led to conformational changes of the HSA and BSA proteins. All these experimental results clarified the effective transportation and elimination of CdTe-PAAm-g-SA QDs in the body by binding to HSA and BSA, which could be a useful guideline for the estimation of QDs as a drug carrier.

Investigations on the interactions of DiAmsar with serum albumins: Insights from spectroscopic and molecular docking techniques.

Diamine-sarcophagine (DiAmsar) binding to human serum albumin (HSA) and bovine serum albumin (BSA) was investigated under simulative physiological conditions. Fluorescence spectra in combination with Fourier transform infrared (FT-IR), UV-visible (UV-vis) spectroscopy, cyclic voltammetry (CV), and molecular docking method were used in the present work. Experimental results revealed that DiAmsar had an ability to quench the HSA and BSA intrinsic fluorescence through a static quenching mechanism. The Stern-Volmer quenching rate constant (Ksv ) was calculated as 0.372 × 10(3) M(-1) and 0.640 × 10(3) M(-1) for HSA and BSA, respectively. Moreover, binding constants (Ka ), number of binding sites (n) at different temperatures, binding distance (r), and thermodynamic parameters (∆H°, ∆S°, and ∆G°) between DiAmsar and HSA (or BSA) were calculated. DiAmsar exhibited good binding propensity to HSA and BSA with relatively high binding constant values. The positive ∆H° and ∆S° values indicated that the hydrophobic interaction is main force in the binding of the DiAmsar to HSA (or BSA). Furthermore, molecular docking results revealed the possible binding site and the microenvironment around the bond.

Study on the interaction of Co (III) DiAmsar with serum albumins: spectroscopic and molecular docking methods.

This study was designed to examine the interaction of cobalt-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane-1,8-diamine (Co(III) DiAmsar) as a hexadentate ligand with human serum albumin (HSA) and bovine serum albumin (BSA) under physiological conditions in Tris-HCl buffer solution at pH 7.4. To this aim, at first, Co (III) DiAmsar was synthesized and characterized by nuclear magnetic resonance (NMR), and mass spectroscopy and then its interaction with HSA and BSA was investigated by means of various spectroscopic methods (Fourier transform infrared (FT-IR), UV-visible (UV-vis), fluorescence, and cyclic voltammetry (CV)) and molecular docking technique. The results of fluorescence titration revealed that the Co (III) DiAmsar strongly quench the intrinsic fluorescence of HSA and BSA through a static quenching procedure. Binding constants (Ka) and the number of binding sites (n∼1) were calculated using Stern-Volmer equations. The ΔG parameters at different temperatures were calculated. Subsequently, the values of ΔH and ΔS were also calculated, which revealed that the van der Waals and hydrogen bonding interaction splay a major role in Co (III) DiAmsar-HSA and Co (III) DiAmsar-BSA associations. The distance r between donor (HSA and BSA) and acceptor (Co (III) DiAmsar) was obtained according to fluorescence resonance energy transfer. The data obtained by the molecular modeling study revealed the surrounding residues of HSA and BSA around Co (III) DiAmsar.

Synthesis of a novel supermagnetic iron oxide nanocomposite hydrogel based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) onto salep for controlled release of drug.

In this research, a novel supermagnetic iron oxide nanocomposite hydrogel was prepared using simultaneous in situ formation of iron oxide nanoparticles (IONs) and three-dimensional cross-linked polymer networks based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) (PDMA) onto salep (PDMA-g-salep). The prepared ION-PDMA-g-salep hydrogel was systematically characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDAX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). In addition, the ION-PDMA-g-salep hydrogel exhibits favorable swelling properties that are sensitive to temperature, pH, and external magnetic field (EMF). The drug release behavior of the prepared hydrogel under EMF, different temperatures and pHs was also studied for the evaluation of the release mechanism and determination of diffusion coefficients. Finally, the antibacterial activity and cytotoxicity studies of the prepared hydrogel were examined. These results suggested that the ION-PDMA-g-salep hydrogel could be a promising candidate for biological dressing applications.

One-pot synthesis of biocompatible superparamagnetic iron oxide nanoparticles/hydrogel based on salep: characterization and drug delivery.

This work describes synthesis of biocompatible magnetic iron oxide nanoparticles/hydrogel based on salep (MION-salep hydrogel) by a facile one-pot strategy. The prepared sample was characterized by techniques like scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDAX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The obtained MION had an 8 nm diameter with a narrow size distribution and was superparamagnetic with large saturation magnetization at room temperature. The most attractive feature of the obtained sample was its swelling properties under external magnetic field (EMF), different temperatures, and pHs. Moreover, MION-salep hydrogel showed ability to deferasirox release at pH=7 with non-Fickian diffusion mechanism. An in vitro cytotoxicity study implied that the as-synthesized sample is nontoxic.

Optical properties of water soluble CdSe quantum dots modified by a novel biopolymer based on sodium alginate.

Water soluble CdSe quantum dots (QDs) were modified using a novel biopolymer based on the graft copolymerization of poly (acrylic acid) as a monomer onto sodium alginate as a backbone at room temperature. The obtained CdSe QDs were characterized by Fourier transform infrared spectrometer, thermo-gravimetry analysis, transmission electron microscopy, and dynamic light scattering. Optical properties of the prepared CdSe QDs were investigated by absorption and fluorescence spectra. It was found that the resultant QDs incredibly exhibited high fluorescence intensity and quantum yields. Lastly, the influence of the aging time on the fluorescence intensity of the modified CdSe QDs was studied by their fluorescence spectra. Due to the optical behavior of this modified QDs; it could be of potential interest in biological systems.

A novel and green biomaterial based silver nanocomposite hydrogel: synthesis, characterization and antibacterial effect.

In the present study, we report a facile and eco-friendly method for the preparation of a novel silver nanocomposite hydrogel (SNH) based on poly(acrylic acid) (PAA) grafted onto salep as a water soluble polysaccharide backbone. The presence of inorganic silver nanoparticles (nano-Ag) in the hydrogel was confirmed by thermo-gravimetric (TG) analysis. The TEM images illustrated the presence of embedded nano-Ag throughout the hydrogel matrix. In addition, the transmission electron microscopy (TEM) images showed that the formed nano-Ag had an average particle size of 5-10 nm. The potential of obtained SNH was examined for Tetracycline hydrochloride (TH) release in simulated colon conditions. Lastly, the in vitro antibacterial properties of the obtained optimum sample were successfully evaluated against gram-negative and gram-positive bacteria.

Optical properties of water-soluble CdTe quantum dots passivated by a biopolymer based on poly((2-dimethylaminoethyl) methacrylate) grafted onto κ-carrageenan.

Poly ((2-dimethylaminoethyl) methacrylate) grafted onto κ-carrageenan (κC-g-PDMA) as a biopolymer was synthesized and applied for surface modification of water-soluble CdTe quantum dots (QDs). The effects of DMA concentration, molar ratio of κC-g-PDMA/CdTe, reaction temperature and time on optical properties of CdTe QDs were investigated via fluorescent (FL) and UV- visible spectra. The results showed that the κC-g-PDMA significantly affects the optical properties of CdTe QDs. The obtained samples were characterized by Fourier transform infrared spectrum (FT-IR), thermogravimetric (TG) analysis, and transmission electron microscopy (TEM). The antibacterial activity, antifungal assays, and cytotoxicity of modified QDs were examined, and a good biocompatibility was observed.

Hydrophilic alginate based multidentate biopolymers for surface modification of CdS quantum dots.

We report that sodium alginate and its graft-copolymers with (2-dimethylaminoethyl) methacrylate may attach to the surface of colloidal CdS-thioglycerol quantum dots (QDs) via a ligand exchange process and result in water-soluble and highly stable QD supramolecules. Optical properties of modified QDs in water showed that the emission intensity of QDs was still high after surface passivation.