Vilius Poderys

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating.

Two-photon excited quantum dots as energy donors for photosensitizer chlorin e6

Abstract. The excitation-related problems in photodynamic therapy of cancer might be solved by combining two-photon (TP) irradiation and quantum dots (QDs) as effective energy donors for conventional photosensitizers (PS). Here, it is demonstrated for the first time that QD–chlorin e6 (Ce6) complex formed due to the hydrophobic interaction between Ce6 molecules and lipid coating of QDs can be effectively excited via TP irradiation at 1030 nm, which spectrally coincides with the biological tissue optical window. TP absorption cross-section for free QDs and Ce6 at 1030 nm was 3325 and 13 Goeppert-Mayer, respectively. Upon TP excitation of QD−Ce6 solution, the fluorescence band of bound Ce6 molecules was observed via energy transfer from excited QDs. Increasing concentration of Ce6 resulted in quenching of the photoluminescence of QDs and an increase in the fluorescence intensity of bound Ce6 molecules. These intensity changes coincided well with those observed upon single-photon excitation of QD−Ce6 solution when QDs alone are excited. The efficiency of energy transfer in QD−Ce6 complex upon TP excitation was about 80% (QD∶Ce6 1∶5). These results indicate that the effective excitation of PS with a low TP absorption cross-section is possible in such type noncovalent complexes via energy transfer from TP excited QDs.

Accumulation and biological effects of cobalt ferrite nanoparticles in human pancreatic and ovarian cancer cells

BACKGROUND AND OBJECTIVE Superparamagnetic iron oxide nanoparticles (SPIONs) emerge as a promising tool for early cancer diagnostics and targeted therapy. However, both toxicity and biological activity of SPIONs should be evaluated in detail. The aim of this study was to synthesize superparamagnetic cobalt ferrite nanoparticles (Co-SPIONs), and to investigate their uptake, toxicity and effects on cancer stem-like properties in human pancreatic cancer cell line MiaPaCa2 and human ovarian cancer cell line A2780. MATERIALS AND METHODS Co-SPIONs were produced by Massarts co-precipitation method. The cells were treated with Co-SPIONs at three different concentrations (0.095, 0.48, and 0.95μg/mL) for 24 and 48h. Cell viability and proliferation were analyzed after treatment. The stem-like properties of cells were assessed by investigating the cell clonogenicity and expression of cancer stem cell-associated markers, including CD24/ESA in A2780 cell line and CD44/ALDH1 in MiaPaCa2 cell line. Magnetically activated cell sorting was used for the separation of magnetically labeled and unlabeled cells. RESULTS Both cancer cell lines accumulated Co-SPIONs, however differences in response to nanoparticles were observed between MiaPaCa2 and A2780 cell. In particular, A2780 cells were more sensitive to exposition to Co-SPIONs than MiaPaCa2 cells, indicating that a safe concentration of nanoparticles must be estimated individually for a particular cell type. Higher doses of Co-SPIONs decreased both the clonogenicity and ESA marker expression in A2780 cells. CONCLUSIONS Co-SPIONs are not cytotoxic to cancer cells, at least when used at a concentration of up to 0.95μg/mL. Co-SPIONs have a dose-dependent effect on the clonogenic potential and ESA marker expression in A2780 cells. Magnetic detection of low concentrations of Co-SPIONS in cancer cells is a promising tool for further applications of these nanoparticles in cancer diagnosis and treatment; however, extensive research in this field is needed.

Accumulation and Toxicity of Superparamagnetic Iron Oxide Nanoparticles in Cells and Experimental Animals

The uptake and distribution of negatively charged superparamagnetic iron oxide (Fe3O4) nanoparticles (SPIONs) in mouse embryonic fibroblasts NIH3T3, and magnetic resonance imaging (MRI) signal influenced by SPIONs injected into experimental animals, were visualized and investigated. Cellular uptake and distribution of the SPIONs in NIH3T3 after staining with Prussian Blue were investigated by a bright-field microscope equipped with digital color camera. SPIONs were localized in vesicles, mostly placed near the nucleus. Toxicity of SPION nanoparticles tested with cell viability assay (XTT) was estimated. The viability of NIH3T3 cells remains approximately 95% within 3–24 h of incubation, and only a slight decrease of viability was observed after 48 h of incubation. MRI studies on Wistar rats using a clinical 1.5 T MRI scanner were showing that SPIONs give a negative contrast in the MRI. The dynamic MRI measurements of the SPION clearance from the injection site shows that SPIONs slowly disappear from injection sites and only a low concentration of nanoparticles was completely eliminated within three weeks. No functionalized SPIONs accumulate in cells by endocytic mechanism, none accumulate in the nucleus, and none are toxic at a desirable concentration. Therefore, they could be used as a dual imaging agent: as contrast agents for MRI and for traditional optical biopsy by using Prussian Blue staining.

Protein induced formation of porphyrin (TPPS4) nanostructures

The stimulating effect of two cationic proteins lysozyme and serum albumin on TPPS4 aggregation was studied in aqueous acidic solution (pH 1) by means of absorption and fluorescence spectroscopy. At low TPPS4 concentrations (≤2μM), the presence of both proteins significantly increased formation of TPPS4 J-aggregates as compared with pure TPPS4 solution. The absorption intensity of protein-induced J-aggregates was found being dependent on protein nature, TPPS4 concentration and TPPS4/protein molar ratio. J-aggregates formed in mixed TPPS -protein solutions had a broader absorption band (490 nm), except for TPPS4:BSA at a ratio 1:10, when it was even narrower and bathochromically shifted. The formation of a new absorption band at 426 nm was also observed for both Lys and BSA at certain molar ratios. The presence of a similar absorption band at 423 nm in the pure highly concentrated TPPS solutions, in which nanotube-like structures were identified on AFM images, suggests that ordered TPPS nanostructures might be also formed in contact with protein molecules.

The Polar Sulfonic Groups Influence on Structure of Self-Assembled Tetrapyrrolic Molecules

An understanding of both the interactions between the adsorbate molecules and the interactions between adsorbates and the surface is a prerequisite to eventually controlling the selfassembly process in supramolecular aggregation. Here we report the formation of supramolecular structures (J-aggregates) whose size and aggregation pattern are controlled by changing the number of polar sulfonic groups of meso-tetra (4-sulfonatophenyl) porphine. Using atomic force microscopy we show that substituted porphyrin molecules (5,10,15,20-tetrakis(4-sulfonatophenyl) porphine (TPPS4), 5,10,15-tris(4-sulfonatophenyl)-20-phenyl porphine (TPPS3), 5,15-bis(4-sulfonatophenyl)- 10,20-diphenyl porphyne (TPPS2op) - SO3 groups are opposite each other, and 5,20-bis(4- sulfonatophenyl)-10,15-diphenyl porphyne (TPPS2a) . SO3 groups are adjacent each other) form different spatial structures. Our findings suggest that placement of functional groups that are participating in direct noncovalent interactions will allow design and construction of different supramolecular structures adsorbed to surfaces.

Synthesis and functionalization of NaGdF4:Yb,Er@NaGdF4 core–shell nanoparticles for possible application as multimodal contrast agents

Upconverting nanoparticles (UCNPs) are promising, new imaging probes capable of serving as multimodal contrast agents. In this study, monodisperse and ultrasmall core and core–shell UCNPs were synthesized via a thermal decomposition method. Furthermore, it was shown that the epitaxial growth of a NaGdF4 optical inert layer covering the NaGdF4:Yb,Er core effectively minimizes surface quenching due to the spatial isolation of the core from the surroundings. The mean diameter of the synthesized core and core–shell nanoparticles was ≈8 and ≈16 nm, respectively. Hydrophobic UCNPs were converted into hydrophilic ones using a nonionic surfactant Tween 80. The successful coating of the UCNPs by Tween 80 has been confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), photoluminescence (PL) spectra and magnetic resonance (MR) T1 relaxation measurements were used to characterize the size, crystal structure, optical and magnetic properties of the core and core–shell nanoparticles. Moreover, Tween 80-coated core–shell nanoparticles presented enhanced optical and MR signal intensity, good colloidal stability, low cytotoxicity and nonspecific internalization into two different breast cancer cell lines, which indicates that these nanoparticles could be applied as an efficient, dual-modal contrast probe for in vivo bioimaging.

Formation of self-assembled quantum dot–chlorin e6 complex: influence of nanoparticles phospholipid coating

AbstractThe clinical use of phospholipid-coated quantum dots (QDs)–photosensitizer complexes as therapeutic nanoagents depends on colloidal stability of these complexes and efficiency of Förster resonance energy transfer from QDs to bound photosensitizer molecules. In this study, we demonstrate modification of CdSe/ZnS QDs with different phospholipids such as 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (PEG–DPPE); 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000 (PEG–DOPE) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and the complex formation with photosensitizer chlorin e6 (Ce6). QDs were successfully solubilized in water by coating QDs with PEG–DPPE and PEG–DOPE phospholipids. However, an attempt to solubilize QDs using PEG-free phospholipids (DOPC) was ineffective. While QDs modified with DOPC:PEG–DOPE mixtures at molar ratios of 1:1 and 2:1 showed long-term stability in aqueous solution, colloidal solution of QDs modified by DOPC:PEG–DPPE (molar ratio 2:1) was unstable. We showed that Ce6 forms a stable complex only with QDs coated with unsaturated phospholipids PEG–DOPE and DOPC:PEG–DOPE. Close localization of Ce6 molecules to the core of QDs ensures efficient energy transfer from QDs to bound Ce6 molecules that is crucial for its further application in photodynamic therapy of cancer.

Effect of substrate piezoelectricity on surface acoustic wave propagation in humidity-sensitive structures with porphyrin layers

The impact of air humidity on surface acoustic wave (SAW) propagation in different piezoelectric substrates (lithium niobate, lithium tantalate, and gallium nitride on sapphire) with nanostructured meso-tetra(4 sulfonatophenyl) porphyrin (TPPS4) overlays has been investigated. The humidity-induced increase in SAW attenuation is proportional to the electromechanical coupling constant of the substrate and is attributed to the viscoelastic loss due to interaction of water adsorbing TPPS4 material with electric field of the SAW. The humidity-induced decrease in SAW velocity does not depend on the substrate piezoelectric properties and is explained by the changes in TPPS4 layer mechanical properties due to adsorbed moisture.

Humidity sensor using leaky surface acoustic waves in YX-LiTaO 3 with nanostructured porphyrin film

We report on fast sensing of air humidity using the leaky surface acoustic wave (LSAW) propagation in YX-LiTaO3 with hematoporphyrin (Hp) nanostructured film. Effect of humidity on transmission characteristics of the Hp-LiTaO3 two-port SAW delay line was investigated using RF network analyzer. Both the amplitude and phase of transmitted signal become strongly dependent on humidity if the Hp film is located at the reflection points of the obliquely propagating bulk acoustic wave radiated by LSAW. Typically, the transmission loss increases and the phase decreases with increasing humidity. However, for certain sample configurations, we observed the phase increase with increasing humidity. The sensor exhibits very fast response on the order of 0.25 s to abrupt humidity variations. Employment of LSAWs enabled us to implement a novel sensor configuration with separated SAW excitation/detection and sensing surfaces, which is especially promising for use with liquids and aggressive media.