Size-dependent theoretical and experimental photothermal conversion efficiency of spherical gold nanoparticles

INTRODUCTION

Due to their biocompatible and plasmonic properties, gold nanoparticles (Au NPs) are good candidates to be photosensitizers in photothermal cancer therapy (PTT).

MATERIALS AND METHODS

In this paper, the dependence of the NIR-light-to-heat energy on Au NPs size was investigated. Moreover, to determine the photosensitizing properties of gold nanoparticles, PTT was conducted on two colon cell lines: SW480 and SW620 by irradiating them with two lasers having different wavelengths.

RESULTS

Transmission electron microscopy showed that the respective sizes of Au NPs were 10 nm, 12 nm and 16 nm. Moreover, local as well as global structural measurements showed that all synthesized Au NPs were crystalline and UV-Vis spectroscopy revealed that with increasing nanoparticles size the position of the surface Plasmon resonance (SPR) peaks is shifted to higher wavelengths. Decrease of cells viability was observed, when they were cultured with Au NPs and irradiated by 650 nm and 808 nm lasers. Moreover, FTIR and Raman spectra of cells, showed structural changes in DNA, phospholipids, proteins and cholesterol caused by the addition of nanoparticles and laser irradiation. The chemical changes were more pronounced in the cells cultured with Au NPs and irradiated by 650 nm lasers and these changes were dependent on the nanoparticle size. Moreover, the viability of cells investigated by the MTS assay showed, that the percentage of dead cells (∼40%) is the highest for cells cultured with 8 nm Au NPs and irradiated by the 650 nm laser. The photothermal conversion efficiency calculated from the experimental results showed a decrease of this parameter from 70% to 55% and from 61% to 48% with increasing particle size, for 650 nm and 808 nm lasers, respectively.

CONCLUSIONS

The obtained results showed that the photothermal conversion efficiency of Au NPs is size-tunable, and can be correlated with the absorption/extinction ratios calculated by the Mie theory.

From spherical to bone-shaped gold nanoparticles-Time factor in the formation of Au NPs, their optical and photothermal properties

Using the same synthesis method, which was stopped at different time intervals, gold nanoparticles (Au NPs) with different shapes, from spherical to bone-shaped, were obtained. The physical properties of the synthesized Au NPs were investigated using transmission electron microscopy (TEM) combined with selected area electron diffraction patterns (SAED) and ultraviolet-visible spectroscopy (UV-vis). The TEM images showed, that stopping the synthesis after one minute lead to the formation of small spherical Au NPs, which evolved to the cubic shape, rods and bone-shaped Au NPs after 15 min, 30 min, 2 h, respectively. SAED patterns showed, that all the obtained Au NPs were crystalline. UV-vis spectra revealed, that the light absorbance depends on the shape of the Au NPs. Moreover, the effects of the time factor in the formation of Au NPs on the effective conversion of electromagnetic energy into thermal energy, was studied. Furthermore, simulated photothermal therapy (PTT) in combination with the obtained NPs, was done for two cancer cell lines SW480 and SW620. The mortality of cells after using the differently shaped Au NPs as photosensitizers is between 18 % and 52 % and increases with the decrease of the synthesis time.

Platinum-gold nanoraspberries as effective photosensitizer in anticancer photothermal therapy

BACKGROUND

New nanophotosensitizers for photothermal cancer therapy (PTT) are still sought. In this paper we propose fancy shaped, non agglomerated core/shell PtAu NRs nanoraspberries (PtAu NRs) as potential nanophotosensitizers in PTT.

RESULTS

Light microscopy images of two colon cancer cell lines (SW480, SW620) showed, that the laser irradiation combined with PtAu NRs caused visible changes in the cell morphology. Fourier Transform InfraRed (FTIR) and Raman spectroscopies showed chemical changes in the DNA, phospholipids, lipids and protein structures caused by laser irradiation in the presence of PtAu NRs. The MTS assay showed ~ 25% mortality of cancer cells due to the addition of PtAu NRs to the cell culture, while for laser irradiation combined with nanoparticles, the mortality of cancer cells increased to 65% for the 650 nm laser and to 60% for the 808 nm laser. The calculated photothermal conversion efficiency reached 62% and 51% for the 650 nm and 808 nm lasers, respectively.

CONCLUSIONS

PtAu NRs could be applied as effective light-absorbers in the PTT anticancer therapy.

Predicting normal densities of amines using quantitative structure-property relationship (QSPR)

This paper reports on a quantitative structure-property relationship (QSPR) approach applied to predict the normal density of amines. A heuristic method was applied to a dataset of experimental densities measured for more than 140 amines extracted from the literature. Statistical processing was performed to find the best correlations. The resulting model was validated successfully based on an external test set. The QSPR analysis showed the importance of intrinsic density, obtained by dividing molecular weight by calculated molecular volume. Further improvement of the model's predictive ability was achieved by introducing descriptors quantifying the influence of intermolecular volume. It has been shown that a simple correlation equation is sufficient to predict the density of amines with satisfactory accuracy. The equation requires only three descriptors: intrinsic density, overall or summation solute hydrogen bond acidity and a sum of intrinsic state values, each of which can be easily calculated using the Simplified Molecular Input Line Entry System Specification (SMILES). The equation provided may be applied to determine the density of amines or their derivatives which are unavailable or unknown.

Associations between bone, fat tissue and metabolic control in children and adolescents with type 1 diabetes mellitus

AIMS

To investigate the relationship between bone-derived osteocalcin (OC), osteoprotegerin (OPG), Receptor Activator of Nuclear Factor NF-ĸB ligand (RANKL), and fat tissue-derived leptin and adiponectin with a clinical outcome of type 1 diabetes mellitus (T1DM) in children and adolescents.

METHODS

78 patients (43 girls and 35 boys), aged 11.5±4.3 years with T1DM and 11 age- and BMI-matched controls were included into the study. Patients were divided into 3 groups according to HbA1c level, I - below 7% [53 mmol/mol], II - 7-9% [53-75 mmol/mol] and III - above 9% [75 mmol/mol]. Blood samples for biochemical measurements were drawn at 8.00 AM, when the patients were in a fasting state. HbA1c was measured by the standardized IFCC method. OC, OPG, RANKL, leptin and adiponectin were measured by ELISA. ANOVA, and multiple regression analysis were used for statistical analysis.

RESULTS

Significant differences in leptin and osteocalcin levels between groups with different HbA1c values were observed (p=0.03, p=0.04). Multiple regression analysis adjusted for age showed that serum OC and leptin negatively correlated with HbA1c levels (r=-0.22, p=0.004 and r=-0.27, p=0.0001, respectively). In contrast, serum OPG correlated positively with HbA1c (r=0.26, p=0.02) as well as with adiponectin (r=0.26, p=0.02) and RANKL (r=0.27, p=0.02) levels. The correlation of OC with HbA1c was the strongest in group I - patients with good metabolic control of DM (r=-0.43, p=0.03). In that group, in multiple regression analysis adjusted for age and BMI leptin correlated positively with daily dose of insulin (r=0.52, r=0.009). In group II and III in multiple regression analysis adjusted for age and BMI OC correlated negatively with leptin (r=-0.37, p=0.01).

CONCLUSIONS

Our data suggest significant relationships between bone, fat tissue and glucose metabolism in pediatric patients with T1DM. The results can confirm that poor metabolic control is associated with reduced bone formation. On the other hand fat and bone tissue can influence glucose metabolism, potentiality in insulin-dependent manner. From these data leptin or OC may be potentially used as additional therapeutic agents for T1DM.