Examination of the stability of hydrophobic (CdSe)ZnS quantum dots in the digestive tract of rats.

Semiconductor quantum dots show promise as alternatives to organic dyes for biological labelling because of their bright and stable photoluminescence. The typical quantum dots is CdSe because colloidal synthesis for nanocrystals of this semiconductor is well established. CdSe is usually passivated with zinc sulfide. While the cytotoxicity of bulk CdSe is well documented, questions about (CdSe)ZnS potential toxicity and behaviour in vivo remain unanswered. The distribution and stability of (CdSe)ZnS quantum dots in Wistar line rats' digestive tract were investigated. Hydrophobic quantum dots were mixed with fat or sonificated in water and administered orally. The distribution and stability of quantum dots moving through the digestive system of rats was followed by fluorescence spectroscopy. In both ways prepared quantum dots were degraded in the digestive tract of animals. Quantum dots mixed with fat were more stable and degraded more slowly than quantum dots sonificated in water. The data obtained suggest possible toxicity of (CdSe)ZnS quantum dots due to the liberation of Cd(2+).

[Nanoparticles in diagnostics and therapy: towards nanomedicine]. / Nanodariniai diagnostikai ir gydymui: nanomedicinos link.

Nanotechnology is an area of scientific research and technology development dealing with the structures and devices with length scales in the 1- to 100-nanometer range. Multifunctional nanoparticles that can target, diagnose, and treat diseases such as cancer are designed and developed. Numerous studies have shown that anticancer drugs encapsulated into nanoparticles can be delivered to target tumor cells and tissue. This would increase antitumor efficacy and reduce systemic side effects. Quantum dots are kind of nanoparticles with unique photochemical and photophysical properties. They are several orders of magnitude brighter than conventional fluorophores, and their emission spectra are very narrow and can be tuned by adjusting the size of the dots. Quantum dots are a new class of fluorescent labels with improved brightness and resistance against photobleaching. These properties could improve the sensitivity of biological detection and imaging by at least 10- to 100-fold. In this review, data of tumor targeting with conventional and long-circulating nanoparticles as well as applications of semiconductor quantum dots for in vivo imaging are discussed.

Spectroscopic study of TPPS4 nanostructures in the presence of bovine serum albumin.

The influence of bovine serum albumin (BSA) on the formation of J-aggregates of meso-tetra(4-sulfonatophenyl)porphine (TPPS4) in aqueous acid solution (pH 1.3) has been investigated by means of absorption and fluorescence spectroscopy. TPPS4 concentration was kept constant at 2 microM while BSA concentration was varied to get TPPS4 : BSA molar ratios from 1 : 0.005 to 1 : 20. In the presence of protein at all used concentrations the intensity of J-aggregates absorption band was higher than that in the pure solution. Spectral changes indicated that the dynamic equilibrium of the aggregated TPPS4 species was highly dependent on the molar ratio between TPPS4 and BSA. Small relative concentrations of BSA (TPPS4 : BSA, 1 : 0.005-1 : 0.1) had a stimulating effect on formation of J-aggregates. Several fractions of J-aggregates located in protein and aqueous moieties were detected in mixed solutions at intermediate BSA concentrations (TPPS4 : BSA, 1 : 0.5-1 : 8), when the absorbance intensity of the J-aggregates was the highest. At the highest used BSA concentrations (TPPS4 : BSA, 1 : 10-1 : 20) the spectral properties of the remaining J-aggregates were similar to those typical for pure porphyrin solution. Additionally, the split of the Soret band into two with peaks at 440 nm and 423 nm was followed by the simultaneous appearance of Q bands and reflected the formation of TPPS4-BSA complexes including both protonated and deprotonated TPPS4 forms.

Spectroscopic study of ALA-induced endogenous porphyrins in arthritic knee tissues: targeting rheumatoid arthritis PDT.

The inflamed synovium of rheumatoid arthritis exhibits many features typical for neoplastic tissue implying that the photodynamic therapy might be an efficient modality for chronic poliarthritis. The accumulation of endogenously produced porphyrins after administration of exogenous 5-aminolevulinic acid (ALA) in a rabbit model of rheumatoid arthritis was evaluated by fluorescence spectroscopy. Independent of the way, intravenously or intra-articularly, in which ALA was administered to the experimental animals, the highest fluorescence intensity of endogenously produced porphyrins was detected in the tissues of the inflamed joints. Besides, the application of ALA had a systemic sensitising effect on the whole organism of rabbits. The highest amount of endogenously produced porphyrins in the inflamed joints measured from the surface of the skin above the synovium tissues was detected 1-3 h after the administration of ALA. Fluorescence measurements performed on the tissue specimens ex vivo showed the predominant accumulation of porphyrins in the synovium of the inflamed joints. The fluorescence of porphyrins was also observed in the cartilage tissues taken from knee joints. However, the fluorescence spectra features indicated that the composition of porphyrins detected in the cartilage tissues was different than that in the synovial tissues. The selective accumulation of porphyrins in the inflamed synovial tissues stands up for the application of photodynamic therapy in the treatment of rheumatoid arthritis and implies the possibility to use optical non-invasive methods based on fluorescence detection of endogenously produced porphyrins for diagnostics of inflamed tissues.

[Fluorescence diagnostics of tumors]. / Fluorescencine naviku diagnostika.

The intrinsic autofluorescence properties of biological tissues can change depending on alterations induced by pathological processes. In this paper, autofluorescence properties of normal and tumor tissue are presented and possibilities of the application of autofluorescence as a parameter for in situ cancer detection in different organs are discussed. Data obtained during in vivo measurements of normal and pigmented skin autofluorescence are presented. Autofluorescence of experimental tumor (hepatoma A22) was measured to discriminate the optical differences between necrotic, non-necrotic and hemorrhagic areas of tumor and healthy tissue. It was concluded that the uneven distribution of endogenous porphyrins fluorescence in non-necrotic tumor tissue as well as the absence of endogenous porphyrins fluorescence in the small experimental tumors complicated the diagnosis of cancerous tissue based on the autofluorescence measurements.