Glucose-modified carbosilane dendrimers: Interaction with model membranes and human serum albumin.

Glycodendrimers are a novel group of dendrimers (DDMs) characterized by surface modifications with various types of glycosides. It has been shown previously that such modifications significantly decrease the cytotoxicity of DDMs. Here, we present an investigation of glucose-modified carbosilane DDMs (first-third-generation, DDM1-3Glu) interactions with two models of biological structures: lipid membranes (liposomes) and serum protein (human serum albumin, HSA). The changes in lipid membrane fluidity with increasing concentration of DDMs was monitored by spectrofluorimetry and calorimetry methods. The influence of glycodendrimers on serum protein was investigated by monitoring changes in protein fluorescence intensity (fluorescence quenching) and as protein secondary structure alterations by circular dichroism spectrometry. Generally, all generations of DDMGlu induced a decrease of membrane fluidity and interacted weakly with HSA. Interestingly, in contrast to other dendritic type polymers, the extent of the DDM interaction with both biological models was not related to DDM generation. The most significant interaction with protein was shown in the case of DDM2Glu, whereas DDM1Glu induced the highest number of changes in membrane fluidity. In conclusion, our results suggest that the flexibility of a DDM molecule, as well as its typical structure (hydrophobic interior and hydrophilic surface) along with the formation of larger aggregates of DDM2-3Glu, significantly affect the type and extent of interaction with biological structures.

Phosphonium carbosilane dendrimers - interaction with a simple biological membrane model.

The influence of three generations of five different phosphonium carbosilane dendrimers and one ammonium carbosilane dendrimer as a reference (PMe3, PBu3, P(Et2)2(CH2)3OH, PPh3, P(MeOPh)3 and NMe3, peripheral functional groups) on dimyristoylphosphatidylcholine (DMPC) or a lipid mixture dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) of liposomes was studied by fluorescence polarization measurements and differential scanning calorimetry. All types of dendrimers interacted with neutral as well as negatively charged liposomes, but the strength and observed influence were different. Concentration, type of peripheral functional group modification and dendrimer generation were the main factors influencing the interaction. Generally, weak interactions as well as destabilization of the lipid membranes at low concentrations, regardless of liposome type, were observed in the case of DmPMe3, DmNMe3, DmPBu3 and DmP(Et2)2(CH2)3OH. Dendrimers with PPh3 and P(MeOPh)3 peripheral functional groups interacted much more strongly and increased the rigidity of liposomes. Electrostatic interactions, the hydrophobicity of substituents and charge shielding on the peripheral phosphonium group are important factors in the interaction. We suggest that, among the other types of dendrimers, the dendrimer with the P(MeOPh)3 peripheral functional group is a highly promising candidate for the design of a drug delivery system due to its positive charge, efficient interaction with lipidic membranes and low cytotoxicity.

Iowa Gambling Task in patients with early-onset Parkinson's disease: strategy analysis.

The aim of our study was to analyse decision making in early-onset Parkinson's disease (PD) patients performing the Iowa Gambling Task (IGT). We compared 19 patients with early-onset PD (≤ 45 years) on dopaminergic medication (no evidence of depression, dementia, executive dysfunction according to the Tower of London test and the Stroop test, or pathological gambling) with 20 age-matched controls. A computer version of the IGT was employed. The PD patients achieved slightly lower IGT scores than the control group. A detailed analysis based on 'shift frequencies' between the individual decks showed that the patients tended to change their preferences for the decks more frequently, with a higher preference for the 'disadvantageous' deck B. Control subjects seemed to develop a more effective strategy. These differences could be caused by the poorer ability of the patients to develop any strategy at all. We observed changes in decision making during IGT performance in patients with early-onset PD, although they had no executive dysfunction as measured by established neuropsychological tests. The more detailed analysis employed in the present study could lead to a more accurate study of IGT performance and application of IGT in clinical practice.

Striatal dopamine transporter imaging correlates with depressive symptoms and tower of London task performance in Parkinson's disease.

We studied whether the (123)I-FP-CIT uptake in the striatum correlates with depressive symptoms and cognitive performance in patients with Parkinson's disease (PD). Twenty patients with PD without major depression and/or dementia (mean age 61.7 +/- 12.7 years) underwent the (123)I-FP-CIT SPECT. Depressive symptoms and cognitive performance were assessed in the ON state. The ratios of striatal to occipital binding for the entire striatum, putamina, and putamen to the caudate (put/caud) index were calculated in the basal ganglia. The association between neuropsychiatric measures and dopamine transporter (DAT) availability was calculated; multiple regression analysis was used to assess association with age and disease duration. We found significant correlations between Montgomery and Asberg Depression Rating Scale (MARDS) and Tower of London (TOL) task scores and (123)I-FP-CIT uptake in various striatal ROIs. Multiple regression analysis confirmed the significant relationship between TOL performance and put/caud ratio (P = 0.001) and to age (P = 0.001), and between MADRS and left striatal (P = 0.005) and putaminal DAT availability (P = 0.003). Our pilot study results demonstrate that imaging with (123)I-FP-CIT SPECT appears to be sensitive for detecting dopaminergic deficit associated with mild depressive symptoms and specific cognitive dysfunction in patients with PD, yet without a current depressive episode and/or dementia.