Understanding the Interaction of Polyelectrolyte Architectures with Proteins and Biosystems

Inhibition of Herpes Simplex Virus Type 1 Attachment and Infection by Sulfated Polyglycerols with Different Architectures

Inhibition of herpes simplex virus type 1 (HSV-1) binding to the host cell surface by highly sulfated architectures is among the promising strategies to prevent virus entry and infection. However, the structural flexibility of multivalent inhibitors plays a major role in effective blockage and inhibition of virus receptors. In this study, we demonstrate the inhibitory effect of a polymer scaffold on the HSV-1 infection by using highly sulfated polyglycerols with different architectures (linear, dendronized, and hyperbranched). IC₅₀ values for all synthesized sulfated polyglycerols and the natural sulfated polymer heparin were determined using plaque reduction infection assays. Interestingly, an increase in the IC₅₀ value from 0.03 to 374 nM from highly flexible linear polyglycerol sulfate (LPGS) to less flexible scaffolds, namely, dendronized polyglycerol sulfate and hyperbranched polyglycerol sulfate was observed. The most potent LPGS inhibits HSV-1 infection 295 times more efficiently than heparin, and we show that LPGS has a much reduced anticoagulant capacity when compared to heparin as evidenced by measuring the activated partial thromboplastin time. Furthermore, prevention of infection by LPGS and the commercially available drug acyclovir were compared. All tested sulfated polymers do not show any cytotoxicity at concentrations of up to 1 mg/mL in different cell lines. We conclude from our results that more flexible polyglycerol sulfates are superior to less flexible sulfated polymers with respect to inhibition of HSV-1 infection and may constitute an alternative to the current antiviral treatments of this ubiquitous pathogen.

Proteins and Polyampholytes Interacting with Polyelectrolyte Brushes and Microgels: The Charge Reversal Concept Revised

Weak polyampholytes and globular proteins among them can be efficiently absorbed from solutions by polyelectrolyte brushes or microgels even if the net charge of the polyampholyte is of the same sign as that of the brush/microgel. We use a mean-field approach for calculating the free energy of insertion of a probe polyampholyte molecule into a polyelectrolyte brush/microgel. We anticipate that the insertion of the polyampholyte into similarly charged brush/microgel may be thermodynamically favorable due to the gain in the cumulative re-ionization free energy of the pH-sensitive acidic and basic residues. Importantly, we demonstrate that the polyampholyte (protein) charge sign inversion upon transfer from the bulk of the solution to the brush/microgel does not provide sufficient conditions to assure negative re-ionization free energy balance. Thus (in the absence of other driving or stopping mechanisms), charge sign inversion does not necessarily provoke spontaneous absorption of the polyampholyte into the brush/microgel.

Dendrimers as Modulators of Brain Cells

Nanostructured hyperbranched macromolecules have been extensively studied at the chemical, physical and morphological levels. The cellular structural and functional complexity of neural cells and their cross-talk have made it rather difficult to evaluate dendrimer effects in a mixed population of glial cells and neurons. Thus, we are at a relatively early stage of bench-to-bedside translation, and this is due mainly to the lack of data valuable for clinical investigations. It is only recently that techniques have become available that allow for analyses of biological processes inside the living cells, at the nanoscale, in real time. This review summarizes the essential properties of neural cells and dendrimers, and provides a cross-section of biological, pre-clinical and early clinical studies, where dendrimers were used as nanocarriers. It also highlights some examples of biological studies employing dendritic polyglycerol sulfates and their effects on glia and neurons. It is the aim of this review to encourage young scientists to advance mechanistic and technological approaches in dendrimer research so that these extremely versatile and attractive nanostructures gain even greater recognition in translational medicine.