Noncovalent Conjugation of OVA323 to ELP Micelles Increases Immune Response

Subunit vaccines would benefit from a safe particle-based adjuvant. Elastin-like polypeptide (ELP)-based micelles are interesting candidate adjuvants due to their well-defined size and easy modification with protein-based cargo. Coiled coils can facilitate noncovalent modifications, while potentially enhancing antigen delivery through interaction with cell membranes. ELP micelles comprise ELP diblock copolymers that self-assemble above a critical micelle temperature. In this study, an amphiphilic ELP was conjugated to peptide "K", which forms a heterodimeric coiled-coil complex with peptide "E". Self-assembled "covalent" micelles containing ELP-OVA323 (i.e., model antigen OVA323 conjugated to ELP), "coiled-coil" micelles containing ELP-K/E-OVA323 and "hybrid" micelles containing ELP-K and ELP-OVA323 were shown to be monodisperse and spherical. Dendritic cells (DCs) were exposed to all micelle compositions, and T-cell proliferation was investigated. The presence of ELP-K enhanced micelle uptake and subsequent DC maturation, resulting in enhanced CD4+ T-cell proliferation, which makes ELPs with coiled coil-associated antigens a promising vaccine platform.

A Lock‐and‐Kill Anticancer Photoactivated Chemotherapy Agent †

Photosubstitutionally active ruthenium complexes show high potential as prodrugs for the photoactivated chemotherapy (PACT) treatment of tumors. One of the problems in PACT is that the localization of the ruthenium compound is hard to trace. Here, a ruthenium PACT prodrug, [Ru(3)(biq)(STF-31)](PF₆ )₂ (where 3 = 3-(([2,2':6',2″-ter- pyridin]-4'-yloxy)propyl-4-(pyren-1-yl)butanoate) and biq = 2,2'-biquinoline), has been prepared, in which a pyrene tracker is attached via an ester bond. The proximity between the fluorophore and the ruthenium center leads to fluorescence quenching. Upon intracellular hydrolysis of the ester linkage, however, the fluorescence of the pyrene moiety is recovered, thus demonstrating prodrug cellular uptake. Further light irradiation of this molecule liberates by photosubstitution STF-31, a known cytotoxic nicotinamide phosphoribosyltransferase (NAMPT) inhibitor, as well as singlet oxygen via excitation of the free pyrene chromophore. The dark and light cytotoxicity of the prodrug, embedded in liposomes, as well as the appearance of blue emission upon uptake, were evaluated in A375 human skin melanoma cells. The cytotoxicity of the liposome-embedded prodrug was indeed increased by light irradiation. This work realizes an in vitro proof-of-concept of the lock-and-kill principle, which may ultimately be used to design strategies aimed at knowing where and when light irradiation should be realized in vivo.

Spatiotemporal Control of Doxorubicin Delivery from "Stealth-Like" Prodrug Micelles

In the treatment of cancer, targeting of anticancer drugs to the tumor microenvironment is highly desirable. Not only does this imply accurate tumor targeting but also minimal drug release en route to the tumor and maximal drug release once there. Here we describe high-loading, "stealth-like" doxorubicin micelles as a pro-drug delivery system, which upon light activation, leads to burst-like doxorbicin release. Through this approach, we show precise spatiotemporal control of doxorubicin delivery to cells in vitro.

1/f noise in graphene nanopores

Graphene nanopores are receiving great attention due to their atomically thin membranes and intrinsic electrical properties that appear greatly beneficial for biosensing and DNA sequencing. Here, we present an extensive study of the low-frequency 1/f noise in the ionic current through graphene nanopores and compare it to noise levels in silicon nitride pore currents. We find that the 1/f noise magnitude is very high for graphene nanopores: typically two orders of magnitude higher than for silicon nitride pores. This is a drawback as it significantly lowers the signal-to-noise ratio in DNA translocation experiments. We evaluate possible explanations for these exceptionally high noise levels in graphene pores. From examining the noise for pores of different diameters and at various salt concentrations, we find that in contrast to silicon nitride pores, the 1/f noise in graphene pores does not follow Hooge's relation. In addition, from studying the dependence on the buffer pH, we show that the increased noise cannot be explained by charge fluctuations of chemical groups on the pore rim. Finally, we compare single and bilayer graphene to few-layer and multi-layer graphene and boron nitride (h-BN), and we find that the noise reduces with layer thickness for both materials, which suggests that mechanical fluctuations may be the underlying cause of the high 1/f noise levels in monolayer graphene nanopore devices.

Lysine acetylation can generate highly charged enzymes with increased resistance toward irreversible inactivation

This paper reports that the acetylation of lysine epsilon-NH3(+) groups of alpha-amylase--one of the most important hydrolytic enzymes used in industry--produces highly negatively charged variants that are enzymatically active, thermostable, and more resistant than the wild-type enzyme to irreversible inactivation on exposure to denaturing conditions (e.g., 1 h at 90 degrees C in solutions containing 100-mM sodium dodecyl sulfate). Acetylation also protected the enzyme against irreversible inactivation by the neutral surfactant TRITON X-100 (polyethylene glycol p-(1,1,3,3-tetramethylbutyl)phenyl ether), but not by the cationic surfactant, dodecyltrimethylammonium bromide (DTAB). The increased resistance of acetylated alpha-amylase toward inactivation is attributed to the increased net negative charge of alpha-amylase that resulted from the acetylation of lysine ammonium groups (lysine epsilon-NH3(+) --> epsilon-NHCOCH3). Increases in the net negative charge of proteins can decrease the rate of unfolding by anionic surfactants, and can also decrease the rate of protein aggregation. The acetylation of lysine represents a simple, inexpensive method for stabilizing bacterial alpha-amylase against irreversible inactivation in the presence of the anionic and neutral surfactants that are commonly used in industrial applications.

[Bioavailability of theophylline in a new oral sustained-release preparation (author's transl)]

On the basis of biopharmaceutic-pharmacokinetic and galenic aspects a new sustained-release preparation of theophylline according to the "divided-dose" principle was developed. The technological procedure used allows a reproducible manufacture of a stable product with narrow limits of pharmaceutical quality. The bioavailability of the sustained-release pellets in a dose corresponding to 350 mg active principle is examined in comparison to an aqueous solution or retard-tablet formulation on the marked (containing 260 mg drug/dose), respectively, after single or multiple dose administration to 7 healthy volunteers. The relative bioavailability of the new formulation is about 100%. During chronic application the controlled drug delivery from the sustained-release pellets warrants only slight fluctuations of plasma levels by avoiding peak concentrations. Formulations with a dosage of 200, 350 or 500 mg, respectively, allow adaptation of continuous plasma levels in the therapeutic range between 5--20 micrograms/ml according to the therapeutic necessities of a patient.

[Optimating the availability of homologous quaternary ammonium compounds/3rd communication: The influence of salts on in vitro distribution of benzilic acid esters of homologous dimethyl-(2-hydroxyethyl)-alkyl-ammoniumbromides (author's transl)]

The addition of NaBr, Na-butansulfonate or Na-trichloracetat increases the partition coefficients of homologous quaternary cholinesters of benzilic acid between n-octanol and water. In a three-phase model (water/n-octanol/water) thus the rates of equilibration increase considerably for hydrophilic compounds.

[The optimization of the availability of homologous quaternary ammonium compounds. 2. In vitro studies on the partition of homologous benzilic acid esters of dimethyl-(2-hydroxyethyl)-alkylammonium bromides]

The partition of homologous quaternary esters of benzilic acid is studied in a modified three-phase model according to Schulmann (water-n-octanol-water). The logarithms of the partition coefficients of the compounds increase linearly with increasing alkyl chain. The rate determining step for the interphase transport of hydrophilic compound is the diffusion through the organic diffusion layer. The rate constants for the transfer from the aqueous to the organic phase increase linearly with the corresponding partition coefficient, whereas the rate constants for the reverse reaction are not influenced. With increasing chain length the diffusion through the aqueous diffusion layer becomes rate determining for the interphase transport. Thus the rate constants for the transfer from the aqueous to the organic phase are independent of partition coefficients. The rate constants for the reverse transfer are inversely proportional to the corresponding partition coefficients. The half-lives of the transfer of the homologous compounds under sink conditions show a minimum between the heptyl and octyl derivative. The equilibration time decreases with increasing agitation, concentration and temperature. The significance of the results for biological problems is discussed.