Kamil Záruba

Application of gold nanoparticles in separation sciences

The review article is devoted mainly to the description of applications of gold nanoparticles (GNPs) in separation sciences, especially in electromigration and chromatographic techniques. The applications of GNPs in particular separation methods, CE, microchip CE, MEKC, CEC, HPLC and GC, are classified according to the molecular size of the analytes from low-molecular-mass compounds via medium sized substances to biopolymers (proteins and nucleic acids). A very recent and promising utilization of GNPs for sample preparation, preconcentration and preseparation of selected analytes from complex matrices is presented as well. Moreover, in two introductory sections, typical preparation procedures of the GNPs and their modifications are presented and physico-chemical and analytical methods employed for characterization of the native and modified GNPs are briefly introduced.

Synthesis of silica particles and their application as supports for alcohol dehydrogenases and cofactor immobilizations: conformational changes that lead to switch in enzyme stereoselectivity.

FTIR, circular dichroism (CD) and fluorescence spectroscopies were used to characterize conformational changes in horse liver alcohol dehydrogenase (HLADH) and ketoreductase (KRED 117) upon physical and covalent immobilizations on silica particles (functionalized with amino, epoxy and thiol groups) of different sizes. Conformational changes for immobilized enzymes were associated with high and low frequency shifts of the amide I and II bands. CD spectra of native HLADH and KRED 117 characterized with a negative peak at 222nm indicating a α-helical structure. The disappearance of the negative peak in the CD spectra of immobilized enzymes and appearance of a positive peak at 222nm supported these observations. These findings demonstrated unfolding of folded enzymes and exposure of the amino acid residues during denaturation with a red shift in tryptophan fluorescence. The decrease in specific activities (by 60-70% in all cases) for both immobilized enzymes was correlated to those of conformational changes. Silica-attached enzyme-NADH systems were evaluated for enantioselective reduction of 1-(p-methoxyphenyl)-propan-2-one. Conformational changes enhanced the enantioselectivity of immobilized HLADH with a switch in its stereoselectivity. In the case of immobilized KRED 117, kinetic values (V(max) and K(m)) were lower than that of the free enzyme, without enhancing enzyme enantio- and stereoselectivity.

Rational design of chemical ligands for selective mitochondrial targeting.

The rational design of molecules with selective intracellular targeting is a great challenge for contemporary chemistry and life sciences. Here, we demonstrate a rational approach to development of compartment-specific fluorescent dyes from the γ-aryl substituted pentamethine family. These novel dyes exhibit an extraordinary affinity and selectivity for cardiolipin in inner mitochondrial membrane and possess excellent photostability, fluorescent properties, and low phototoxicity. Selective imaging of live and fixed mitochondria was achieved in various cell lines using nanomolar concentrations of these dyes. Their high localization specificity and low toxicity enables study of morphological changes, structural complexity, and dynamics of mitochondria playing a pivotal role in many pathological diseases. These far-red emitting dyes could also serve in a variety of biomedical applications.

Oxoanion binding: a change of selectivity for porphyrin–alkaloid conjugates as a result of substitution pattern

The selective interaction of two porphyrin–brucine quaternary salts with oxoanions in a methanol/aqueous environment is described. The influence of both meta and para substitution of the tetraphenylporphyrin core with four brucine units on anion binding selectivity is discussed. The interaction of cationic porphyrin–brucine conjugates with anions are based not only on an anion-exchange mechanism; differences between the porphyrins tested also revealed the influence of peripheral substitution on the final selectivity.

Optical sensing system for ATP using porphyrin–alkaloid conjugates

Tetrabrucin-porphyrin as a sensor for ATP was designed and tested; selectivity for ATP was proved in the presence of ADP and AMP.

Quaternized brucine as a novel chiral selector

Abstract A novel recognition scaffold for interfacial enantiomer recognition was synthesized via initial N -alkylation of brucine with 6-bromohexanoic acid followed by covalent attachment of the product to 3-aminopropyl silica; chromatographic tests demonstrated the participation of an anion-exchange interaction in the chiral recognition of 2,2′-dihydroxy-1,1′-binaphthyl-3-carboxylic acid derivatives with the resulting chiral stationary phase.

Preparation of Silica Nanoparticles Loaded with Nootropics and Their In Vivo Permeation through Blood-Brain Barrier

The blood-brain barrier prevents the passage of many drugs that target the central nervous system. This paper presents the preparation and characterization of silica-based nanocarriers loaded with piracetam, pentoxifylline, and pyridoxine (drugs from the class of nootropics), which are designed to enhance the permeation of the drugs from the circulatory system through the blood-brain barrier. Their permeation was compared with non-nanoparticle drug substances (bulk materials) by means of an in vivo model of rat brain perfusion. The size and morphology of the nanoparticles were characterized by transmission electron microscopy. The content of the drug substances in silica-based nanocarriers was analysed by elemental analysis and UV spectrometry. Microscopic analysis of visualized silica nanocarriers in the perfused brain tissue was performed. The concentration of the drug substances in the tissue was determined by means of UHPLC-DAD/HRMS LTQ Orbitrap XL. It was found that the drug substances in silica-based nanocarriers permeated through the blood brain barrier to the brain tissue, whereas bulk materials were not detected in the brain.

Study of Molecular Recognition of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin-β-cyclodextrin Conjugate Covalently Immobilized on a Silica Surface

Interactions of a new porphyrin–β-cyclodextrin conjugate (1) with a number of aromatic compounds have been studied after covalent immobilization of 1 onto a solid matrix of 3-aminopropylated silica particles. The effects of both porphyrin and β-cyclodextrin moieties on interactions with achiral aromatic compounds were studied and the influence of the achiral porphyrin spacer on chiral recognition of binaphthyl derivatives by the β-cyclodextrin moiety of 1 is discussed.

Interaction of porphyrin and sapphyrin macrocycles with nucleobases and nucleosides Spectroscopic, quantum chemical and chromatographic investigation

Novel oligopyrrole macrocycle-based sorbents were prepared via amide covalent bonding of carboxylic acids of porphyrin and sapphyrin derivatives to 3-aminopropyl silica. Covalent attachment of Cu(II)-tetraphenylporphyrin formyl-derivative was performed by amine linkage. Prepared sorbents were characterized by Raman spectroscopy and elemental analysis. Retention behavior of nucleobases and nucleosides was investigated by HPLC. UV–VIS and 1 H NMR titrations were used to study the role of oligopyrrol macrocyclic receptors for selective recognition of adenine, cytosine, thymine and uracil and their nucleoside forms. The spectroscopic results were compared with quantum chemical calculations at semiempirical level and with the data obtained by HPLC measurements. Obtained data suggest that an aromatic – stacking interactions govern the HPLC separation. A different behavior was found for purine and pyrimidine bases. An introduction of Cu(II) into porphyrin macrocycle led to a dramatic increase of separation efficiency, probably due to an increase of interaction energy.

Study of receptor mediated selective anion transmembrane transport using parallel artificial membrane permeability assay

The separation performance of inorganic anions ReO4(-), Br(-), SO4(2-), and NO3(-) using porphyrin-alkaloid quaternary salt transporters is examined using parallel artificial membrane permeability assay. Active and selective transport of perrhenate is achieved by porphyrin-brucine conjugates. Herein, chlorides are used as antiporters and complete removal of perrhenates from a source solution is stimulated due to electrostatic effects.