S. S. Lukashenko

Supramolecular Systems Based on Novel Mono- and Dicationic Pyrimidinic Amphiphiles and Oligonucleotides: A Self-Organization and Complexation Study

Novel mono- and dicationic pyrimidinic surfactants are synthesized and their aggregation behavior is studied by methods of tensiometry and nuclear magnetic resonance (NMR) self-diffusion. To estimate their potentiality as gene delivery agents, the complexation with oligonucleotides (ONus) is explored by dynamic light scattering (DLS) and zeta-potential titration methods and ethidium bromide exclusion experiments. Bola-type pyrimidinic amphiphile (BPM) demonstrates rather a weak affinity to ONus. Although it induces mixed associations with ONus, only slight charge compensation changes occur at a large excess of bola, with no recharging reached. Similarly, the ethydium bromide exclusion study reveals a slow increase in the binding capacity toward an ONu with an increment in BPM concentration. The monocationic pyrimidinic surfactant (MPM) and its gemini analogue (GPM-1) are ranked as intermediates in both their aggregative activity and complexing properties toward ONus. They both form mixed associates with ONus well below the critical micelle concentrations (cmcs) of 2 and 15 mM respectively. However, GPM-1 has a much lower isoelectric point at the molar ratio surfactant/ONu r~1 compared to r~3 for MPM. This probably indicates a larger electrostatic contribution to the ONu complexation in the case of GPM-1. The most hydrophobic pyrimidinic surfactant (GPM-2), bearing three alkyl tails, demonstrates enhanced aggregative activity and binding capacity toward ONus as compared to former pyrimidinic surfactants. Due to effective aggregative (low cmc of 0.04 mM) plus binding properties (fraction of bound ONu β=0.76 at r=2.5), GPM-2 may be ranked as a promising agent for wider biological applications.

Alkylated 1,4-diazabicyclo[2.2.2]octanes: self-association, catalytic properties, and biological activity

Aggregation of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide in the presence of diethyl 4-nitrophenyl phosphate was studied using 1H NMR spectroscopy. The quantitative characteristics of the aggregation were determined. The data obtained were used to explain the catalytic effect of micelles on the hydrolysis of the phosphate. It was found that the aggregation properties and biological activity of alkylated mono- and dicationic 1,4-diazabicyclo-[2.2.2]octanes are correlated.

Self-assembling systems based on quaternized derivatives of 1,4-diazabicyclo[2.2.2]octane in nutrient broth as antimicrobial agents and carriers for hydrophobic drugs.

Aggregation properties of mono (mono-CS) and dicationic (di-CS) surfactants, namely quaternised derivatives of 1,4-diazabicyclo[2.2.2]octane (DABCO), have been evaluated in water and in nutrient broths of different pH, i.e. in Hottinger broth (рН=7.2) and Sabouraud dextrose broth (рН=5.6). Aggregation capacity of surfactants was shown to be responsible for the solubilization properties of a complex composed of a hydrophobic probe (Sudan I) and a selected drug (quercetin), contributing to the antimicrobial activity of this surfactant system. The effect of N-methyl-d-glucamine (NmDg) additive on the antimicrobial activity of mono-CS, and its aggregation and solubilization parameters, has also been evaluated. A substantial decrease in critical micelle concentration (CMC) of cationic surfactants in nutrient broths (up to 60 times) has been reported. Twofold dilution of monocationic surfactant by NmDg slightly changed the CMC of surfactant; however, it provided a remarkable increase in solubilization capacity (∼by 4 times) and decrease in its toxicity. The data anticipate the potential use of DABCO quaternized derivatives as innovative non-toxic delivery systems for hydrophobic drugs.

Catalytic properties of micellar systems based on 4-aza-1-alkyl-1-azoniabicyclo[2.2.2]octane bromides

The catalytic effect of micellar systems based on alkylated 1,4-diazabicyclo[2.2.2]octanes on the alkaline hydrolysis of butyl chloromethyl 4-nitrophenyl phosphonate is reported. The catalytic effect is due to the reactants concentrating in the micellar phase. It increases with an increase in the hydrophobicity of the surfactant. The bicyclic surfactant manifests the higher efficiency than its cyclic and noncyclic analogues. The micellization properties of alkylated 1,4-diazabicyclo[2.2.2]octanes in aqueous solutions have been investigated by the NMR method. An increase in the hydrophobicity of the surfactant decreases the critical micelle concentration and increases the hydrodynamic radius and aggregation numbers of the micelles.

Role of surface potential in the catalytic action of micelles of cationic surfactants with a hydroxyalkyl fragment in the head group

The surface potential in aqueous micellar solutions of a series of cetyltrialkylammonium bromides containing a hydroxyalkyl fragment in the head group was determined with a spectral probe (p-nitrophenol). It was found that the catalytic effect exerted by these surfactants in solution on the base hydrolysis of carboxylic acid esters is determined by two factors. First, the charged nucleophile is concentrated at the micelle surface. Second, hydrogen bonding of the substrate with the hydroxyalkyl substituents results in its activation.

Catalytic properties of polymer-colloid complexes based on polyethyleneimines and mono- and diquaternized 1,4-diazabicyclo[2.2.2]octane derivatives in the hydrolysis of phosphorus acids esters

It is established by spectrophotometry that polyethyleneimines, mono- (MQD) and diquaternized (DQD) hexadecyl derivatives of 1,4-diazabicyclo[2.2.2]octane, and mixed polymercolloid systems based thereon catalyze the hydrolysis of p-nitrophenyl alkyl chloromethylphosphonates. The catalysis efficiency depends on the structures of substrate, 1,4-diazabicyclo-[2.2.2]octane derivatives, and polyethyleneimine, pH of the medium, and the temperature. In the case of MQD, the catalytic effect changes from 20 to 80-fold with an increase in the length of phosphonate alkyl radical from R = OEt to R = OC6H13; the DQDs exhibit lower catalytic activity compared to the MQD. The most efficient catalysis (up to 90-fold acceleration) is observed for a mixed polyethylene—dicationic surfactant system where the surfactant contains the hydroxyethyl fragment in the head group, which is due to a favorable effect of the micellar microenvironment of reagents.

Geminal alkylammonium surfactants: Aggregation properties and catalytic activity

Geminal alkylammonium surfactants containing a hexamethylene spacer show a specific behavior, namely, a catalytic effect at low concentrations of the detergent in the system. The critical micellization concentrations of these surfactants are by an order of magnitude lower than those of the related surfactants with one hydrophobic fragment. The effect exerted on the hydrolysis of carboxylic acid esters by micellar structural rearrangements induced by addition of a supporting electrolyte is determined.

Cationic gemini surfactants as new agents for plasmid DNA delivery into cells

197 Gene therapy has a great potential for treating many human diseases that are currently considered incurable. Viral vectors based on adenoviruses or rett roviruses are very effective in gene delivery. Neverthe less, in view of the problems associated with immunoo genicity and biosafety of viral vectors, there remains a need to develop nonviral vectors. As an alternative to viral vectors, cationic polymers [1–3] and liposomes [4], which bind to DNA through electrostatic interacc tions and form nanosized complexes, have been invess tigated [5, 6]. Cationic agents protect DNA from degg radation by nucleases and serve as mediators in the penetration into the cell and subsequent release from endosomes, which increases the efficiency of transfecc tion. The use of cationic surfactants as nonviral vectors was described in several papers [6, 7]. It is shown that they are effective agents that provide the compaction of DNA and recharging of the complex. Despite the obvious advantages (simplicity of synthesis and forr mulation, low concentration, availability, and high complexing ability), a significant drawback of synn thetic agents based on cationic surfactants is the low transfection efficiency. In view of this, the search for new cationic vector systems is a relevant problem. In this study, we investigated alkylammonium gemm ine surfactants (AGSs) with the formula , where m = 4–12, R = СН 3 , С 2 Н 4 ОН, R 1 = nC n Н 2n + 1 , where n = 10, 12, 14, and 16. Aqueous solutions of these compounds ensure efficient delivery of DNA into cells. Gemine surfactants (alkanedyllα,ω bis(methyldialkylammonium bromides)) were pree pared under laboratory conditions as described in [8]. The structure of the obtained compounds was conn firmed by elemental analysis as well as by IR and NMR spectroscopy data. Cell line 293T (human embryonic kidney epithee lium cells), which was used as a producer of pseudoo lentiviruses and as a model target cell line, was mainn tained by the standard procedure. We used the peGFPPN1 plasmid (Clontech, United States), which is 5100 bp in length and expresses the green fluoress cent protein, and the pCIINEO plasmiddbased vector (Promega, United States), which is 5000 bp in length and does not contain the green fluorescent protein gene. HEK293T cells were replated 40 thousand cells per well one day before transfection. To transfect HEK293T cells, 50–100 thousand cells per well of a 966well plate were used. One hour before transfection, …

Micellar and liquid-crystalline properties of bicyclic fragment-containing cationic surfactant

NMR spectroscopy is employed to study the aggregation of a cationic surfactant, 4-aza-1-cetyl-1-azoniabicyclo[2.2.2]octane bromide, in aqueous solutions. Self-diffusion coefficients are determined for micelles and monomers and the hydrodynamic radius and aggregation number are calculated for micelles. Polarization microscopy data demonstrate that the examined compound is an amphotropic substance. It is found that the lyotropic liquid-crystalline system is characterized by a wider temperature range of mesophase existence as compared to the thermotropic system.

Aggregation behavior, anticorrosion effect, and antimicrobial activity of alkylmethylmorpholinium bromides

Quaternary ammonium derivatives containing a morpholinium moiety in the head group and exhibiting micelle-forming activity have been synthesized and characterized. These compounds exhibit poly-functional properties: they efficiently inhibit hydrogen sulfide and combined (H2S and CO2) corrosion of steel, are characterized by strong bactericidal activity against sulfate-reducing bacteria, and possess pronounced bacteriostatic and fungistatic effects.