Stimuli-Sensitive Self-Assembled Tubules Based on Lysine-Derived Surfactants for Delivery of Antimicrobial Proteins.

Drug delivery vectors based on amphiphiles have important features such as versatile physicochemical properties and stimuli-responsiveness. Amino acid-based surfactants are especially promising amphiphiles due to their enhanced biocompatibility compared to conventional surfactants. They can self-organize into micelles, vesicles and complex hierarchical structures, such as fibers, twisted and coiled ribbons, and tubules. In this work, we investigated the self-assembly and drug loading properties of a family of novel anionic double-tailed lysine-derived surfactants, with variable degree of tail length mismatch, designated as mLys10 and 10Lysn, where m and n are the number of carbon atoms in the tails. These surfactants form tubular aggregates with assorted morphologies in water that undergo gelation due to dense entanglement, as evidenced by light and electron microscopy. Lysozyme (LZM), an enzyme with antimicrobial properties, was selected as model protein for loading. After the characterization of the interfacial properties and phase behavior of the amphiphiles, the LZM-loading ability of the tubules was investigated, under varying experimental conditions, to assess the efficiency of the aggregates as pH- and temperature-sensitive nanocarriers. Further, the toxicological profile of the surfactants per se and surfactant/LZM hydrogels was obtained, using human skin fibroblasts (BJ-5ta cell line). Overall, the results show that the tubule-based hydrogels exhibit very interesting properties for the transport and controlled release of molecules of therapeutic interest.

Temperature-responsive self-assembled nanostructures from lysine-based surfactants with high chain length asymmetry: from tubules and helical ribbons to micelles and vesicles.

Stimuli-sensitive self-assembled nanostructures are of great relevance for the templating of nanomaterials and the design of efficient systems for the controlled delivery of molecules. Amino acid-based surfactants often display such fascinating self-assembly due to a combination of molecular features such as critical packing parameter, chirality and H-bonding interactions. Herein, we focus on a family of newly synthesized double-chained alkylcarboxylates derived from l-lysine, and designated by 8Lysn, mLys8, with n, m = 12, 14 and 16, and 12Lys16 and 16Lys12, where the numbers represent the number of C atoms in each hydrocarbon chain. The effects of the chain length asymmetry and structural isomerism of the surfactants on their interfacial properties, thermal behavior and self-assembly in water were investigated by a comprehensive toolbox, including surface tension, DSC, imaging (light microscopy, SEM, TEM and AFM) and SAXS. All the surfactants below their Krafft temperature self-organize into tubular structures of various morphologies (flat structures, twisted and coiled ribbons and hollow tubes), forming hydrogels at low surfactant concentration. Upon the solubilization phase transition, micelles or vesicles are formed depending on the surfactant structure, and the tubule-micelle or tubule-vesicle transition is thermoreversible. A molecular-level rationalization of the observed self-assembly and phase transition features is put forth.

4,9-Diaminoacridines and 4-Aminoacridines as Dual-Stage Antiplasmodial Hits.

Multi-stage drugs have been prioritized in antimalarial drug discovery, as targeting more than one process in the Plasmodium life cycle is likely to increase efficiency, while decreasing the chances of emergence of resistance by the parasite. Herein, we disclose two novel acridine-based families of compounds that combine the structural features of primaquine and chloroquine. Compounds prepared and studied thus far retained the in vitro activity displayed by the parent drugs against the erythrocytic stages of chloroquine-sensitive and -resistant Plasmodium falciparum strains, and against the hepatic stages of Plasmodium berghei, hence acting as dual-stage antiplasmodial hits.

The effect of vitamin D and zoledronic acid in bone marrow adiposity in kidney transplant patients: A post hoc analysis.

PURPOSE: Osteoblasts and adipocytes are derived from mesenchymal stem cells. An imbalance in the differentiation of these lineages could affect the preservation of bone integrity. Several studies have suggested the importance of this imbalance in the pathogenesis of osteoporosis after kidney transplant (KT), but the role of bone marrow adiposity in this process is not well known, and if the treatment with the anti-absorptive (zoledronic acid-ZA) drugs could attenuate bone loss. Thus, our objective was compare bone marrow adiposity, osteoblasts and osteocytes before and after KT, verify an association between bone remodeling process (Turnover, Volume, and Mineralization-TMV classification), the osteocyte sclerostin expression to evaluate if there is a role of Wnt pathway, as well as the effect of ZA on these cells. METHODS: We studied 29 new living-donor KT patients. One group received ZA at the time of KT plus cholecalciferol for twelve months, and the other group received only cholecalciferol. Bone biopsies were performed at baseline and after 12 months of treatment. Histomorphometric evaluation was performed in bone and bone marrow adipocytes. Sclerostin (Scl) expression in osteocytes was evaluated by immunohistochemistry. RESULTS: Some bone marrow adiposity parameters were increased before KT. After KT, some of them remained increased and they worsened with the use of ZA. In the baseline, lower bone Volume and Turnover, were associated with increased bone marrow adiposity parameters (some of them). After KT, both groups showed the same associations. Osteocyte Scl expression after KT decreased with the use of ZA. We observed also an inverse association between bone adiposity parameters and lower osteocyte sclerostin expression 12 months after KT. CONCLUSION: In conclusion, the present study suggests that KT fails to normalize bone marrow adiposity, and it even gets worse with the use of ZA. Moreover, bone marrow adiposity is inversely associated with bone Volume and Turnover, which seems to be accentuated by the antiresorptive therapy.

Lysine-based surfactants as chemical permeation enhancers for dermal delivery of local anesthetics.

The aim of this study is to investigate the efficacy of new, biocompatible, lysine-based surfactants as chemical permeation enhancers for two different local anesthetics, tetracaine and ropivacaine hydrochloride, topically administered. Results show that this class of surfactants strongly influences permeation, especially in the case of the hydrophilic and ionized drug, ropivacaine hydrochloride, that is not easily administered through the stratum corneum. It is also seen that the selected permeation enhancers do not have significant deleterious effects on the skin structure. A cytotoxicity profile for each compound was established from cytotoxicity studies. Molecular dynamics simulation results provided a rationale for the experimental observations, introducing a mechanistic view of the action of the surfactants molecules upon lipid membranes.

Morphology, thermal behavior, and stability of self-assembled supramolecular tubules from lysine-based surfactants.

Synthetic amino acid-based surfactants possess versatile aggregation properties and are typically more biocompatible and biodegradable than surfactants with conventional headgroups. This opens the possibility of a myriad of specialty applications, namely in pharmaceutics, cosmetics, biomedicine, and nanotemplating chemistry. In this work, we have investigated the interfacial and self-assembling properties in aqueous medium of novel double-chained lysine-based surfactants, with particular focus on the behavior of the dodecyl derivative, 12Lys12. Upon cooling from dilute isotropic micellar solutions, this surfactant crystallizes into micrometer-sized tubular structures that induce gelation of the system. The tubules have been characterized in terms of morphology, assembly process, thermal behavior, and stability, by using differential scanning calorimetry, light and scanning electron microscopy, and deuterium NMR. Possible mechanisms for tubule assembly are discussed, on the basis of surfactant molecular shape, H-bonding and electrostatic interactions, and chirality effects.

In vitro cytotoxicity of a thermoresponsive gel system combining ethyl(hydroxyethyl) cellulose and lysine-based surfactants.

The cytotoxicity of three lysine-derived surfactants with a gemini-like structure was evaluated on HeLa cells. The half maximal effective concentration (EC(50)) was estimated from the dose-response curves and the values indicated an increase in toxicity with the increase in alkyl chain length. The shorter chain length surfactant (C(6)) was shown to be less cytotoxic than sodium dodecyl sulfate (SDS), and all the lysine-derived surfactants were less toxic than the cationic cetyl trimethylammonium bromide (CTAB). The presence of ethyl (hydroxyethyl) cellulose (EHEC), shown previously to form thermoresponsive gels in combination with these surfactants, was found to contribute to a lower toxicity on HeLa cells. The conjecture is that the polymer-surfactant interactions in forming mixed micelles are the key contributors to the enhanced biocompatibility of the hydrogels. The most promising results were obtained in the presence of either the most hydrophilic surfactant or in the presence of the longest chain-length surfactant. For the latter, very low concentrations are needed to induce a sol-gel transition of EHEC semi-dilute solutions.

[Genotyping Colombian Mycobacterium leprae for determining disease transmission patterns]. / Genotipificación de Mycobacterium leprae Colombiano para la Determinación de Patrones de Transmisión de la Enfermedad.

OBJECTIVE: Assessing VNTR (variable-number tandem repeat) variability of Mycobacterium leprae from Colombian patients with and without prior treatment to identify potential sources of infection and to understand the patterns of disease transmission. METHODOLOGY: This was a descriptive cross-sectional study where a convenience sample of biopsies was taken from 161 multibacillary leprosy patients; diagnosis and monitoring of the disease had been requested for these patients. DNA was extracted from M. leprae and standardised using the PCR technique for M. leprae VNTR, ge-notypes were established and different clusters grouped by unweighted pair group method with arithmetic mean (UPGMA). RESULTS: 22 different VNTR genotypes were found from 161 samples, of which 100 samples (62.1%) had a single u-VNTR genotype and the remaining genotypes were VNTR 17 (5.6%), VNTR 20 (4.3%), VNTR 18 (4.3%), VNTR 14 (4.3%) and VNTR 13 (3.7%), namely those forming groups or clusters. CONCLUSION: This study showed that clones can be detected with varying degrees of virulence / aggressiveness by cluster analysis, implying the need for more monitoring programme activities which will result in a real decline in microorganism transmission.

Physicochemical and toxicological properties of novel amino acid-based amphiphiles and their spontaneously formed catanionic vesicles.

The design of efficient liposomal systems for drug delivery is of considerable biomedical interest. In this context, vesicles prepared from cationic/anionic surfactants may offer several advantages, mainly due to their spontaneity in formation and long-term stability. There is also an impending need to produce less toxic, more biocompatible amphiphiles, while maintaining the desirable aggregation properties. In this work, we present data for acute toxicity to Daphnia magna (IC(50)), and potential ocular irritation (HC(50)) for some newly prepared ionic surfactants with dodecyl chains, derived from the amino acids tyrosine (Tyr), serine (Ser), hydroxyproline (Hyp) and lysine (Lys). The micellization behavior of the compounds, evaluated from surface tension measurements, is presented and compared to more conventional ionic amphiphiles. Two types of spontaneouly formed catanionic vesicles, composed either by a dodecyltrimethylammonium bromide (DTAB)/Lys-derivative and or Ser-/Lys-derivative mixture, have also been tested for their ecotoxicity and hemolytic potential. All the micelle-forming surfactants as well as the vesicle-containing mixtures are found to have lower ecotoxicity than the reference surfactant DTAB. Moreover, the results from hemolysis and hemoglobin denaturation tests show that the Tyr- and Lys-derivatives are moderately irritant, whereas the Hyp- and Ser- ones are just slightly irritant. Even more significantly, the vesicle-containing mixtures exhibit lower hemolytic activity than the neat surfactants, a positive result for their potential use in liposomal formulations.

Spontaneous vesicle formation in catanionic mixtures of amino acid-based surfactants: chain length symmetry effects.

The use of amino acids for the synthesis of novel surfactants with vesicle-forming properties potentially enhances the biocompatibility levels needed for a viable alternative to conventional lipid vesicles. In this work, the formation and characterization of catanionic vesicles by newly synthesized lysine- and serine-derived surfactants have been investigated by means of phase behavior mapping and PFG-NMR diffusometry and cryo-TEM methods. The lysine-derived surfactants are double-chained anionic molecules bearing a pseudogemini configuration, whereas the serine-derived amphiphile is cationic and single-chained. Vesicles form in the cationic-rich side for narrow mixing ratios of the two amphiphiles. Two pairs of systems were studied: one symmetric with equal chain lengths, 2C12/C12, and the other highly asymmetric with 2C8/C16 chains, where the serine-based surfactant has the longest chain. Different mechanisms of the vesicle-to-micelle transition were found, depending on symmetry: the 2C12/C12 system entails limited micellar growth and intermediate phase separation, whereas the 2C8/C16 system shows a continuous transition involving large wormlike micelles. The results are interpreted on the basis of currently available models for the micelle-vesicle transitions and the stabilization of catanionic vesicles (energy of curvature vs mixing entropy).

Genotipificación de Mycobacterium leprae colombiano para la determinación de patrones de transmisión de la enfermedad / Genotyping colombian Mycobacterium leprae for determining disease transmission patterns

Objetivo Evaluar la variabilidad de VNTR (variable-number tandem repeat) de Mycobacterium leprae de pacientes colombianos con y sin tratamiento previo para identificar posibles fuentes de infección y entender los patrones de transmisión de la enfermedad. Metodología Estudio transversal descriptivo, en donde mediante un muestreo electivo a conveniencia se tomaron 161 biopsias de pacientes multibacilares de lepra, que habían sido solicitadas para diagnóstico y seguimiento de la enfermedad, de las cuales se realizó extracción de ADN de M. leprae y usando la técnica de PCR para VNTRs de M. leprae estandarizada, se establecieron los genotipos y los diferentes clusters mediante el agrupamiento apareado UPGMA. Resultados En las 161 muestras totales se hallaron 22 genotipos VNTRs diferentes, de las cuales 100 muestras (62,1 por ciento) pertenecían al genotipo único VNTRU, y de los genotipos restantes, los mayoritarios, es decir los que dieron lugar a formación de grupos o clusters fueron VNTR17 (5,6 por ciento), VNTR20 (4,3 por ciento), VNTR18 (4,3 por ciento), VNTR14 (4,3 por ciento) y VNTR13 (3,7 por ciento). Conclusión En este estudio se evidencia por análisis de agrupamiento que se pueden detectar clones con diferente grado de virulencia/agresividad, lo cual implica la necesidad de incrementar varias de las actividades del programa de control que darán como resultado la verdadera disminución de la transmisión del microorganismo.

Objective Assessing VNTR (variable-number tandem repeat) variability of Mycobacterium leprae from Colombian patients with and without prior treatment to identify potential sources of infection and to understand the patterns of disease transmission. Methodology This was a descriptive cross-sectional study where a convenience sample of biopsies was taken from 161 multibacillary leprosy patients; diagnosis and monitoring of the disease had been requested for these patients. DNA was extracted from M. leprae and standardised using the PCR technique for M. leprae VNTR, ge­notypes were established and different clusters grouped by unweighted pair group method with arithmetic mean (UPGMA). Results 22 different VNTR genotypes were found from 161 samples, of which 100 samples (62.1 percent) had a single u-VNTR genotype and the remaining genotypes were VNTR 17 (5.6 percent), VNTR 20 (4.3 percent), VNTR 18 (4.3 percent), VNTR 14 (4.3 percent) and VNTR 13 (3.7 percent), namely those forming groups or clusters. Conclusion This study showed that clones can be detected with varying degrees of virulence / aggressiveness by cluster analysis, implying the need for more monitoring programme activities which will result in a real decline in microorganism transmission.