N,N,N-trimethylchitosan-poly (n-butylcyanoacrylate) core-shell nanoparticles as a potential oral delivery system for acyclovir.

This study investigated the feasibility of polysaccharide-coated poly(n-butyl cyanoacrylate) (PBCA) nanoparticles for oral delivery of acyclovir (ACV). PBCA nanoparticles were obtained by the emulsion polymerization method. Chitosan was chemically modified to obtain N,N,N-trimethylchitosan (TMC), which was used to coat the nanoparticles (PBCA-TMC). Nanoparticles were characterized by dynamic light scattering, zeta potential, differential scanning calorimetry (DSC), atomic force microscopy (AFM), cytotoxicity, and the effect on the transepithelial electrical resistance (TEER) of the Caco-2 cells. The size of the coated nanoparticles (296.2 nm) was significantly larger than uncoated (175.0 nm). Furthermore, PBCA nanoparticles had a negative charge (-11.7 mV), which was inverted to highly positive values (+36.5 mV) after coating. DSC analysis suggested the occurrence of the coating, which was confirmed by AFM images. The MTT assay revealed concentration-dependent cytotoxicity for the core-shell nanoparticles. Additionally, PBCA-TMC caused a significant but reversible decrease in the Caco-2 cell monolayer TEER. Entrapped ACV (PBCA-ACV-TMC), a Biopharmaceutical Classification System class III drug substance, increased approximately 3.25 times the Papp of ACV in the Caco-2 permeability assay. The nanoparticles were also able to provide in vitro ACV controlled release using media with different pH values (1.2; 6.8; 7.4). Accordingly, this new core-shell nanoparticle showed the potential to improve the oral delivery of ACV.

Evaluation of the antimicrobial activity of chitosan and its quaternized derivative on E. coli and S. aureus growth

Abstract Chitosan is largely known for its activity against a wide range of microorganisms, in which the most acceptable antimicrobial mechanism is found to include the presence of charged groups in the polymer backbone and their ionic interactions with bacteria wall constituents. This interaction suggests the occurrence of a hydrolysis of the peptidoglycans in the microorganism wall, provoking the leakage of intracellular electrolytes, leading the microorganism to death. The charges present in chitosan chains are generated by protonation of amino groups when in acid medium or they may be introduced via structural modification. This latter can be achieved by a methylation reaction resulting in a quaternized derivative with a higher polymeric charge density. Since the charges in this derivative are permanents, it is expected a most efficient antimicrobial activity. Hence, in the present study, commercial chitosan underwent quaternization processes and both (mother polymer and derivative) were evaluated, in gel form, against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), as model bacteria. The results, as acquired from turbidity measurements, differ between materials with an expressive reduction on the Gram-positive microorganism (S. aureus) growth, while E. coli (Gram-negative) strain was less sensitive to both polymers. Additionally, the antibacterial effectiveness of chitosan was strongly dependent on the concentration, what is discussed in terms of spatial polymer conformation.

Nanoparticulas de poli (n-butil-cianoacrilato) revestidas com N,N,N,-trimetilquitosana: desenvolvimento, caracterização e estudos de permeabilidade in vitro / N,NN-trimethylchitosan coated poly (n-butyl cyanoacrylate) nanoparticles: development, characterization and in vitro permeability

A via oral é considerada preferencial para a administração de fármacos, sobretudo no tratamento de doenças crônicas. Entretanto, princípios ativos administrados por essa via podem apresentar biodisponibilidade variável e/ou limitada. Diversos tipos de sistemas de liberação vêm sendo desenvolvidos com o objetivo de melhorar esse parâmetro, dentre os quais se destacam as nanopartículas de poli (alquil-cianoacrilato) (PACA). Pelo exposto, no presente trabalho foram desenvolvidas nanopartículas de poli(n-butilcianoacrilato) (PBCA) contendo aciclovir (ACV), revestidas por N,N,N-trimetilquitosana (TMQ), um promissor promotor de absorção. A TMQ foi sintetizada com elevado rendimento e grau de quaternização de aproximadamente 73%. As nanopartículas de PBCA foram obtidas com rendimento adequado e apresentaram características físico-químicas semelhantes às descritas na literatura. Após o revestimento, foi observado um aumento no diâmetro médio, bem com uma inversão nos valores de potencial zeta. Essas observações podem indicar a ocorrência do revestimento. A partir das análises de DSC, pôde-se comprovar a eficiência do revestimento das nanopartículas pelo derivado sintetizado, já que o comportamento das nanopartículas de PBCA-TMQ foi diferente daquele obtido para a mistura física entre os constituintes da formulação. Nessa mesma perspectiva, análises de FTIR foram conduzidas e a ocorrência do revestimento foi corroborada. Além disso, as análises morfológicas por Microscopia de Força Atômica (AFM) revelaram que as nanopartículas revestidas apresentam baixa tendência à agregação, o que pode ser um indicativo de estabilidade para a formulação desenvolvida. Em relação aos ensaios de citotoxicidade, foi evidenciado que as nanopartículas de PBCA não apresentaram toxicidade significativa frente às células Caco-2, ao passo que a formulação revestida mostrou um efeito tóxico dose-dependente influenciado pelo grau de quaternização. Além disso, as nanopartículas desenvolvidas foram capazes de diminuir, reversivelmente, a Resistência Elétrica Transepitelial (RET) da monocamada de células. A fim de quantificar o fármaco associado às nanopartículas, foi desenvolvido e validado método analítico por espectrofotometria derivada com detecção no UV. Tal método mostrou-se capaz de eliminar a interferência dos excipientes, permitindo a quantificação do ACV na formulação de nanopartículas com precisão e exatidão adequadas. Assim, a porcentagem de fármaco associado às nanoestruturas pode ser calculada, obtendo-se um valor satisfatório. De maneira semelhante, foi desenvolvido e validado método por CLAE para a quantificação do fármaco nos ensaios de permeação. A metodologia proposta mostrou-se adequada considerando-se as recomendações da RE 899/03. Por meio dos ensaios de permeabilidade em células Caco-2, foi constatado que a formulação desenvolvida aumentou em 3 vezes o valor de Permeabilidade aparente (Papp) do fármaco em estudo. Além disso, as nanopartículas revestidas foram capazes de propiciar a liberação controlada do ACV nos ensaios de liberação in vitro utilizando meios com diferentes valores de pH (1,2; 6,8 e 7,4)

The oral route is considered for the administration of drugs, especially in the treatment of chronic diseases. However, drugs administered by this route may have variable and/or limited bioavailability. Various types of delivery systems have been developed with the goal of improving this parameter, among which stand out the nanoparticles of poly (alkylcyanoacrylate) (PACA).Such nanomaterials have been coated to improve stability in the gastrointestinal tract, promote greater solubility or enhance permeation. Therefore, in this work were developed nanoparticles of poly (n-butilcianoacrilato) (PBCA) containing acyclovir (ACV), coated with N,N,N-trimethylchitosan (TMC), a promising absorption promoter. The TMC was synthesized with high-yield and approximately 73% of quaternization. The PBCA nanoparticles presented physico-chemical characteristics similar to those described in the literature. After the coating, it was observed an increase in the average diameter, and a inversion on the values of zeta potential. These observations may indicate the occurrence of coating. DSC analysis could proved the efficiency of the coating of nanoparticles, since the behavior of nanoparticles of PBCA-TMC was different from those obtained for the physical mixture between the constituents of the formulation. In this same perspective, FTIR analyses were conducted and the occurrence of coating was corroborated. In addition, morphological analyses by Atomic Force Microscopy (AFM) showed that nanoparticles coated presented low tendency to aggregate, which can be an indication of stability for the formulation developed. In relation to cytotoxicity assays, it was evidenced that the PBCA nanoparticles showed no significant toxicity against the Caco-2 cells, whereas the coated formulation showed a dose-dependent toxic effect influenced by the degree of quaternization. In addition, the nanoparticles developed were able to decrease, reversibly, Transepitelial Electric Resistance (TEER) of the monolayer. In order to quantify the drug associated with nanoparticles, was developed and validated analytical method by derivative spectrophotometry with UV detection. This method was able to eliminate the interference of excipients, allowing the quantification of ACV in the formulation of nanoparticles with appropriate precision and accuracy. Thus, the percentage of drug associated with nanostructures can be calculated, obtaining a satisfactory value. Similarly, has been developed and validated HPLC method for the quantification of drug permeation tests. The proposed methodology was appropriate considering the recommendations of the RE 899/03. Through the permeability assays in Caco-2 cells, it has been found that the formulation developed increased by 3 times the value os Apparent Permeability (Papp) of ACV. In addition, the nanoparticles were able to provide controlled release of ACV in vitro using media with different pH values (1.2; 6.8 and 7.4)