ABSTRACT
Entender como se originou a vida é um dos desafios propostos pela astrobiologia. Este trabalho busca compreender como argilas aniônicas do tipo hidróxidos duplos lamelares (LDH) interagem com alguns aminoácidos quando submetido a condições presentes no passado do nosso planeta. Para tanto, foi estudada a interação dos aminoácidos cisteína (cys), cistina (cyss) e ácido glutâmico (glu) com duas variações de LDHs: hidrotalcita, que consistem em um LDH de Mg e Al (LDHal), e as piroauritas, um LDH de Mg e Fe III (LDHfe). Os LDHs foram sintetizados com cada um dos três aminoácidos por coprecipitação (cop) e reconstrução (rec). Todos os compostos produzidos foram submetidos a irradiação com UV-C (254 nm), longa exposição à temperatura de 70 °C e ciclos de hidratação e dessecação a 70 °C, tentando simular condições próximas à Terra primitiva. Os resultados obtidos indicam que os aminoácidos estão presentes no espaço interlamelar dos LDHs. Sendo que os LDHfe e os LDHal_glu se mostraram mais inertes, não sofrendo variações significativas com as simulações prebióticas. Para os LDHal_cys ocorreu a formação de ligações do tipo S-S durante a síntese; a irradiação UV-C afetou de maneira distinta os LDHs cop e rec, sendo que apenas nos reconstruídos ocorreu a formação de SO4-2. A simulação de temperatura causou o rompimento das ligações S-S e a formação de ligações S-H, enquanto os ciclos de hidratação, ao que tudo indicam, acarretam a liberação da cisteína do meio interlamelar. Essas características presentes no LDHal_cys estão, em partes, também presentes para os LDHal_cyss. De maneira geral, os LDHs são eficientes na intercalação de aminoácidos e estáveis quanto à temperatura e, em alguns casos, a radiação UV-C. Desta forma os LDHs se mostram como um mineral que pode ter tido a sua importância na Terra prebiótica, sendo aptos a atuar na retenção de aminoácidos, resistência a algumas das condições presentes e com a possibilidade de liberar estas biomoléculas novamente no ambiente, tornando-as disponíveis para o aumento de complexidade química
Understanding how life originated is one of the challenges proposed by astrobiology. This work aims to understand how layered double hydroxides (LDH), a type of anionic clay, may interact with amino acids when submitted to conditions present in prebiotic Earth. It was studied the interaction between amino acids cysteine (cys), cystine (cyss) and glutamic acid (glu) with two LDHs variations: hydrotalcite, LDH of Mg and Al (LDHal), and pyroaurite, a LDH of Mg and Fe III (LDHfe). LDHs were synthesized with each of the three amino acids by coprecipitation (cop) and reconstruction (rec). All the LDHs produced were submitted to UV-C irradiation (254 nm), long exposure to the temperature of 70 °C and cycles of hydration and desiccation at 70 °C, trying to simulated the conditions presents in primordial Earth. The results indicate that amino acids are present in the interlayer region of LDHs. Since LDHfe and LDHal_glu were shown to be more inert, they did not undergo significant variations with the prebiotic simulations. For LDHal_cys the formation of S-S type bonds occurred during the synthesis; the UV-C irradiation differently affected the LDHs cop and rec, being that only in the reconstructed the formation of SO4-2 occurred. The temperature simulation induced breakage of the S-S bonds and formation of S-H bonds, whereas the hydration cycles leaded to the release of cysteine from the interlamellar space. These features present in LDHal_cys are, partially, also present for the LDHal_cyss. In general, LDHs are efficient in the intercalation of amino acids, stable in temperature and, in some cases, to UV-C radiation. In this manner, the LDHs may have been important minerals in the prebiotic Earth, being able to act in the retention of amino acids, resisting to some of the prevailing conditions and possibly releasing these biomolecules back into the environment, making them available for increasing chemical complexity
Subject(s)
Amino Acids/chemical synthesis , Exobiology , Spectrum Analysis, RamanABSTRACT
@#The aim of this study was to evaluate the potential application of layered double hydroxide(LDH)nanosheets for ocular drug delivery. Using LDH nanosheets as carriers, carboxymethyl cellulose(CMC)as a stabilizer and pirenoxine sodium(PRN)as the model drug, CMC-PRN-LDH nanosheets were prepared. PRN-LDHs nanoparticles were synthesized via co-precipitation method. X-ray diffraction, atomic force microscopy, transmission electron microscopy and laser particle sizer were employed to characterize the physicochemical properties of LDH nanosheets, CMC-LDH nanosheets and PRN-LDH nanocomposites. Stability, accumulative release in vitro and precorneal retention in vivo of both CMC-PRN-LDH nanosheets and PRN-LDHs nanoparticles were evaluated. It was found that CMC-PRN-LDH nanosheets were electrostatically stabilized by CMC absorbed on the surface of LDH nanosheets, but PRN-LDHs nanoparticles aggregated in phosphate buffered saline. 12-hr accumulative release percentage of PRN from CMC-PRN-LDH nanosheets and PRN-LDHs nanoparticles were 70. 44% and 44. 21% in vitro, respectively. Compared with the commercial PRN eye drops, there existed 4. 18-fold increase in AUC0-6 h and 1. 79-fold in mean retention time of CMC-PRN-LDH nanosheets. Negligible levels of PRN-LDHs nanoparticles might be attributed to inter-groups difference. Draize test showed that CMC-PRN-LDH nanosheets were non-irritant to the rabbit eyes after single and repeated dosing. It suggest that this novel LDH nanosheet could be a promising carrier for ocular drug delivery with prolonged residence time.
ABSTRACT
@#Ophthalmic solution of organic-inorganic layered double hydroxides hybrid nanocomposites based on layered double hydroxides(LDH)intercalated with pirenoxine sodium(PRN)and chitosan-glutathione(CG)was prepared, characterized and evaluated using rabbit precorneal retention. Mg-Al-PRN-LDH, Zn-Al-PRN-LDH and CG-PRN-LDH were synthesized by co-precipitation. The nanocomposites were characterized by laser particle sizer, powder X-ray diffraction(X-RD), fourier transform infrared spectra(FTIR)and transmission electron micrographs(TEM). The release of PRN from Mg-Al-PRN-LDH, Zn-Al-PRN-LDH, and CG-PRN-LDH nanocomposites and API in artificial tear was compared. Based on in vivo precorneal retention studies, PRN-LDH and CG-PRN-LDH nanocomposite dispersions showed significantly higher AUC(3. 72-, 7. 59-folds)and MRT(2. 18-, 2. 60-folds)than that of the commercial eye drops group. Organic-inorganic layered double hydroxides hybrid nanocomposites CG-PRN-LDH dispersions could remarkably improve precorneal retention of PRN.
ABSTRACT
OBJECTIVE: To explore the proliferation inhibition and apoptosis induction effect of dextran-magnetic layered double hydroxide-fluorouracil (DMF) drug delivery system on colon cancer cell SW480 cultivated in vitro. METHODS: MTT experiment was used to detect the cell proliferation inhibition rates of DET-MLDH-FU, MLDH-FU and MLDH supra-molecules at various concentrations. Light microscopy and Giemsa dyeing methods were applied for characterizing the shape change of the apoptotic cells. Flow cytometric analysis was employed to test the apoptosis rates of SW480 cells treated with different drugs for 24 h. DNA ladder method was used to analyze nuclei breakup of the apoptosis cells. RESULTS: The IC50 of MLDH, MLDH-FU and DMF three-level supra-molecules for SW480 cells were 44.83(25.74, 48.78), 15.16(13.78, 16.66) and 13.33 (11.03, 15.13) μg · mL-1, respectively. The proliferation of colon cancer cells SW480 was obviously restrained after being treated with 5-Fu and equivalent MLDH, MLDH-FU and DMF of different concentrations for 24, 48 and 72 h, respectively. The result revealed that the inhibition rates increased in the sequence of MLDH
ABSTRACT
Aim: To prepare diclofenac sodium-layered double hydroxide nanohybrids(DS-LDH) and investigate its properties. Methods: The diclofenac sodium anions were hybridized with LDH by co-precipitation. The synthetic nanohybrids were characterized by various methods, such as laser particle sizer, XRD, IR, and TEM. Paddle method according to the Chinese Pharmacopoeia was used to determine the dissolution. The anti-inflammation of nanohybrids and diclofenac sodium were compared by the effect on auricular tumescence induced by xylene in mice. Results: The acidic negative ion of layered double hydroxides were replaced by the diclofenac anion to form DS-LDH. Release studies showed that the nanohybrids could serve as controlled release systems for DS. Zn-Al-NO3-LDH was proved to have character of neutral pH which is more suitable for orphthalmic preparation. The DS-LDH nanohybrids could keep the effect of anti-inflammation. Conclusion: Layered double hydroxide nanohybrids can be used as sustained-release carrier of anionic drugs. A novel type of drug-inorganic nanohybrids was prepared successfully which has a potential value of clinical application.