Hamida Panezai

“Graft to” Synthesis and Ibuprofen‐Loading Performance of pH‐Sensitive PMAA–Silica Hybrid Nanoparticles with Controlled Bimodal Mesopores

Bimodal mesoporous silicas (BMMs) have been proved to be a good drug-loaded carrier. However, it did not provide stimuli sensitivity or controlled release performance yet. In the present work, a smart mesoporous silica-based pH-dependent [poly(methacrylic acid)]-silica hybrid nanoparticles (P/NN-BMMs) drug delivery system was developed and evaluated with ibuprofen (IBU) as a model drug. P/NN-BMMs were prepared by coating poly(methacrylic acid) (PMAA) onto amino-modified surface of BMMs via the graft to strategy. The structure and texture of resultant hybrid nanoparticles were determined with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, thermogravimetric analysis, N2 sorption isotherms, and elemental analysis. The PMAA acts as a molecular switch to achieve controlled drug release and the amount of grafted-PMAA can remarkably affect its performance. The drug-loading rate is decreased markedly with the increasing of the amount of grafted-PMAA, meanwhile, the drug-loading kinetics on P/NN-BMMs fits Korsmeyer-Peppas model. In addition, the drug-release amount from drug-loaded P/NN-BMMs is pH dependent, showing an increasing tendency with the increase of pH value.

Influence of alternative cations distribution in AgxLi96-x-LSX on dehydration kinetics and its selective adsorption performance for N2 and O2

Adsorption characteristics of pure gases N2 and O2 on various silver exchanged low silica X-type (AgxLi96-x-LSX) zeolites were investigated. The equilibrium adsorption isotherms of N2 and O2 were measured at 273 and 298 K. Textual and structural properties of parent and resultant AgxLi96-x-LSX were characterized by XRD, BET surface area, and SEM techniques. Kinetics of their thermal dehydration were studied by exploiting thermogravimetric and differential data (TG-DTG) obtained at three heating rates (5, 10 and 15 K) using two model-free (Kissinger and Flynn-Wall-Ozawa) and one model fitting (Coats-Redfern) methods. Forty one mechanism functions were used to evaluate kinetic triplet (activation energy, frequency factor, and most probable mechanism/model) for different stages of dehydration. Results revealed that the impact of very small content of silver on the adsorption of N2 is pronounced and attributed to weak chemical bonds formed between N2 and Ag+ clusters due to strong adsorption of N2 at low pres...

Regulating dual temperature- and pH-responsibility constructed from core-shell mesoporous hybrid silica (P(NIPAM-co-AA)@BMMs) via adjusting AA incorporation onto NIPAM

Abstract The mesoporous hybrid silicas (P@BMMs) with core-shell structure were successfully synthesized via seed polymerization method using bimodal mesoporous silica materials (BMMs) as core and dual pH- and temperature-responsive poly(N-isopropylacryl-acrylamide)-co-poly(acrylic acid) (P(NIPAM-co-AA)) copolymer as shell. Meanwhile, the obtained P@BMMs were physicochemically and morphologically characterized via X-ray diffraction, N2 adsorption-desorption isotherms, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, ultraviolet visible diffused reflection spectrum, small angle X-ray scattering (SAXS), dynamic light scattering, and thermogravimetric analysis techniques. The results indicated that P(NIPAM-co-AA) was successfully coated onto the mesoporous surface of used BMMs, while the uniform mesoporous structure of obtained P@BMMs was still preserved. Using ibuprofen (IBU) as a model drug, the influence of the P(NIPAM-co-AA) shell on the release kinetics of IBU was explored, and its performances elucidated that the P@BMMs nanoparticles presented an apparent thermo/pH-responsive properties, which could be regulated via adjusting mass ratio of AA to NIPAM, and their IBU-release kinetic profiles were favorable to Korsmeyer-Peppas model. Specially, SAXS patterns were employed to evaluate the fractal evolution of P@BMMs along with releasing time, showing the decline tendency for mass fractal value from 2.89 to 2.56 during the release time of 0.25–24u2009h. Graphical Abstract

Facile synthesis and fractal feature of pH-responsive poly(acrylic acid) hollow microspheres for ibuprofen delivery

ABSTRACT The pH-responsive hollow poly(acrylic acid) (HPAA) microspheres with regulated cavity structure and various shell thicknesses were synthesized. Their structural parameters and textural properties were characterized by various techniques. The ibuprofen loading results indicate the good drug loading capabilities of HPAA microspheres from 13.81 to 17.18%. Their ibuprofen release properties demonstrated their good pH sensitivity and distance-controlled drug diffusion process. Specially, the small-angle X-ray scattering technique was used to suggest the surface roughness and structural irregularities of HPAA before and after drug loading and releasing. These findings clearly indicate the potential of HPAA microspheres to be used as promising candidates in drug delivery. GRAPHICAL ABSTRACT