Enhancing the Kinetic Stability of Polymeric Nanomicelles (PLGA) Using Nano-Montmorillonite for Effective Targeting of Cancer Tumors.

The toxic profile of chemical cross-linkers used in enhancing the stability of self-assembled nanomicelles made of amphiphilic polymeric materials hinders their use in clinical applications. This study was aimed to use the layered structure of Na-montmorillonite (MMT) as a stabilizer for nanomicelles made of poly(d,l-lactide-co-glycolide) (PLGA) amphiphilic polymer. The size of Na-MMT was reduced below 40 nm (nano-MMT) by processing in an attritor prior to its incorporation with PLGA. Hybrid PLGA nano-MMT (PM) nanoparticles (NPs) were prepared using dialysis nanoprecipitation. The size distribution was measured using dynamic light scattering (DLS). Loading 1250 µg of the model drug molecule curcumin to PM (PMC) resulted in obtaining 88 nm-sized particles, suitable for passive targeting of cancer tumors. The structure of nano-MMT and its position in PMC were investigated using FT-IR, differential scanning chalorimetry (DSC), XRF, XRD, ESEM, and EDAX assays, all of which showed the exfoliated structure of nano-MMT incorporated with both hydrophilic and hydrophobic blocks of PLGA. Curcumin was mutually loaded to PLGA and nano-MMT. This firm incorporation caused a serious extension in the release of curcumin from PMC compared to PLGA (PC). Fitting the release profile to different mathematical models showed the remarkable role of nano-MMT in surface modification of PLGA NPs. The ex vivo dynamic model showed the enhanced stability of PMC in simulated blood flow, while cytotoxicity assays showed that nano-MMT does not aggravate the good toxic profile of PLGA but improves the anticancer effect of payload. Nano-MMT could be used as an effective nontoxic stabilizer agent for self-assembled NPs.

Wetting properties of blood lipid fractions on different titanium surfaces.

BACKGROUND: Blood is the first tissue contacting the implant surface and starting the biological interactions to enhance osseointegration and stimulate bone formation with the progenitor cytokines, chemokines, and growth factors. The coagulation cascade initiates the first step of osseointegration between implant and neighboring tissues. The wound healing may be inadequate unless the blood wets the implant surface properly. Wettability is one of the most important features of the implant surface while lipid level constitutes a milestone that may change the energy of blood, which determines its distribution on implant material. Thus, the aim of this study was to evaluate the effect of lipid component of blood as cholesterol and its treatment on their wetting behavior of titanium surfaces. METHODS: Five surface groups were formed including grade 4 titanium-machined, grade 4 titanium-SLA, grade 4 titanium-SLActive, Roxolid-SLA, and Roxolid-SLActive. In healthy, hyperlipidemic, and treatment situations, blood was taken from eight rabbits and dropped to the disc surfaces. Contact angles were measured between the blood samples and disc surfaces. RESULTS: A significant difference was found between both machined and SLActive surfaces, SLA and SLActive surfaces in the hyperlipidemic period, and only Roxolid-SLA and SLActive surfaces during the treatment period. When evaluated according to time, only grade 4-machined and Grade 4-SLA surfaces showed a significant difference. CONCLUSIONS: Our findings indicated that each period has its own characteristics and showed the importance of cholesterol in blood structure on applicability of implant surfaces.

Contribution of cobalt ion precipitation to adsorption in ion exchange dominant systems.

Contribution of metal ion precipitation to the adsorption of Co2+ ions from aqueous solutions onto sepiolite has been analyzed as a function of pH. Abstraction and precipitation isotherms are constructed to isolate the precipitation of cobalt from the real adsorption. The contribution of all cobalt species against pH is calculated from the available solubility products or acid constants. It is found that at pH 8.2, which is the onset of cobalt hydroxide precipitation, the distribution of adsorbed cobalt species is as follows: 92% Co2+, 7% CoOH+ and 1% Co(OH)2. The experimental values are in accord with the calculated uptake of cobalt species onto sepiolite. Adsorption of cobalt ions onto sepiolite before precipitation of cobalt is governed by ion exchange between the released Mg2+ ions from sepiolite matrix and those adsorbed Co2+ ions; this behavior differs from typical oxide (titanium dioxide) and silicate (quartz) minerals. However, adsorption of cobalt onto the same materials including sepiolite follows the same trend after the region of cobalt precipitation despite distinct differences in their charge profiles.

Adsorption of anionic surfactants onto sepiolite.

Anionic surfactants constitute the main ingredients of detergents and a number of surfactant formulations used in a spectrum of diverse industries. The aim of this study is to examine the amenability of natural sepiolite to the adsorption of anionic surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS). Adsorption isotherms exhibit three regions with distinctly different slopes. The first region is characterized by the complexation of anionic surfactants with Mg2+ ions at the octahedral sheet or hydrogen bonding between the oxygen groups of anionic head groups of surfactant and H+ of the bound or zeolitic water. The Mg2+ ions released from sepiolite leads to the precipitation of magnesium salt of surfactant in the second region. The third region marks both the beginning of plateau region and micellar dissolution of the precipitate. The effect of temperature on surfactant adsorption for SDS/sepiolite system was utilized to calculate such thermodynamic parameters as the free energy of adsorption (DeltaG(ads)(degrees)) and the heat of adsorption (DeltaH(ads)(degrees)). The low value of DeltaH(ads)(degrees) (1.87 kJ/mol) is an evidence for the physical adsorption of anionic surfactants onto sepiolite. The relatively large value of entropic contribution (-TDeltaS(ads)(degrees)) indicates that the adsorption of anionic surfactants onto sepiolite is entropically governed.