ABSTRACT
We report the preparation of mesoporous silica nanoparticles covered by layer by layer (LbL) oppositely charged weak polyelectrolytes, comprising poly(allylamine hydrochloride) (PAH) and a sodium alginate, highly grafted by N-isopropylacrylamide/N-tert-butylacrylamide random copolymers, NaALG-g-P(NIPAM90-co-NtBAM10) (NaALG-g). Thanks to the pH dependence of the degree of ionization of the polyelectrolytes and the LCST-type thermosensitivity of the grafting chains of the NaALG-g, the as-prepared hybrid nanoparticles (hNP) exhibit pH/thermo-responsive drug delivery capabilities. The release kinetics of rhodamine B (RB, model drug) can be controlled by the number of PAH/NaALG-g bilayers and more importantly by the environmental conditions, namely, pH and temperature. As observed, the increase of pH and/or temperature accelerates the RB release under sink conditions. The same NaALG-g was used as gelator to fabricate a hNP@NaALG-g hydrogel composite. This formulation forms a viscous solution at room temperature, and it is transformed to a self-assembling hydrogel (sol-gel transition) upon heating at physiological temperature provided that its Tgel was regulated at 30.7 °C, by the NtBAM hydrophobic monomer incorporation in the side chains. It exhibits excellent injectability thanks to its combined thermo- and shear-responsiveness. The hNP@NaALG-g hydrogel composite, encapsulating hNP covered with one bilayer, exhibited pH-responsive sustainable drug delivery. The presented highly tunable drug delivery system (DDS) (hNP and/or composite hydrogel) might be useful for biomedical potential applications.
ABSTRACT
Poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) linear diblock copolymer and polystyrene-poly(ethylene oxide) (PS10PEO10) heteroarm star copolymer were used as building elements to prepare organic-inorganic hybrids. By using the layer-by-layer (LbL) methodology, these elements were integrated on mesoporous silica through non-covalent interactions, namely, ionic and H-bonding. For the latter, tannic acid (TA) was used as an intermediate layer. The deposition of the various layers was monitored by thermogravimetric analysis (TGA), electrophoretic measurements, and confocal microscopy. The final silica hybrid, bearing alternating P2VP-b-PEO and PS10PEO10 star layers was capable of carrying one hydrophilic and two hydrophobic chemical species in distinct compartments. These multicompartmental organic-inorganic hybrids could be used as nanostructured carriers for pH-responsive multiple drug delivery and potential theranostic applications.
ABSTRACT
The main aim of this article is to investigate whether there is a significant long-term association between bullying at school and drug use later in life. A meta-analysis is presented based on results from major prospective longitudinal studies with available unadjusted and adjusted effect sizes. Results are based on thorough systematic searches of the literature across 19 databases and 63 journals. The unadjusted summary effect size suggests that youth who bully are at least twice as likely compared with noninvolved students to use drugs later in life (OR = 2.22, 95% CI: 1.60-3.07). The adjusted summary effect size is markedly reduced to an OR of 1.41 (95% CI: 1.20-1.66) suggesting that a lot of variation in the final model is explained by other contributing factors, while bullying has a significant yet small effect over and above the contribution of these factors. Contributing factors include childhood risks falling within the individual, family, and school domains that are significantly associated with both the predictor and the outcome. It is concluded that school bullying, drug use, and other problem behaviors are intercorrelated; thus, highlighting the need to create a meaningful holistic framework for the prevention of drug problems and other associated mental, emotional, and behavioral maladies. Implications for policy and practice arising from these findings are discussed.
