Poly(lactide-co-glycolide)-rifampicin nanoparticles efficiently clear Mycobacterium bovis BCG infection in macrophages and remain membrane-bound in phago-lysosomes.

Nanoparticles (NPs) are increasingly used as biodegradable vehicles to selectively deliver therapeutic agents such as drugs or antigens to cells. The most widely used vehicle for this purpose is based on copolymers of lactic acid and glycolic acid (PLGA) and has been extensively used in experiments aimed at delivering antibiotics against Mycobacterium tuberculosis in animal models of tuberculosis. Here, we describe fabrication of PLGA NPs containing either a high concentration of rifampicin or detectable levels of the green fluorescent dye, coumarin-6.

Temperature-induced aggregation kinetics in aqueous solutions of a temperature-sensitive amphiphilic block copolymer.

Time effects for the temperature-induced association complexes in solutions of the thermoresponsive poly(N-isopropylacrylamide)-block-poly(ethylene glycol)-block-poly(N-isopropylacrylamide) (PNIPAAM(69)-b-PEG(23)-b-PNIPAAM(69)) copolymer that exhibit a lower critical solution temperature were studied by means of turbidimetry and dynamic light scattering (DLS). The DLS results clearly show that at temperatures below the cloud point (CP) unimers coexist with intermicellar structures, which contract as the CP is approached. At this stage, no time effect was detected.

Characterization of polyelectrolyte features in polysaccharide systems and mucin.

This review elucidates several aspects on the behavior of charged polysaccharides and mucin. Viscosification of dilute aqueous solutions of hyaluronan (HA) occurs in the course of time at low shear flow, whereas shear thinning as time evolves is found at moderate shear rates. Hydrogen bonds and electrostatic interaction play an important role for the emergence of these features.

Intramolecular and intermolecular association during chemical cross-linking of dilute solutions of different polysaccharides under the influence of shear flow.

Effects of shear flow on intramolecular and intermolecular associations of dilute aqueous alkali solutions of dextran, hydroxyethylcellulose (HEC), and a hydrophobically modified analogue (HM-HEC) in the presence of a chemical cross-linker agent were characterized with the aid of viscometry and rheo-small-angle light scattering (rheo-SALS) methods. The picture that emerges at short times in the course of cross-linking of the polymer solutions under the influence of a constant shear rate is that HEC coils contract because of intramolecular cross-linking, whereas the HM-HEC species show an incipient association and the dextran molecules are unaffected. At longer times, interchain cross-linking of the polymers promoted the growth of large flocs, which were disrupted by shear forces when they were sufficiently large.

Effect of pH on the association behavior in aqueous solutions of pig gastric mucin.

In this study, dynamic light scattering (DLS), turbidity, and rheo-small angle light scattering (rheo-SALS) methods have been utilized to examine the impact of pH (1 < or = pH < or = 7) on aqueous solutions of noncommercial purified pig gastric mucin. The asymmetric flow field-flow fractionation (AFFFF) measurements established that the mucin sample has a high molecular weight and is polydisperse. DLS measurements on dilute solutions of mucin disclosed large interchain aggregates at pH 2, where the polymer has a low charge density or is uncharged.

Characterization of the chemical degradation of hyaluronic acid during chemical gelation in the presence of different cross-linker agents.

Dynamic light scattering (DLS) and rheological experiments have been performed on semidilute aqueous hyaluronic acid (HA) solutions during the chemical cross-linking process with a water-soluble carbodiimide (WSC) to produce a hydrogel. The formation and destruction of the gel are characterized. The results suggest that the gel is cross-linked via ester linkages and at later stage in the process, the omnipresent hydrolysis of interpolymer ester linkages and glycosidic bonds prevails, leading to disruption of the gel.

Effect of hydrophobic modification on rheological and swelling features during chemical gelation of aqueous polysaccharides.

Rheological characteristics during chemical gelation with the cross-linker ethylene glycol diglycidyl ether (EGDE) of semidilute aqueous solutions of hydroxyethylcellulose (HEC) and of two hydrophobically modified analogues (HM-1-HEC and HM-2-HEC) are reported. In addition, rheological features of gelling samples (dextran and its hydrophobically modified analogue (HM-dextran)) of a different structure have been examined. Some swelling experiments on these gels in the postgel region are also reported.

Effect of shear on intramolecular and intermolecular association during cross-linking of hydroxyethylcellulose in dilute aqueous solutions.

Intramolecular and intermolecular associations of dilute aqueous alkali solutions of hydroxyethylcellulose (HEC) in the presence of a chemical cross-linker agent (divinyl sulfone, DVS) are studied with the aid of dynamic light scattering (DLS) and rheological methods. At quiescent state, DLS detected only interchain aggregation of HEC during the cross-linker reaction, and the magnitude and start of this effect depend on the cross-linker concentration. The growth of clusters has been investigated at various stages in the course of the cross-linking process by quenching the reaction mixture to a lower pH.