Max White

Polyvinyl alcohol composite nanofibres containing conjugated levofloxacin-chitosan for controlled drug release

A range of biodegradable drug-nanofibres composite mats have been reported as drug delivery systems. However, their main disadvantage is the rapid release of the drug immediately after application. This paper reports an improved system based on the incorporation of drug conjugated-chitosan into polyvinyl alcohol (PVA) nanofibers. The results showed that controlled release of levofloxacin (LVF) could be achieved by covalently binding LVF to low molecular weight chitosan (CS) via a cleavable amide bond and then blending the conjugated CS with polyvinyl alcohol (PVA) nanofibres prior to electrospinning. PVA/LVF and PVA-CS/LVF nanofibres were fabricated as controls. The conjugated CS-LVF was characterized by FTIR, DSC, TGA and 1H NMR. Scanning electron microscopy (SEM) showed that the blended CS-PVA nanofibres had a reduced fibre diameter compared to the controls. Drug release profiles showed that burst release was decreased from 90% in the control PVA/LVF electrospun mats to 27% in the PVA/conjugated CS-LVF mats after 8h in phosphate buffer at 37°C. This slower release is due to the cleavable bond between LVF and CS that slowly hydrolysed over time at neutral pH. The results indicate that conjugation of the drug to the polymer backbone is an effective way of minimizing burst release behaviour and achieving sustained release of the drug, LVF.

Sustainable dyeing technologies

This chapter explores the sustainability issues in preparing and dyeing apparel fabrics. A background summary of dyeing chemistry and fiber–dyestuff classes is followed by a review of the impact of dyeing practice and process and machinery technology on sustainability. This section focuses on coloring cotton fabrics with reactive dyes, a combination that represents the largest volume of all apparel dyeing and contributes most to environmental loads. Effluent treatment to remove color and inorganic salts is then reviewed. The chapter concludes with a presentation of the future trends and technology developments that will have an impact on sustainability.

Slow release of levofloxacin conjugated on silica nanoparticles from poly(ɛ-caprolactone) nanofibers

ABSTRACT Composite levofloxacin (LVF)/nanofibers have been fabricated through electrospinning. Slow release was achieved by covalently binding LVF to mesoporous silica nanoparticles (MSN) through a cleavable thioester bond and then blending the MSN into poly(ϵ-caprolactone) (PCL) nanofibers. Conjugated LVF–MSN was characterized by FTIR, DSC, TGA, and solid-state C13 NMR. The structure of composite nanofibers was studied by scanning electron microscopy (SEM). Drug release profiles showed that burst release was decreased from 59% in the uniform PCL/LVF electrospun mats to 20% in the PCL/conjugated LVF–MSN mats after 1 day in phosphate buffer at 37°C, and gradual release in the latter was observed over the next 13 days. This slow release is due to the cleavable bond between LVF and MSN that can be hydrolyzed over a time and results in slow release of LVF. The results indicate that confining drug-conjugated MSN into nanofibers are effective ways to slow down the burst release of the drug. GRAPHICAL ABSTRACT

Effect of Dye Solution Ionic Strength on Dyeing of Cotton with Reactive Dyes

The controlling effect for dye exhaustion (adsorption) and diffusion (absorption) in a reactive dyeing of cotton is shown to be exerted by ionic strength in the dye solution rather than concentration of inorganic salts used as electrolytes. The study showed that the conclusion applies to both exhaust dyeing for dye exhaustion and pad dyeings for dye diffusion. Further, the addition of an alkali, even though it is not used as an electrolyte, increased the extent of exhaustion (in exhaust dyeing) and diffusion (in pad dyeing) due to increase in ionic strength of the dye solution. Hence, the total ionic strength of reactive dye solution for dye exhaustion and diffusion must be taken into account in order to ensure optimum reproducibility. Means for determining the total ionic strength of exhaust or pad dye solutions for different electrolytes are given.