Martin J. Bide

The use of dendrimers to modify the dyeing behaviour of reactive dyes on cotton

Cotton fabric which had been pretreated with a dendrimer displayed markedly enhanced colour strength with reactive dyes, even when dyeing had been carried out in the absence of both electrolyte and alkali. Competitive dyeing of untreated and dendrimer pretreated cotton suggests that the dendrimers offer the potential for differential-dyeing patterning possibilities. When non-competitively dyed, dendrimer pretreatment also enhances colour strength.

Reactive dye printing with mixed thickeners on viscose

The rheology of binary mixtures of three anionic thickeners, alginate, carboxymethyl starch (CMS) and a modified polyacrylic acid has been measured. Two reactive dyes were printed from pastes based on these mixtures. The printing (amount applied, penetration, fixation) and the final print (colour yield, levelness, fabric stiffening) were assessed. Several of the mixtures showed dye-dependent behavior, and evidence suggests that the CMS undergoes interactions with one of the dyes used. In small amounts alginate and CMS seem effective as a rheology modifiers, with CMS avoiding dye-dependent rheology changes and providing high colour yields. Other parameters are dye-dependent. While the study does not include the thickeners used singly, the most advantageous mixture seems to be a modified polyacrylic acid with a small addition of CMS.

The application of heterobifunctional reactive dyes to nylon 6,6: process modifications to achieve high efficiencies

A heterobifunctional monochlorotriazine/vinyl sulphone (MCT/VS) reactive dye was applied to nylon 6,6 using various pH and temperature conditions. Optimum dye exhaustion and fixation were achieved at pH 4 and 98°C. The form in which the VS moiety was present during dyeing was examined by capillary electrophoresis. Preconversion of the dye to its VS form gave improved fixation and modified dyeing methods in which alkali additions were made at various points during the dyeing were used to achieve high dye fixation.

Antibiotic Treatment of Silk to Produce Novel Infection-Resistant Biomaterials

Dye-like applications of antibiotics to silk produce infection-resistant materials for potential use in biomedical applications. Two antibiotics, doxycycline (doxy) and cipro floxacin (cipro), are applied under a variety of conditions to silk and to silk that has previously been hydrolyzed at 40°C for 20, 40, and 60 minutes. FTIR spectroscopic analyses indicate that the drastically increased sorption of antibiotics by hydrolyzed silk is attributable to both chemical and conformational changes that occur with the hydrolysis. The high sorption of doxy by hydrolyzed silk does not necessarily yield a more infection- resistant material, as determined by a zone of inhibition test. Conversely, the same hydrolysis considerably increases both the sorption of cipro and the zone of inhibition of cipro-treated silk dyed at 65 and 85°C.

The aftertreatment of acid dyes on nylon 6,6 fibres. Part 1. 1 :2 pre-metallised acid dyes

Nylon 6,6 knitted fabric was dyed using a total of eight, commercial, 1:2 pre-metallised acid dyes and the dyed samples were aftertreated using three different commercial systems, namely a syntan, a syntan/cation process and a newly developed full backtan. When all dyeings were subjected to five consecutive ISO C061C2 wash tests, it was found that while all three aftertreatments imparted improved wash fastness, the newly developed backtanning system bestowed greatest wash fastness improvement towards repeated wash testing.

Development of infection resistant polyurethane biomaterials using textile dyeing technology

Infection is a major complication when using biomaterials such as polyurethane in the clinical setting. The purpose of this study was to develop a novel infection resistant polyurethane biomaterial using textile dyeing technology. This procedure results in incorporation of the antibiotic into the polymer, resulting in a slow, sustained release of antibiotic from the material over time, without the use of exogenous binder agents. Polycarbonate based urethanes were synthesized that contained either a non-ionic (bdPU) or anionic (cPU) chain extender within the polymer backbone and cast into films. The fluoroquinolone antibiotic ciprofloxacin (Cipro) was applied to bdPU and cPU using textile dyeing technology, with Cipro uptake determined by absorbance reduction of the “dyebath.” These dyed bdPU/cPU samples were then evaluated for prolonged Cipro release and antimicrobial activity by means of spectrophotometric and zone of inhibition assays, respectively. Cipro release and antimicrobial activity by dyed cPU segments that were aggressively washed persisted over 9 days, compared with dyed bdPU and dipped cPU control segments that lasted < 24 hours. Dyed cPU segments, which remained in a static wash solution, maintained antimicrobial activity for 11 days (length of study), whereas controls again lost antimicrobial activity within 24 hours. Thus, application of Cipro to the cPU polymer by means of dyeing technology results in a slow sustained release of antibiotic with persistent bacteriocidal properties over extended periods of time.

SYNTHESIS OF A NOVEL SMALL DIAMETER POLYURETHANE VASCULAR GRAFT WITH REACTIVE BINDING SITES

Development of a small diameter (4 mm inner diameter [ID]) prosthetic vascular graft with functional groups accessible for covalent binding of recombinant hirudin (a potent anticoagulant) should create a more hemocompatible surface. The purpose of this study was to develop a technique for generating carboxylic acid groups on the surface of precast 4 mm ID poly-(carbonate urea)-urethane vascular grafts and to evaluate the accessibility of these groups. A polycarbonate based urethane with the chain extender 2,2-bis(hydroxymethyl)propionic acid was synthesized. A precast 4 mm ID poly(carbonate urea)-urethane vascular graft (Chronoflex [CF]; CardioTech International, Woburn, MA) was then placed into a 4% carboxylated polyurethane (cPU) solution (in 1% dimethyl acetamide) and incubated for 30 minutes (cPU graft). To determine the accessibility of the carboxylic acid groups, a standard textile technique using methylene blue dye was used. Macroscopic cross-sections, which were cut and evaluated for dye penetration, showed greatest concentration of carboxylic acid groups at the luminal and capsule surfaces, with minimal penetration into the mid-portion of the graft. Analysis of dye baths for absorbance reduction resulted in the cPU grafts having 3.7-fold and 5.4-fold more accessible carboxylic acid groups compared with untreated and dimethyl acetamide dipped CF grafts. Thus, a novel small diameter vascular graft has been developed that contains reactive carboxylic acid groups accessible for protein binding.

Modification of Polyester for Medical Uses

Polyester is a widely used and useful material. Its usefulness extends into the medical field, where its strength is maintained in implanted devices and materials: it is biodurable. In both medical and non-medical use, it has properties that are less than desirable. A large volume of research has been aimed at modifying the fiber, to make it more dyeable, less soil-retentive, more comfortable, less flammable, and so on. The modifications have been achieved with a wide range of techniques of several different types. These techniques, both in principle and practice, can be used to overcome the limitations that polyester faces in medical use, principally its clotting behavior, lack of infection resistance, and incorporation into body tissue.

Cytotoxicity associated with electrospun polyvinyl alcohol

Polyvinyl alcohol (PVA) is a synthetic, water-soluble polymer, with applications in industries ranging from textiles to biomedical devices. Research on electrospinning of PVA has been targeted toward optimizing or finding novel applications in the biomedical field. However, the effects of electrospinning on PVA biocompatibility have not been thoroughly evaluated. In this study, the cytotoxicity of electrospun PVA (nPVA) which was not crosslinked after electrospinning was assessed. PVA polymers of several molecular weights were dissolved in distilled water and electrospun using the same parameters. Electrospun PVA materials with varying molecular weights were then dissolved in tissue culture medium and directly compared against solutions of nonelectrospun PVA polymer in human coronary artery smooth muscle cells and human coronary artery endothelial cells cultures. All nPVA solutions were cytotoxic at a threshold molar concentration that correlated with the molecular weight of the starting PVA polymer. In contrast, none of the nonelectrospun PVA solutions caused any cytotoxicity, regardless of their concentration in the cell culture. Evaluation of the nPVA material by differential scanning calorimetry confirmed that polymer degradation had occurred after electrospinning. To elucidate the identity of the nPVA component that caused cytotoxicity, nPVA materials were dissolved, fractionated using size exclusion columns, and the different fractions were added to HCASMC and human coronary artery endothelial cells cultures. These studies indicated that the cytotoxic component of the different nPVA solutions were present in the low-molecular-weight fraction. Additionally, the amount of PVA present in the 3-10 kg/mol fraction was approximately sixfold greater than that in the nonelectrospun samples. In conclusion, electrospinning of PVA resulted in small-molecular-weight fractions that were cytotoxic to cells. This result demonstrates that biocompatibility of electrospun biodegradable polymers should not be assumed on the basis of success of their nonelectrospun predecessors.

Use of textile dyeing technology to create an infection‐resistant functionalized polyester biomaterial

Infection is a major complication when utilizing implantable devices. The purpose of this study was to create a functionalized polyethylene terephthalate (polyester) biomaterial with sustained antimicrobial properties using textile-dyeing technology. Polyester was hydrolyzed via exposure to sodium hydroxide (NaOH) to provide two functional sites within the polymeric backbone. A modified textile dyeing technique known as thermofixation or pad-heating (pad-heat) in conjunction with autoclaving was employed to directly incorporate the fluoroquinolone antibiotic Ciprofloxacin (Cipro) into polyester fibers. Woven polyester segments were placed into various concentrations of boiling NaOH solutions to create carboxylic acid and hydroxyl groups (HYD). The segments were then sprayed (padded) with a 5 mg mL(-1) Cipro solution and dried overnight, followed by exposure to intense heat and autoclaving. Untreated HYD, Cipro-dipped, and pad-heat-treated HYD segments were then washed under stringent conditions. The antimicrobial activity of the each material was determined via zone of inhibition. Untreated HYD controls had no antimicrobial activity at any of the time periods examined. Cipro-dipped HYD segments had no antimicrobial activity after 1 h. In contrast, antimicrobial activity for autoclaved, pad-heat-treated HYD segments persisted for 80 days (length of study). Autoclave usage prior to plating affected antimicrobial activity substantially. Additionally, varying hydrolysis concentrations did not significantly affect overall Cipro release. Thus, Cipro application to HYD polyester via thermofixation resulted in controlled, sustained antibiotic release over an extended period of time. The long-term infection resistance provided by this technique may address major problems of infection from which implantable devices suffer.