Bojana Voncina

Durable press finishing of cotton with polycarboxylic acids. II. Ester crosslinking of cotton with dithiosuccinic acid derivative of S-triazine

The preparation of an alternative polycarboxylic acid to replace the most promising but expensive crosslinking reagent butanetetracarboxylic acid (BTCA) was reported in Part I.1 Part II studies the efficiency of the crosslinking of cotton with the dithiosuccinic acid derivative of s-triazine (HDTST). Diffuse Reflectance infrared (DR FTIR) spectroscopy in combination with wrinkle recovery angle measurements (WRA) were used to analyse the efficiency of cotton cellulose crosslinking. Energy Dispersive X-ray analysis (EDX) of the polycarboxylic acid-finished cotton fabric was performed to study sulphur distribution.

Durable press finishing of cotton with polycarboxylic acids. I. Preparation of thiosuccinyl‐s‐triazine

The preparation of an alternative polycarboxylic acid to replace the most promising, but expensive, crosslinking reagent 1,2,3,4-butanetetracarboxylic acid (BTCA) is reported. The reaction of mercaptosuccinic acid with 2,4,6-trichloro-s-triazine (cyanuric chloride) gave a dithiosuccinyl derivative. The preparation reaction was followed using horizontal ATR infrared spectroscopy and capillary electrophoresis. The final product was characterized by FTIR, capillary electrophoresis, and 1H-NMR.

Cyclodextrins in Textile Finishing

Cyclodextrins can act as hosts and form inclusion compounds with various small molecules. Such complexes can be formed in solutions, in a solid state as well as when cyclodextrins are linked to various surfaces where they can act as permanent or temporary hosts for small molecules that provide certain desirable attributes. This characteristic makes cyclodextrin a promising reagent in textile finishing.

The antimicrobial reagent role on the degradation of model cellulose film.

The effect of the antimicrobial agent TMPAC (3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride) on the cellulase activity on model cellulose substrate was investigated by in situ-null ellipsometry. The cellulases used were extracted from Trichoderma viride and Aspergillus niger, and the model cellulose film was prepared by spin-coating silicon oxide wafers with cellulose solubilized in N-methylmorpholine-N-oxide/dimethyl sulfoxide solution. Upon enzyme addition to the previously equilibrated cellulose film, the initial enzyme adsorption on the substrate was followed by an overall decrease in film mass owing to enzymatic digestion of the cellulose. The loss of cellulose film mass was associated with a non-monotonously behavior of the cellulose film thickness. The activities of the two enzymes were different, a much higher degradation rate being observed for the Trichoderma viride cellulase. The degradation rate with this cellulase decreased significantly when the cellulose film was treated with the antimicrobial agent. The antimicrobial agent did not affect the cellulose degradation catalyzed by the Aspergillus niger cellulase. It was, hence, demonstrated for the first time that, depending on the cellulase type, the antimicrobial agent can inhibit enzymatic activity at the solid-liquid interface.

Organic nanoparticulate photochromes

Photochromic organic dyes can be widely used in materials for optically rewritable data storage, photonic switches, memories, sensors, or actuators. In recent years photochromic materials based on nanoparticles became particularly focused, since they can be dispersed in colloidal aqueous suspensions or incorporated in thin films, avoiding problems of light scattering or shallow light penetration in bulk materials. Spiropyrans, spirooxazines and diarylethenes were by far the most researched photochromes in nanoparticulate systems. Great effort was made to investigate photochromic dyes incorporated into organic nanoparticles via self-assembly strategies, covalent linkage or dispersion of the molecular species in polymers (doping). Nanoparticles composed of solely photochromic dyes were prepared by laser ablation and reprecipitation techniques. Photochromic dyes were microencapsulated by self-assembly, soap free-, emulsion/microemulsion/miniemulsion or free radical- (co)polymerization. Sol-gel processing from silane precursors to poly(organo)siloxane matrix is a common method to synthesize doped or core-shell photochromic organogels. Coloured forms of some photochromes display fluorescence; however, a more effective strategy for fluorescence modulation with photochromic molecules is integrating them, covalently or noncovalently, with a separate fluorophore in the same nanoparticles. These photoresponsive nanoparticles may find applications particularly in biological fields such as cell labelling and bioimaging. The purpose of this review is to summarize the preparation methods of organic nanoparticles containing photochromic dyes and to investigate their typical properties derived from their nanoparticulate character.

Deposition and release of chlorhexidine from non-ionic and anionic polymer matrices

Therapeutic activity of locally applied drugs depends on both the thermodynamic activity of the active molecule and the pharmaceutical system which enables the release of the molecule; also the vasoconstrictive activity of vessels plays an important role. In this study, the release of chlorhexidine was assessed considering the use of ionic and non-ionic polymeric carriers at temperatures in the range between 22°C and 42°C, including the temperature of 32°C as the reference surface body temperature. The obtained release rates and concentrations of chlorhexidine, loaded to methylcellulose and poly(acrylic acid) gels, were compared with respective viscositiy, pH, and conductivity of the assessed systems. The deposition patterns of chlorhexidine in the polymeric matrix were studied using energy dispersive X-ray spectrometry to evaluate the possible influence of chlorhexidine distribution in/on the carrier on the respective release rates. This study is significant for patients with various skin temperature conditions, who are required to receive local biocides applied on skin or into the oral cavity. The obtained precipitate of polyacrylic acid-chlorhexidine preparation was extensively studied to evaluate the chlorhexidine release and to develop an application in skin and dental care.

The Study of Release of Chlorhexidine from Preparations with Modified Thermosensitive Poly-N-isopropylacrylamide Microspheres

The aim of this study was to investigate and compare the release rates of chlorhexidine (CX) base entrapped in the polymeric beads of modified poly-N-isopropylacrylamides (pNIPAMs) at temperatures below and over the volume phase transition temperature (VPTT) of synthesized polymers: pNIPAM-A with terminal anionic groups resulting from potassium persulfate initiator, pNIPAM-B with cationic amidine terminal groups, and pNIPAM-C comprising anionic terminals, but with increased hydrophobicity maintained by the N-tert-butyl functional groups. The preparations, assessed in vitro below the VPTT, release an initial burst of CX at different time periods between 120 and 240 min, followed by a period of 24 h, when the rate of release remains approximately constant, approaching the zero-order kinetics; the release rates for the polymers beads are as follows: pNIPAM-C>pNIPAM-B>pNIPAM-A. The pattern of release rates at temperature over the VPTT is as follows: pNIPAM-C>pNIPAM-A>pNIPAM-B. In the presence of pNIPAM-C, the duration between the start of the release and the attained minimal inhibitory concentration (MIC) for most of the microbes, in conditions over the VPTT, increased from 60 to 90 min. The release prolongation could be ascribed to some interactions between the practically insoluble CX particle and the hydrophobic functional groups of the polymer.

Morphological characteristics of modified freeze-dried poly(N-isopropylacrylamide) microspheres studied by optical microscopy, SEM, and DLS

Influence of the initiator and additional hydrophobic copolymer on the morphology of thermosensitive poly(N-isopropylacrylamide) (pNIPAM) microspheres, and their presumed application for the stabilization of biologically active molecules were evaluated in this study. Three different types of pNIPAM were synthesized, applying various components: PN1 is a polymer with terminal anionic groups resulting from potassium persulfate initiator; PN2 was synthesized with a 2,2′-azobis(2-methylpropionamidine) dihydrochloride initiator introducing cationic amidine terminal groups; in the PN3 polymer, anionic terminals were implemented, however, increased hydrophobicity was maintained using N-tert-butyl functional groups. Turbidity measurements of the obtained dispersions confirmed specific thermosensitivity of synthesized microspheres in the range of 32–33°C. The polymerization course was proved by infrared spectroscopy and 1H NMR assessments, whereas the size of the synthesized microspheres, expressed as planar area, was evaluated by dynamic light scattering (DLS), scanning electron microscopy (SEM) and optical microscopy (OM). The respective surface patterns of the freeze-dried microspheres were evaluated by SEM. Planar area of the synthesized macromolecules was in the range between 0.41–3.22 μm, depending on the substrates composition and the method applied for the measurements. The assessments performed in the dry stage gave higher values of the diameter and planar area of the observed microspheres. The measured diameter and planar area increased in the following order for the PN3 microspheres: DLS, OM, SEM. In the case of PN1 and PN2, the observed diameters were positioned as: DLS, SEM, OM. These differences were assigned both to varied intramolecular hydrophobic-hydrophilic interactions of the polymer chains and to the environment, i.e. low pressure in the SEM conditions and aqueous solvent in the DLS measurements. The observed gaps in the freeze-dried PN2 polymer resulted in an attempt to evaluate the application of this polymer for mechanical stabilization of certain macromolecules or nanocrystals in the size range between 10 nm and 20 nm.

Lidocaine hydrochloride preparations with ionic and non-ionic polymers assessed at standard and increased skin surface temperatures

In this study, the release of lidocaine hydrochloride was assessed considering the use of both the ionic and the non-ionic polymeric carrier at temperatures of 22°C, 32°C, and 42°C; temperature of 32°C was chosen as the reference surface body temperature. The obtained release rates and respective amounts of lidocaine hydrochloride loaded both to methylcellulose beads and polyacrylic acid beads were compared with respective viscosity, pH and conductivity of the studied systems. The release of lidocaine hydrochloride from the methylcellulose system is influenced by temperature; with the increase of temperature the release rate decreases whereas the viscosity increases. In the polyacrylic acid system, release rates are lower, however, in the first stage they are slightly increasing with the increase of temperature. The final amount of released drug after 24 h increases with the temperature of the release process environment, and it is higher in case of a methylcellulose system. The maximum differences between the released amounts for methylcellulose were in the range of 15 %, whereas in case of polyacrylic acid, the difference was approximately 12 %. Thus, this research is important for patients with differentiated skin surface temperature conditions to whom a local analgesic is to be applied.

Preparation of SMART wound dressings based on colloidal microgels and textile fibres

Wound dressings and other types of wound healing technologies are experiencing fast-paced development and rapid growth. As the population ages, demand will continue to rise for advanced dressings used to treat chronic wounds, such as pressure ulcers, venous stasis ulcers, and diabetic ulcers. Moist wound dressings, which facilitate natural wound healing in a cost-effective manner, will be increasingly important. In commercially available hydrogel / gauze wound dressings the gel swells to adsorb wound excreta and provide an efficient non adhesive particle barrier. An alternative to hydrogels are microgels. Essentially discrete colloidal gel particles, as a result of their very high surface area to volume ratio compared to bulk gels, they have a much faster response to external stimuli such as temperature or pH. In response to either an increase or decrease in solvent quality these porous networks shrink and swell reversibly. When swollen the interstitial regions within the polymer matrix are available for further chemistry; such as the incorporation of small molecules. The reversible shrinking and swelling as a function of external stimuli provides a novel drug release system. As the environmental conditions of a wound change over its lifetime, tending to increase in pH if there is an infection combining these discrete polymeric particles with a substrate such as cotton, results in a smart wound dressing.