Tuneable Chitosan Particles with Potential Forensic and Pharmaceutical Applications

Chitosan(CS), a natural cationic polymer obtained by the partial N-deacetylation of chitin, has been investigated widely for its potential in the development of food and drug delivery systems and pharmaceutical applications, however it has not generally been considered in forensic applications for example fingerprints (fingermarks). The purpose of this study was to prepare chitosan micro/nanoparticles through cross-linking with tripolyphosphate (TPP) utilising the ionotropic interaction between positively charged amino groups (CS) and negatively charged counter ions (TPP). The investigation into the potential of these particles was divided into two parts: forensic and pharmaceutical applications. Firstly, these formulations were characterized (relative viscosity, zeta potential, particle size, FT-IR, XRD, SEM) and evaluated for forensic applications (fingermark visualisation). This can be controlled by the charge density of CS and TPP, which depends on the pH and ionic strength of the solution. Secondly, the combined effects of three independent variables (pH, ionic strength and CS: TPP ratio) on three important physico-chemical properties (viscosity, zeta potential andparticle size) during the preparation of microparticles were investigated. CS: TPP microparticles (CSMPs) were prepared using experimental design and equations were generated and used to predict relative viscosity, zeta potential and particle size under different conditions. This gives us the ability to design tuneable CS: TPP microparticles with desired size for specific pharmaceutical or forensic applications e.g. latent fingerprint visualisation. Fingerprints are a very common form of physical evidence. The most commonly used procedure for revealing the ridge pattern is powder dusting, which relies on the mechanical adherence of fingerprint formulation to the fatty components of the skin deposit that are secreted by sweat pores that exist on friction ridges. The development of latent fingermarks using IICSMPs was analysed by using a 23 factorial design, which considered simultaneously three main factors: pH, ionic strength and CS: TPP (v/v) ratio. CS: TPP ratio has the strongest effect on fingerprint quality. The best conditions for fingerprint visualisation were microparticles prepared using a buffer of pH 4.8, 0.2 M ionic strength at a CS: TPP of 2:1. Although we have demonstrated that CSMPs can be used to develop latent fingermarks there are limitationsin that they are only applicable as a powder and are only sensitive up to the third depletion level for a fingermark aged for one day. In the final sections of this thesis, chitosan nanoparticles were prepared and characterized for potential applications in drug delivery (using ibuprofen as a model drug) and in terms of their interactions with mucin (mucoadhesion). It has been demonstrated that chitosan nanoparticles can incorporate appreciable quantities of ibuprofen into nanoparticles (CS-IBU-TPP), although the order addition of the individual components is important. The carboxylate ions of the ibuprofen (negative charge) and could bind strongly to the ammonium group (positive charge) of chitosan, thereby allowing greater drug-loading capacity in the chitosan nanoparticles. In addition, the interaction between different ratios chitosan nanoparticles (CS: TPP) and mucin were evaluated based on relative viscosity, zeta potential and particle size. It has been suggested that chitosan nanoparticle-mucin interactions are driven by electrostatic forces. The results conclude that interactions between CS: TPP nanoparticles and mucin occur, with a CS: TPP ratio of 4:1 displaying the strongest interaction with mucin. This is observed through differences in relative viscosity, zeta potential and particle size

The potential of chitosan-tripolyphosphate microparticles in the visualisation of latent fingermarks

Chitosan (CS) is a cationic polymer with excellent film, gel and particle-forming properties. This polymer has been investigated widely for its potential in the development of food and drug delivery systems and pharmaceutical applications, however it has not generally been considered in forensic applications for example fingerprints (fingermarks). Fingerprints are a very common form of physical evidence. The most commonly used procedure for revealing the ridge pattern is powder dusting, which relies on the mechanical adherence of fingerprint formulation to the fatty components of the skin deposit that are secreted by sweat pores that exist on friction ridges. Cross-linking between oppositely charged molecules can be used to prepare chitosan microparticles. Tripolyphosphate (TPP) is a nontoxic polyanion; it can form particles by ionic interaction between positively charged amino groups of CS and negatively charged counter ions of TPP. In the present study chitosan microparticles (CSMPs) were prepared under four different processing/formulation conditions. The development of latent fingermarks using CSMPs was analysed by using a 23 factorial design, which considered simultaneously three main factors: pH, ionic strength and CS: TPP (v/v) ratio. In this study CS: TPP ratio has the strongest effect on fingerprint quality. The best conditions for fingerprint visualisation were pH 4.8, CS: TPP of 2:1 and 0.2 M of ionic strength in buffer (AB-12)

Abrasive water jet drilling of advanced sustainable bio-fibre-reinforced polymer/hybrid composites : a comprehensive analysis of machining-induced damage responses

This paper aims at investigating the effects of variable traverse speeds on machining-induced damage of fibre-reinforced composites, using the abrasive water jet (AWJ) drilling. Three different types of epoxy-based composites laminates fabricated by vacuum bagging technique containing unidirectional (UD) flax, hybrid carbon-flax and carbon fibre-reinforced composite were used. The drilling parameters used were traverse speeds of 20, 40, 60 and 80 mm/min, constant water jet pressure of 300 MPa and a hole diameter of 10 mm. The results obtained depict that the traverse speed had a significant effect with respect to both surface roughness and delamination drilling-induced damage responses. Evidently, an increase in water jet traverse speed caused an increase in both damage responses of the three samples. Significantly, the CFRP composite sample recorded the lowest surface roughness damage response, followed by C-FFRP, while FFRP exhibited the highest. However, samples of FFRP and hybrid C-FFRP recorded lowest and highest delamination damage responses, respectively. The discrepancy in both damage responses, as further validated with micrographs of colour video microscopy (CVM), scanning electron microscopy (SEM) and X-ray micro-computed tomography (X-ray μCT), is attributed to the different mechanical properties of the reinforced fibres, fibre orientation/ply stacking and hybridisation of the samples.Peer reviewe

Designing chitosan-tripolyphosphate microparticles with desired size for specific pharmaceutical or forensic applications

Chitosan (CS) is a natural cationic polymer obtained by the partial N-deacetylation of chitin. Chitosan microparticles can be prepared by cross-linking with tripolyphosphate (TPP) via the ionic interaction between positively charged amino groups (CS) and negatively charged counter ions (TPP). This can be controlled by the charge density of CS and TPP, which depend on the pH and ionic strength of the solution. The purpose of this study is to investigate the combined effects of three independent variables (pH, ionic strength and CS: TPP ratio) on three important physico-chemical properties (viscosity, zeta potential and particle size) during the preparation of microparticles. CS: TPP microparticles were prepared using experimental design and equations were generated and used to predict relative viscosity, zeta potential and particle size under different conditions. This gives us the ability to design tuneable CS-TPP microparticles with desired size for specific pharmaceutical or forensic applications e.g. latent fingerprint visualisation

Use of non‐LDL‐C lipid‐lowering medications in patients with type 2 diabetes

BackgroundA number of non-low-density lipoprotein cholesterol lipid abnormalities are associated with type 2 diabetes and insulin resistance, which may lead practitioners to use medications targeting these abnormal lipid fractions despite a lack of evidence or guideline recommendations.Methods and resultsAmong 382 921 US patients with type 2 diabetes (69% with cardiovascular disease, 76% on a statin), 95 995 (26%) were on some nonstatin lipid-lowering medication-19 265 (5%) on niacin, 32 919 (9%) on a fibrate and 69 513 (18%) on fish oil. Use of all three medications was stable over time and higher in patients with cardiovascular disease and with higher triglyceride levels, although even among patients with triglyceride levels <2.3 mmol/L, 6% were on a fibrate and 17% were on fish oil.ConclusionAs clinical trials demonstrate little to no cardiovascular benefit from taking these medications, greater attention is needed to focus the use of lipid-lowering medications to those with proven benefit