Siti Hamimah Sheikh Abdul Kadir

Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes

Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm(-2)h(-1) to 95.36Lm(-2)h(-1) upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application.

Development of biocompatible and safe polyethersulfone hemodialysis membrane incorporated with functionalized multi-walled carbon nanotubes

A novel approach in the design of a safe, high performance hemodialysis membrane is of great demand. Despite many advantages, the employment of prodigious nanomaterials in hemodialysis membrane is often restricted by their potential threat to health. Hence, this work focusses on designing a biocompatible polyethersulfone (PES) hemodialysis membrane embedded with poly (citric acid)-grafted-multi walled carbon nanotubes (PCA-g-MWCNTs). Two important elements which could assure the safety of the nanocomposite membrane, i.e. (i) dispersion stability and (ii) leaching of MWCNTs were observed. The results showed the improved dispersion stability of MWCNTs in water and organic solvent due to the enriched ratio of oxygen-rich groups which subsequently enhanced membrane separation features. It was revealed that only 0.17% of MWCNTs was leached out during the membrane fabrication process (phase inversion) while no leaching was detected during permeation. In terms of biocompatibility, PES/PCA-g-MWCNT nanocomposite membrane exhibited lesser C3 and C5 activation (189.13 and 5.29ng/mL) and proteins adsorption (bovine serum albumin=4.5μg/cm2, fibrinogen=15.95μg/cm2) as compared to the neat PES membrane, while keeping a normal blood coagulation time. Hence, the PES/PCA-g-MWCNT nanocomposite membrane is proven to have the prospect of becoming a safe and high performance hemodialysis membrane.

Hemocompatibility evaluation of poly(1,8-octanediol citrate) blend polyethersulfone membranes

In this study, poly (1,8-octanediol citrate) (POC) was used to modify polyethersulfone (PES)-based membrane to enhance its hemocompatibility. Different compositions of POC (0-3%) were added into the polyethersulfone (PES) dope solutions and polyvinylpyrrolidone (PVP) was used as pore forming agent. The hemocompatible POC modified PES membranes were fabricated through phase-inversion technique. The prepared membranes were characterized using attenuated total reflectance-Fourier transform infrared (ATR-FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Atomic-force microscopy (AFM), contact angle, Zeta-potential, membrane porosity and pore size and pure water flux (PWF) and BSA rejection. The hemocompatibility of the modified PES membranes was evaluated by human serum fibrinogen (FBG) protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT) and prothrombin time (PT), and thrombin-antithrombin III (TAT), complement (C3a and C5a) activation and Ca2+ absorption on membrane. Results showed that by increasing POC concentration, FBG adsorption was reduced, less platelets adhesion, prolonged APTT and PT, lower TAT, C5a and C3a activation and absorb more Ca2+ ion. These results indicated that modification of PES with POC has rendered improved hemocompatibility properties for potential application in the field of blood purification, especially in hemodialysis.

Reduction of oxidative-nitrosative stress underlies anticataract effect of topically applied tocotrienol in streptozotocin-induced diabetic rats

Cataract, a leading cause of blindness, is of special concern in diabetics as it occurs at earlier onset. Polyol accumulation and increased oxidative-nitrosative stress in cataractogenesis are associated with NFκB activation, iNOS expression, ATP depletion, loss of ATPase functions, calpain activation and proteolysis of soluble to insoluble proteins. Tocotrienol was previously shown to reduce lens oxidative stress and inhibit cataractogenesis in galactose-fed rats. In current study, we investigated anticataract effects of topical tocotrienol and possible mechanisms involved in streptozotocin-induced diabetic rats. Diabetes was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin. Diabetic rats were treated with vehicle (DV) or tocotrienol (DT). A third group consists of normal, non-diabetic rats were treated with vehicle (NV). All treatments were given topically, bilaterally, twice daily for 8 weeks with weekly slit lamp monitoring. Subsequently, rats were euthanized and lenses were subjected to estimation of polyol accumulation, oxidative-nitrosative stress, NFκB activation, iNOS expression, ATP levels, ATPase activities, calpain activity and total protein levels. Cataract progression was delayed from the fifth week onwards in DT with lower mean of cataract stages compared to DV group (p<0.01) despite persistent hyperglycemia. Reduced cataractogenesis in DT group was accompanied with lower aldose reductase activity and sorbitol level compared to DV group (p<0.01). DT group also showed reduced NFκB activation, lower iNOS expression and reduced oxidative-nitrosative stress compared to DV group. Lenticular ATP and ATPase and calpain 2 activities in DT group were restored to normal. Consequently, soluble to insoluble protein ratio in DT group was higher compared to DV (p<0.05). In conclusion, preventive effect of topical tocotrienol on development of cataract in STZ-induced diabetic rats could be attributed to reduced lens aldose reductase activity, polyol levels and oxidative-nitrosative stress. These effects of tocotrienol invlove reduced NFκB activation, lower iNOS expression, restoration of ATP level, ATPase activities, calpain activity and lens protein levels.

Highly adsorptive oxidized starch nanoparticles for efficient urea removal

Portable dialysis is a need to implement daily and nocturnal hemodialysis. To realize portable dialysis, a dialysate regeneration system comprising superior adsorbents is required to regenerate the used dialysate. This study aims to develop a nano-adsorbent, derived from corn starch for urea removal. Oxidized starch nanoparticles (oxy-SNPs) were prepared via liquid phase oxidation, followed by chemical dissolution and non-solvent precipitation. The oxy-SNPs possessed Z-average size of 177.7 nm with carbonyl and carboxyl contents of 0.068 and 0.048 per 100 glucose units, respectively. The urea adsorption achieved the equilibrium after 4 h with 95% removal. The adsorption mechanism fitted Langmuir isotherm while the adsorption kinetics obeyed pseudo-second-order model. This new material has a maximum adsorption capacity of 185.2 mg/g with a rate constant of 0.04 g/mg.h. Moreover, the oxy-SNPs exhibited the urea uptake recovery of 91.6%. Oxy-SNPs can become a promising adsorbent for dialysate regeneration system to remove urea.

Kajian sifat morfologi membran fotopemangkin gentian berongga dwi lapisan TIO2/pvdf untuk penguraian sebatian pengganggu endokrin

Various Endocrine Disrupting Compounds (EDCs) either natural or synthetics have been identified including bisphenol A (BPA), dioxin, polychlorinated biphenyls, and dichlorodiphenyltrichloroethane (DDT). These compounds which present widely in the product of solvent industry, agricultural, pharmaceuticals and household convenience may directly or indirectly interrupt the normal function of endocrine system. Recently, the EDCs threats to human health have led to the increasing demand of clean water sources which excites a challenge for the contaminants removal processes. Conventional treatment methods may not completely remove the contaminants, meanwhile advanced oxidation process (AOPs) especially photocatalysis have been proven efficient in removing the contaminants. Even though photocatalysis is efficient in suspension of either nano-or microscale, the immobilizing TiO2 in the membrane matrix for catalyst separation purposes have decreased the adsorption of organic substances on the TiO2 surface with potential loss of TiO2 during long-time usage. This lead to the emerging in the exploration and fabrication of dual layer hollow fiber (DLHF) membrane for better performance of immobilized TiO2. Therefore, we exploit this fact to investigate the incorporation of photocatalysis into dual-layer hollow fiber membrane which are believed may improve the photocatalytic degradation and separation efficiency. The FESEM results showed that both layers are compatible with each other and there are no delamination found between layers. The presence of outer layer does not influence the surface roughness; however improve the hydrophilicity and membrane strength. Altogether, photocatalytic dual layer hollow fiber (DLHF) membrane was successfully fabricated using co-extrusion technique.

The Effect of Air Gap on the Morphological Properties of Psf/pvp90 Membrane for Hemodialysis Application

Membrane morphology plays an important role in achieving high flux and excellent uremic toxin removal for efficient hemodialysis therapy. Hemodialysis membrane morphology correlates to spinning parameters applied during fabrication of membrane. The effect of air gap on the morphology and liquid separation performance of the polysulfone (PSf) hemodialysis membrane is investigated. PSf hollow fibre membranes were prepared via dry-wet spinning process from dope solution comprises of 18 wt% PSf and 4.8 wt% polyvinylpyrrolidone in Nmethyl- 2-pyrrolidone. The membrane morphology was characterised using a scanning electron microscope (SEM) before tested with the ultrafiltration system to measure the pure water flux (PWF) and protein rejection using bovine serum albumin (BSA). SEM analysis revealed that the air gap does change the structure of the membranes due to the elongation stress because of the gravitational pull on the PSf hollow fibres. At low air gap (3 cm), the lower average pore size on the outer surface reduced the PWF while at high air gap (50 cm), the larger average pore size of membranes permitted water molecules to pass through easier and faster. It was observed that the PWF of the membrane increased significantly with air gap due to the increasing pore size. Membrane fabricated at 50 cm air gap obtained better PWF (28.45 Lm-2h-1) and protein rejection (94.47 %) compared to the membranes fabricated at 3 and 30 cm air gap. The effect of air gap enhanced the morphology and the performance of PSf membrane for hemodialysis application.

The Effect of Pca-g-mwcnts Loading on the Performance of Pes/mwcnts Hemodialysis Membrane

Membrane fouling is one of the biggest obstacles towards hemodialysis treatment. In this work, multi-walled carbon nanotubes (MWCNTs) are incorporated to enhance the hydrophilicity and antifouling property of polyethersulfone (PES) hemodialysis membrane. Prior to the mixing, surface functionalisation of MWCNTs was carried out to introduce a large hyperbranched poly (citric acid) (PCA) for better dispersion. PCA-grafted (g)- MWCNTs were prepared by grafting citric acid monohydrate onto the wall of purified MWCNTs. PCA-g- MWCNTs (0 - 0.2 wt%) were then dispersed in PES and polyvinylpyrrolidone blends. The membranes were spun at 50 cm air gap, characterised in terms of morphology and hydrophilic properties before tested for pure water flux (PWF) and protein rejection using bovine serum albumin (BSA). The results revealed that, compared to the neat PES membrane, the PES/MWCNTs membranes were more hydrophilic. The highest PWF (110.4 L m-2 h-1) was achieved by the membrane incorporated with 0.1 wt% PCA-g-MWCNTs. Same trend was observed for protein rejection, where up to 0.1 wt% loading of PCA-g-MWCNTs, the PES/MWCNTs membrane rejected 97.3 % of BSA compared to 88.2 % as obtained from the neat membrane. It was found that the PES/MWCNTs membranes possessed a greater PWF recovery ratio, proving that the membranes antifouling property was improved. The addition of PCA-g-MWCNTs in the membranes enhanced the hydrophilicity as well as the antifouling property of the PES membrane for hemodialysis application.

Ursodeoxycholic acid protects cardiomyocytes against cobalt chloride induced hypoxia by regulating transcriptional mediator of cells stress hypoxia inducible factor 1α and p53 protein

In hepatocytes, ursodeoxycholic acid (UDCA) activates cell signalling pathways such as p53, intracellular calcium ([Ca2+]i), and sphingosine‐1‐phosphate (S1P)‐receptor via Gαi‐coupled‐receptor. Recently, UDCA has been shown to protect the heart against hypoxia‐reoxygenation injury. However, it is not clear whether UDCA cardioprotection against hypoxia acts through a transcriptional mediator of cells stress, HIF‐1α and p53. Therefore, in here, we aimed to investigate whether UDCA could protect cardiomyocytes (CMs) against hypoxia by regulating expression of HIF‐1α, p53, [Ca2+]i, and S1P‐Gαi‐coupled‐receptor. Cardiomyocytes were isolated from newborn rats (0‐2 days), and hypoxia was induced by using cobalt chloride (CoCl2). Cardiomyocytes were treated with UDCA and cotreated with either FTY720 (S1P‐receptor agonist) or pertussis toxin (PTX; Gαi inhibitor). Cells were subjected for proliferation assay, beating frequency, QuantiGene Plex assay, western blot, immunofluorescence, and calcium imaging. Our findings showed that UDCA counteracted the effects of CoCl2 on cell viability, beating frequency, HIF‐1α, and p53 protein expression. We found that these cardioprotection effects of UDCA were similar to FTY720, S1P agonist. Furthermore, we observed that UDCA protects CMs against CoCl2‐induced [Ca2+]i dynamic alteration. Pharmacological inhibition of the Gαi‐sensitive receptor did not abolish the cardioprotection of UDCA against CoCl2 detrimental effects, except for cell viability and [Ca2+]i. Pertussis toxin is partially effective in inhibiting UDCA protection against CoCl2 effects on CM cell viability. Interestingly, PTX fully inhibits UDCA cardioprotection on CoCl2‐induced [Ca2+]i dynamic changes. We conclude that UDCA cardioprotection against CoCl2‐induced hypoxia is similar to FTY720, and its actions are not fully mediated by the Gαi‐coupled protein sensitive pathways. Ursodeoxycholic acid is the most hydrophilic bile acid and is currently used to treat liver diseases. Recently, UDCA is shown to have a cardioprotection effects; however, the mechanism of UDCA cardioprotection is still poorly understood. The current data generated were the first to show that UDCA is able to inhibit the activation of HIF‐1α and p53 protein during CoCl2‐induced hypoxia in cardiomyocytes. This study provides an insight of UDCA mechanism in protecting cardiomyocytes against hypoxia.