Rahimah Othman
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Preferred name
Rahimah Othman
Official Name
Rahimah, Othman
Alternative Name
Othman, Rahimah
Othman, R.
Main Affiliation
Scopus Author ID
24348849600
Researcher ID
DWI-3419-2022

Research Output
Now showing 1 - 5 of 5
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Light-induced reversible destabilization of responsive latex particles prepared via high solids content emulsion polymerization

2023 , Thiago R. Guimarães , Rahimah Othman , Robert McKenzie , Yutaka Takahashi , Yukishige Kondo , Per B. Zetterlund

Aqueous dispersions of polymer nanoparticles (latexes) are of high commercial importance — it can be desirable to reversibly destabilize such latexes, for example, to enable transport/storage without the significant weight fraction of the water. In the present work, we have employed ab initio emulsion polymerization of methyl methacrylate with industrially relevant high solids content using mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the photo-switchable cationic surfactant 2-(4-(4-butylphenyl)diazenylphenoxy)ethyltrimethylammonium bromide (C4AzoTAB). C4AzoTAB contains an azobenzene moiety that can undergo trans–cis isomerization triggered by UV light, the cis form being a less effective surfactant than the trans form. Rapid destabilization (sedimentation) could be achieved on exposure of the diluted latex to UV light using a continuous flow device, and subsequent redispersion was obtained on exposure to visible light, demonstrating reversibility of the process. The presence of the anionic SDS as well as judicious choice of the amphoteric initiator VA-057 play key roles in designing successful destabilization, with latex pH being of crucial importance.

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Preparation of biodegradable polymeric nanoparticles for pharmaceutical applications using glass capillary microfluidics

2015 , Rahimah Othman , Goran T. Vladisavljević , Zoltan K. Nagy

The aim of this study was to develop a new microfluidic approach for the preparation of nanoparticles with tuneable sizes based on micromixing/direct nanoprecipitation in a coaxial assembly of tapered-end glass capillaries. The organic phase was 1 wt% poly(ε-caprolactone) (PCL) or poly(dl-lactic acid) (PLA) in tetrahydrofuran and the antisolvent was Milli-Q water. The size of nanoparticles was precisely controlled over a range of 190–650 nm by controlling phase flow rates, orifice size and flow configuration (two- phase co-flow or counter-current flow focusing). Smaller particles were produced in a flow focusing device, because the organic phase stream was significantly narrower than the orifice and remained narrow for a longer distance downstream of the orifice. The mean size of PCL particles produced in a flow focusing device with an orifice size of 200 μm, an organic phase flow rate of 1.7 mL h 1 and an aqueous-to-organic flow rate ratio of 10 was below 200 nm. The size of nanoparticles decreased with decreasing the orifice size and increasing the aqueous-to-organic phase flow rate ratio. Due to higher affinity for water and amorphous structure, PLA nanoparticles were smaller and exhibited a smoother surface and more rounded hape than PCL particles.

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Intensification of antioxidant-rich extract from Moringa Oleifera leaves using different solvents: optimization and characterization

2023 , Monisha Devi Elan Solan Marimuthu , Rahimah Othman , Siti Pauliena Mohd Bohari , Wei Jinn Ooi

Natural antioxidants have gained a huge amount of interest due to their ability to combat devastating ailments such as obesity and hypercholesterolemia. Rich in phenolics and flavonoids, Moringa Oleifera (MO) has piqued the interest of many researchers. MO plants have numerous nutritional and therapeutic advantages. The current study aims to maximize yield by optimizing the conditions of MO leaves extraction with the help of a few organic second solvents. Central Composite Design (CCD) of Response Surface Methodology (RSM) was used to optimize total phenolic content (TPC) and total flavonoid content (TFC) of MO extract. Four independent variables (A) type of second solvents, (B) solvent to second solvent ratio, (C) extraction temperature, and (D) extraction time were studied. TPC was evaluated using the Folin–Ciocalteu colorimetric technique, and extract solutions were measured at 765 nm. TFC was determined by aluminium chloride colorimetric test at wavenumber of 416 nm. The functional group of the optimized MO extract was subsequently studied using Fourier Transform Infrared Spectroscopy (FTIR). The optimization studies indicated that the optimum TPC was 313.265 µg · GAE ·mg−1 and TFC was 90.268 µg · QE · mg−1 which were achieved at formulation conditions of (A) acetone, (B) at 1:3, (C) of 100 °C, and (D) of 240 min. The most intense stretching peak of FTIR spectra was detected at 3262.79 cm−1 revealed the characteristics absorption of hydroxyl groups from phenolic content of MO extract. This simulated finding proved that the best extraction solvent elucidates that MO leaves are rich in valuable antioxidants with tremendous therapeutic potency for obesity and hypercholestrolaemia treatment.

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Smart self-assembled polymeric-MMT/Moringa Oleifera L. particles by solvent replacement method

2024-10 , Rahimah Othman , Koh Qi Sheng , Mohd Irfan Hatim Mohamed Dzahir , Monisha Devi , Siti Pauliena Mohd Bohari

Obesity, stemming from metabolic syndrome and energy imbalance, is a common health concern characterized by excess energy consumption and fat buildup. Moringa Oleifera L. (MO), known for its anti-obesity properties, is extracted via Soxhlet extraction. MO is extracted using the Soxhlet extraction method. To evaluate the antioxidant properties of MO powder, several analyses were conducted, including the assessment of total phenolic content (TPC), total flavonoid content (TFC), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) activity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity. The TPC and TFC, DPPH activity, and ABTS activity values were determined to be 386.7 mg GAE/g and 82.33 mg QE/g, 32.86 %, and 49.4 % respectively. To improve drug delivery, the freeze-dried MO powder was encapsulated within a polymeric carrier, poly(-caprolactone) (PCL). Moreover, the incorporation of montmorillonite (MMT) into the MO-loaded PCL nanoparticles enhanced the encapsulation efficiency and drug loading of MO. Nanoprecipitation was employed as a method to produce the nanoparticles, and the effects of four key parameters were studied: the ratio of aqueous phase volume to organic volume (1.5 – 10), stirring speed (400 rpm – 1200 rpm), mass weightage of MO (1 % -5 %), and mass weightage of MMT (2 % - 5 %). Design Expert was utilized for full factorial analysis to assess the impact of these parameters on encapsulation efficiency and drug loading. The optimal formulation was achieved at the ratio of aqueous phase volume to the organic volume of 1.5, stirring speed of 400 rpm, mass weightage of MO at 1 %, and mass weightage of MMT at 5% The expected encapsulation efficiency is 91.33 % and drug loading is 6.49 %.

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Incorporation of hybrid pre-dispersed organo-montmorillonite/destabilized bentonite nanofillers for improving tensile strength of PEVA copolymer with 40% vinyl acetate composition

2020 , Tuty Fareyhynn Mohammed Fitri , Azlin Fazlina Osman , Rahimah Othman , Zaleha Mustafa

In this work, soft and flexible poly (ethylene-co-vinyl acetate) (PEVA) with 40% vinyl acetate (VA) composition was used as matrix material to form nanocomposites with single nanofiller (organo-montmorillonite (OMMT) or Bentonite (Bent)) and hybrid nanofillers (OMMT+Bent in the ratios of 4:1, 3:2, 2:3 and 1:4). In order to achieve greater exfoliation and dispersion of the hybrid nanofillers in the PEVA matrix, the pre- dispersing and destabilization technique was applied to the O-MMT and Bent, respectively. The procedures were done prior to the melt compounding process of the nanocomposite. A tensile test was done to evaluate the mechanical properties of the resultant nanocomposites and to allow the selection of the best OMMT/Bent ratio for the production of the hybrid nanocomposite. The structure and fractured surfaces of the neat PEVA and nanocomposite were analyzed using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM), respectively. Results indicated that the addition of hybrid pre-dispersed OMMT/destabilized bentonite nanofillers into the PEVA matrix resulted in greater mechanical performance as compared to the single OMMT or single Bent nanofiller. The best achievement in the tensile strength and elongation at break of the PEVA hybrid nanocomposite was obtained when the hybrid nanofillers was added in the ratio of 4:1 (OMMT: Bent). The SEM analysis showed that the PEVA hybrid nanocomposite with 4OMMT: 1Bent had greater matrix deformation than the neat PEVA when subjected to tensile load. This mechanical deformation could be related to the increased flexibility of the PEVA chains which facilitated more energy absorption during the stretching of the material. Apparently, this mechanism acted as a matrix toughening process which allowed the increment of both tensile strength and elongation at break values of the PEVA upon the addition of the hybrid nanofillers.

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