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  1. Mohd Daud N, Saeful Bahri IF, Nik Malek NA, Hermawan H, Saidin S
    Colloids Surf B Biointerfaces, 2016 Sep 01;145:130-9.
    PMID: 27153117 DOI: 10.1016/j.colsurfb.2016.04.046
    Chlorhexidine (CHX) is known for its high antibacterial substantivity and is suitable for use to bio-inert medical devices due to its long-term antibacterial efficacy. However, CHX molecules require a crosslinking film to be stably immobilized on bio-inert metal surfaces. Therefore, polydopamine (PDA) was utilized in this study to immobilize CHX on the surface of 316L type stainless steel (SS316L). The SS316L disks were pre-treated, modified with PDA film and immobilized with different concentrations of CHX (10mM-50mM). The disks were then subjected to various surface characterization analyses (ATR-FTIR, XPS, ToF-SIMS, SEM and contact angle measurement) and tested for their cytocompatibility with human skin fibroblast (HSF) cells and antibacterial activity against Escherichia coli and Staphylococcus aureus. The results demonstrated the formation of a thin PDA film on the SS316L surface, which acted as a crosslinking medium between the metal and CHX. CHX was immobilized via a reduction process that covalently linked the CHX molecules with the functional group of PDA. The immobilization of CHX increased the hydrophobicity of the disk surfaces. Despite this property, a low concentration of CHX optimized the viability of HSF cells without disrupting the morphology of adherent cells. The immobilized disks also demonstrated high antibacterial efficacy against both bacteria, even at a low concentration of CHX. This study demonstrates a strong beneficial effect of the crosslinked PDA film in immobilizing CHX on bio-inert metal, and these materials are applicable in medical devices. Specifically, the coating will restrain bacterial proliferation without suffocating nearby tissues.
  2. Ab Hamid F, Che Azemin MZ, Salam A, Aminuddin A, Mohd Daud N, Zahari I
    Curr. Eye Res., 2016 Jun;41(6):823-31.
    PMID: 26268475 DOI: 10.3109/02713683.2015.1056375
    PURPOSE: The goal of this study was to provide the empirical evidence of fractal dimension as an indirect measure of retinal vasculature density.

    MATERIALS AND METHODS: Two hundred retinal samples of right eye [57.0% females (n = 114) and 43.0% males (n = 86)] were selected from baseline visit. A custom-written software was used for vessel segmentation. Vessel segmentation is the process of transforming two-dimensional color images into binary images (i.e. black and white pixels). The circular area of approximately 2.6 optic disc radii surrounding the center of optic disc was cropped. The non-vessels fragments were removed. FracLac was used to measure the fractal dimension and vessel density of retinal vessels.

    RESULTS: This study suggested that 14.1% of the region of interest (i.e. approximately 2.6 optic disk radii) comprised retinal vessel structure. Using correlation analysis, vessel density measurement and fractal dimension estimation are linearly and strongly correlated (R = 0.942, R(2) = 0.89, p 

  3. Mohd Daud N, Hussein Al-Ashwal R, Abdul Kadir MR, Saidin S
    Ann. Anat., 2018 Nov;220:29-37.
    PMID: 30048761 DOI: 10.1016/j.aanat.2018.06.009
    Immobilization of chlorhexidine (CHX) on stainless steel 316L (SS316L), assisted by a polydopamine film as an intermediate layer is projected as an approach in combating infection while aiding bone regeneration for coating development on orthopedic and dental implants. This study aimed to investigate the ability of CHX coating to promote apatite layer, osteoblast cells viability, adhesion, osteogenic differentiation and mineralization. Stainless steel 316L disks were pre-treated, grafted with a polydopamine film and immobilized with different concentrations of CHX (10-30mM). The apatite layer formation was determined through an in vitro simulated body fluid (SBF) test by ATR-FTIR and SEM-EDX analyses. The osteoblastic evaluations including cells viability, cells adhesion, osteogenic differentiation and mineralization were assessed with human fetal osteoblast cells through MTT assay, morphology evaluation under FESEM, ALP enzyme activity and Alizarin Red S assay. The apatite layer was successfully formed on the CHX coated disks, demonstrating potential excellent bioactivity property. The CHX coatings were biocompatible with the osteoblast cells at low CHX concentration (<20mM) with good adhesion on the metal surfaces. The increment of ALP activity and calcium deposition testified that the CHX coated disks able to support osteoblastic maturation and mineralization. These capabilities give a promising value to the CHX coating to be implied in bone regeneration area.
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