Key Engineering Materials Vol. 901

Abstract: Ocimum gratissimum L. leaf oil exhibited many pharmacological properties. This study aimed to formulate and evaluate the physical and chemical stability of O. gratissimum leaf oil nanoemulsion. O. gratissimum leaf oil was extracted by hydrodistillation. The major component of the essential oil eugenol, was analyzed by UV-Vis spectrophotometry. Nanoemulsions of O. gratissimum leaf oil were formulated using polysorbate 80, hyaluronic acid, poloxamer 188, and deionized water by phase inversion composition method. The hydrodynamic diameter, polydispersity index, and zeta potential value of O. gratissimum leaf oil nanoemulsion was evaluated by a dynamic light scattering technique. The %remaining of eugenol in the nanoemulsion was analyzed by UV-Vis spectrophotometry. The essential oil extracted from of O. gratissimum leaf oil was a clear, pale yellow color. The %yield of the essential oil was 0.15 ± 0.03% v/w. The size of the nanoemulsion was less than 106 nm. The polydispersity index of the nanoemulsion was ranging from 0.303 - 0.586 and the zeta potential value of the nanoemulsion was closely to zero, depending on the formulation component. O. gratissimum leaf oil at concentrations ranging from 0.002 - 0.012% v/v contained 35 - 41% of eugenol. The size of nanoemulsion was significantly decreased after storage at 4 °C, while significantly increased upon storage at 45 °C. The size of nanoemulsion stored at 30 °C did not significantly change. The %remaining of eugenol in the nanoemulsion was more than 90% after storage at 4 °C and 30 °C for 28 days. The percentage of eugenol remaining in the nanoemulsion stored at 45 °C was more than 85 - 90%, suggesting that the temperature affected the stability of eugenol in the nanoemulsion.

Abstract: This work aimed to investigate the effect of cisplatin (CDDP)/curcumin (Cur)-loaded polycaprolactone nanoparticles (PCL-NPs) on an oral epidermal carcinoma cell line. PCL-NPs were fabricated using nanoprecipitation method employing poly(vinyl alcohol) and polysorbate 80 as stabilizers. Two anticancer compounds, CDDP and Cur, were incorporated into the PCL-NPs by entrapment technique. The physical characteristics of the NPs were evaluated. The presence of the drugs on the NPs was ascertained using Attenuated total reflection Fourier-transformed infrared (ATR-FTIR) spectroscopy, and the drug content was quantified by indirect method using ultraviolet spectroscopy and inductive coupled plasma-mass spectroscopy. The cytotoxic effect was demonstrated using MTT assay and the synergistic effect of both drugs was calculated by the combination index method using CompuSyn^® software. The findings revealed that the PCL-NPs were less than 300 nm with narrow size distribution. The appropriate drug concentration for drug loading was 0.12 mg/mL of Cur and 0.02 mg/mL of CDDP, providing approximately 70% and 80% loading efficacy, respectively. The improved anticancer effect was observed in the cells treated with mixture of the drugs and the NPs loaded with dual drugs. Above all, CDDP/Cur-loaded PCL-NPs were successfully prepared. The delivery system exhibited good anticancer effect against oral cancer cells which may be attributed to the synergism effect of CDDP and Cur loaded on the NPs.

Abstract: The objective of this research is to evaluate the antimicrobial activity of Nanostructured Lipid Carriers (NLCs) loading violacein extract. The extract was tested for the antimicrobial activities against 3 strains of pathogenic bacteria; namely Cutibacterium acnes ATCC 6919, Staphylococcus aureus ATCC 6538 and Staphylococcus epidermidis ATCC 12228 by agar well diffusion assay. The result indicated that the violacein extract from Chromobacterium violaceum ATCC 12472 has strongest antibacterial effect against C. acnes, S. aureus and S. epidermidis with MIC values in range of 0.0146-0.4688 mg/mL with the lowest MBC value of 0.0146 mg/mL against C. acnes. Violacein extract loaded Nanostructured Lipid Carriers (NLCs) for anti-acne products were prepared by using melt-emulsification technique. The studied factors are the ratio of liquid lipid and solid lipid (LL:SL), surfactant concentration and sonication time. The Ratio of Oleic acid and Compritol^® 888 ATO (3:1) with Tween 20 (1.5% w/w) and sonication time of 10 minute (F8 formulation) are an optimizing condition for NLC-Base. The resulted formulations showed the NLC-Base had average particle size of 213.7±2.42 nm with a polydispersity index of 0.239±0.003 and Zeta potential of -26.6±0.45 mV. After that, violacein extract (2% w/w) was loaded into the NLCs (VIO-NLCs). Antibacterial activity of VIO-NLCs 2 % was determined by using agar dilution. The result showed that VIO-NLCs 2 % can inhibit the growth of C. acnes for 60 days during storage. Furthermore, VIO-NLCs 2 % can also act as S. aureus and S. epidermidis inhibitor within 30 days shelf life.

Abstract: This study aimed to prepare diclofenac sodium (DCF)–loaded nanostructured lipid carriers (NLCs) (DCF-loaded NLCs) for optimizing the NLCs by using the Box-Behnken design. A hot emulsification method using an ultrasonic probe was employed to prepare DCF-loaded NLCs. The active ingredient, solid lipid, oil, and emulsifier were DCF, glyceryl monostearate (GMS) (X₁), oleic acid (X₂), and polysorbate 80 (X₃), respectively. The DCF-loaded NLCs had particle sizes of 69.29–187.3 nm. The polydispersity index (PDI) was in the range of 0.216–0.516, indicating a relatively narrow size distribution. The zeta potential of all formulations revealed the negative charge and ranged between -26.0 and -42.13 mV. The percentage encapsulation efficiency (%EE) was 92.71%–104.21%. The responses of all model formulations were created and the optimized formulation was selected by Design-Expert® software. The optimal formulation was composed of 2 g GMS, 0.926 g oleic acid, and 2.724 g polysorbate 80. The particle size and PDI experimental values with the optimal formulation did not differ from those predicted and were within the 95% CI. Therefore, the Box-Behnken design could be efficient in formulating and optimizing DCF-loaded NLCs.

Abstract: Colonic drug delivery systems (CDDS) show several advantages for treatment of inflammatory bowel disease such as improving the clinical outcomes and minimizing side effects of corticosteroids. However, variation of the patient's gastrointestinal tract (GIT) in terms of transit time and pH causes the fluctuation of the drug releasing site in the GIT resulting in low therapeutic efficiency. Consequently, 3D-printing techniques have been applied for preparation of personalized colonic drug delivery systems in this study. Prednisolone was selected as a model drug and prepared in the form of a core tablet. Polylactic acid (PLA) and polyvinyl alcohol (PVA) were printed as a tablet housing and a drug control release plug, respectively. A two-factor full factorial model was utilized to design the experiment and partial least square regression (PLS) models were generated to reveal and predict drug release time of the system. From the results, only thickness of the PVA plug significantly affected the drug release at sampling times of 5, 6, 10, and 24 h. The relations between thickness of the plug and drug releases at 5, 6, and 10 h are quadratic but that of 24 h is linear. The relation between thickness of the plug and drug releases is quadratic. The drug could not be completely released in 24 h because the drug was entrapped by PVA gel. The search results show the possibility to utilize the PLS models to modify drug release time for individual patients. However, alteration of plug polymer is a suggestion to obtain complete drug release.

Abstract: The mechanism of annealing-induced amorphization of metallic glass is investigated in this study via molecular dynamics simulation. Spherical nucleuses of Cu–Ni–Al alloy with a face-centered cubic structure are embedded to simulate nanograins in Cu–Ni–Al amorphous alloy; subsequently, the material is annealed at different temperatures. The results show that the critical radius for nucleation at temperatures above the glass transition temperature (Tg) affected the behavior, grain growth, and annihilation of nanograins in the Cu–Ni–Al amorphous alloy during annealing. When the temperature increased, the critical radius for nucleation increased as well. This causes the small nanograins to annihilate quickly and the large nanograins to develop rapidly. When the annealing temperature is higher than Tg, part of the crystal nuclei, which is smaller than the critical radius, can be eliminated. The crystallinity of the metallic glass decreased, and the minimum crystallinity is attained after a period of annealing simulation. Subsequently, as the residual effective nanograins began developing, the crystallinity of the amorphous metal increased again. Therefore, the annealing duration time is critical to the crystallinity of the amorphous alloy after annealing.

Abstract: Sulfide was used as solid lubricant, and MoS₂ was popular. It was used industry as powder shape. Sulfur as oil additive; ZDDP, MoTDC were also well known. These composites make tribofilm which prevent seizure, scoring and some tribological troubles. In this paper, sulfides were synthesized by powder metallurgy technics. In addition, these sulfides were mixed with bronze powders and sintered as cylindrical specimen. As a result of the friction test in the lubricated condition, tribofilm were covered with specimen surface. By XPS observation, sulfides and oxides were detected on the specimen surface. In the test, additive was not contained in the lubricant because PAO as base oil was adapted. However, sulfide in the specimen affect the making the tribofilm, especially when bornite (Cu₅FeS₄) was used.

Abstract: Bipolar plate is the key component of proton exchange membrane fuel cells. Due to the factors of rapid and mass production, the stamping process is selected to manufacture the bipolar metal plates. First, the stress-strain curve is performed by universal material testing machine.The stress-strain curve is necessary for bipolar plate stamping simultion. The maximum forging load and effective stress distribution of bipolar plate stamping are determined by finite element analysis. Finally, the effect of the traditional crank stamping on the flatness and section thickness of stainless steel bipolar plate are observed by experiments.

Abstract: This paper used finite element analysis of metal forming to study the forging process and die design of aluminum alloy brake parts. According to the process parameters and die design, the brake parts were forged by experiment. First, the die design is based on the product size and considering parting line, draft angle, forging tolerance, shrinkage and scrap. Secondly, the finite element analysis of metal forming is used to simulate the forging process of aluminum alloy brake parts. Finally, the aluminum alloy brake levers with dimensional accuracy and surface hardness were forged.

Abstract: Surface topographies play a critical role in controlling friction, surface damage and transfer layer formation in engineering applications; hence understanding this is of great importance. In this work, experimental studies were carried out to understand the influence of surface topography on friction, scuffing and transfer layer formation in completely immersed lubricated sliding interactions. For this, sliding experiments were carried out in sphere on flat configuration using EN31 steel flats and Tungsten Carbide pin countersurface. Perpendicular and parallel surface topographies were induced onto the steel flats. Experiments were conducted at high normal loads of 1000N, 2000N and 3000N. The results show that Surface topography has a significant influence on the frictional response. When the topography directionality was perpendicular to the sliding direction, scuffing was observed only at a high load of 3000N. A ‘peak friction’ was also observed during the occurrence of scuffing. When the directionality in topography was parallel to sliding direction, scuffing and surface damage occurred from 2000N itself, accompanied by a high amount of transfer layer formation. This can be attributed to the directionality of parallel topography, which displaces away the lubricant during sliding interaction, creating metal-to-metal contact and hence leading to scuffing and higher transfer layer formation.