Displaying publications 1 - 20 of 31 in total

  1. Hu J, Neoh KB, Appel AG, Lee CY
    PMID: 22085890 DOI: 10.1016/j.cbpa.2011.10.028
    The foraging patterns of termites are strongly related to physiological limits in overcoming desiccation stress. In this study, we examined moisture preferences and physiological characteristics of Macrotermes carbonarius (Hagen) and M. gilvus (Hagen) as both exhibit conspicuous patterns of foraging activity. Despite both species showing no significant differences in calculated cuticular permeability, and percentage of total body water, they differed greatly in rate of water loss and surface area to volume ratio. For example, M. carbonarius which had a lower surface area to volume ratio (29.26-53.66) showed lower rate of water loss and percentage of total body water loss. This also resulted in higher LT(50) when exposed to extreme conditions (≈2% RH). However, contrasting observations were made in M. gilvus that has smaller size with higher surface area to volume ratio of 40.28-69.75. It is likely that the standard equation for calculating insect surface areas is inadequate for these termite species. The trend was further supported by the result of a moisture preference bioassay that indicated M. carbonarius had a broader range of moisture preference (between 5% and 20%) than M. gilvus which had a relatively narrow moisture preference (only 20%). These results explain why M. carbonarius can tolerate desiccation stress for a longer period foraging above-ground in the open air; while M. gilvus only forages below ground or concealed within foraging mud tubes.
  2. Neoh KB, Hu J, Yeoh BH, Lee CY
    Pest Manag Sci, 2012 May;68(5):749-56.
    PMID: 22076820 DOI: 10.1002/ps.2322
    The effectiveness of chlorantraniliprole and other insecticides (bifenthrin, fipronil, indoxacarb, imidacloprid and chlorfenapyr) were tested against Coptotermes gestroi (Wasmann). Four experiments were conducted: a topical bioassay, a horizontal transfer study, an insecticide bioavailability test and a feeding bioassay.
  3. Choi JR, Hu J, Feng S, Wan Abas WA, Pingguan-Murphy B, Xu F
    Biosens Bioelectron, 2016 May 15;79:98-107.
    PMID: 26700582 DOI: 10.1016/j.bios.2015.12.005
    Lateral flow assays (LFAs) have currently attracted broad interest for point-of-care (POC) diagnostics, but their application has been restricted by poor quantification and limited sensitivity. While the former has been currently solved to some extent by the development of handheld or smartphone-based readers, the latter has not been addressed fully, particularly the potential influences of environmental conditions (e.g., temperature and relative humidity (RH)), which have not yet received serious attention. The present study reports the use of a portable temperature-humidity control device to provide an optimum environmental requirement for sensitivity improvement in LFAs, followed by quantification by using a smartphone. We found that a RH beyond 60% with temperatures of 55-60°C and 37-40°C produced optimum nucleic acid hybridization and antigen-antibody interaction in LFAs, respectively representing a 10-fold and 3-fold signal enhancement over ambient conditions (25°C, 60% RH). We envision that in the future the portable device could be coupled with a fully integrated paper-based sample-to-answer biosensor for sensitive detection of various target analytes in POC settings.
  4. Hu J, Wang S, Wang L, Li F, Pingguan-Murphy B, Lu TJ, et al.
    Biosens Bioelectron, 2014 Apr 15;54:585-97.
    PMID: 24333570 DOI: 10.1016/j.bios.2013.10.075
    Advanced diagnostic technologies, such as polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), have been widely used in well-equipped laboratories. However, they are not affordable or accessible in resource-limited settings due to the lack of basic infrastructure and/or trained operators. Paper-based diagnostic technologies are affordable, user-friendly, rapid, robust, and scalable for manufacturing, thus holding great potential to deliver point-of-care (POC) diagnostics to resource-limited settings. In this review, we present the working principles and reaction mechanism of paper-based diagnostics, including dipstick assays, lateral flow assays (LFAs), and microfluidic paper-based analytical devices (μPADs), as well as the selection of substrates and fabrication methods. Further, we report the advances in improving detection sensitivity, quantification readout, procedure simplification and multi-functionalization of paper-based diagnostics, and discuss the disadvantages of paper-based diagnostics. We envision that miniaturized and integrated paper-based diagnostic devices with the sample-in-answer-out capability will meet the diverse requirements for diagnosis and treatment monitoring at the POC.
  5. Feng X, Jiang G, Xia Z, Hu J, Wan X, Gao JM, et al.
    Org. Lett., 2015 Sep 18;17(18):4428-31.
    PMID: 26315849 DOI: 10.1021/acs.orglett.5b02046
    The first enantioselective synthesis of (-)-conolutinine was achieved in 10 steps. The synthesis featured a catalytic asymmetric bromocyclization of tryptamine to forge the tricycle intermediate. Hydration of an alkene catalyzed by Co(acac)2 was also employed as a key step to diastereoselectively introduce the tertiary alcohol moiety. The absolute configuration of (-)-conolutinine was established to be (2S,5aS,8aS,13aR) based on this asymmetric total synthesis.
  6. Choi JR, Hu J, Gong Y, Feng S, Wan Abas WA, Pingguan-Murphy B, et al.
    Analyst, 2016 05 10;141(10):2930-9.
    PMID: 27010033 DOI: 10.1039/c5an02532j
    Lateral flow assays (LFAs) have been extensively explored in nucleic acid testing (NAT) for medical diagnostics, food safety analysis and environmental monitoring. However, the amount of target nucleic acid in a raw sample is usually too low to be directly detected by LFAs, necessitating the process of amplification. Even though cost-effective paper-based amplification techniques have been introduced, they have always been separately performed from LFAs, hence increasing the risk of reagent loss and cross-contaminations. To date, integrating paper-based nucleic acid amplification into colorimetric LFA in a simple, portable and cost-effective manner has not been introduced. Herein, we developed an integrated LFA with the aid of a specially designed handheld battery-powered system for effective amplification and detection of targets in resource-poor settings. Interestingly, using the integrated paper-based loop-mediated isothermal amplification (LAMP)-LFA, we successfully performed highly sensitive and specific target detection, achieving a detection limit of as low as 3 × 10(3) copies of target DNA, which is comparable to the conventional tube-based LAMP-LFA in an unintegrated format. The device may serve in conjunction with a simple paper-based sample preparation to create a fully integrated paper-based sample-to-answer diagnostic device for point-of-care testing (POCT) in the near future.
  7. Choi JR, Hu J, Wang S, Yang H, Wan Abas WA, Pingguan-Murphy B, et al.
    Crit Rev Biotechnol, 2017 Feb;37(1):100-111.
    PMID: 26912259
    Dengue endemic is a serious healthcare concern in tropical and subtropical countries. Although well-established laboratory tests can provide early diagnosis of acute dengue infections, access to these tests is limited in developing countries, presenting an urgent need to develop simple, rapid, and robust diagnostic tools. Point-of-care (POC) devices, particularly paper-based POC devices, are typically rapid, cost-effective and user-friendly, and they can be used as diagnostic tools for the prompt diagnosis of dengue at POC settings. Here, we review the importance of rapid dengue diagnosis, current dengue diagnostic methods, and the development of paper-based POC devices for diagnosis of dengue infections at the POC.
  8. Han H, Chou CC, Li R, Liu J, Zhang L, Zhu W, et al.
    Sci Rep, 2018 06 22;8(1):9566.
    PMID: 29934599 DOI: 10.1038/s41598-018-27724-3
    Chalocomoracin (CMR), one of the major secondary metabolites found in fungus-infected mulberry leaves, is a potent anticancer agent. However, its anticancer mechanism remains elusive. Here, we demonstrated the potent anti-tumor activity and molecular mechanism of CMR both in vitro and in vivo. We showed for the first time that CMR treatment markedly promoted paraptosis along with extensive cytoplasmic vacuolation derived from the endoplasmic reticulum, rather than apoptosis, in PC-3 and MDA-MB-231cell lines. Additional studies revealed that ectopic expression of Myc-PINK1 (PTEN-induced kinase 1), a key regulator of mitophagy, rendered LNCap cells susceptible to CMR-induced paraptosis, suggesting that the mitophagy-dependent pathway plays a crucial role in inducing paraptosis by activating PINK1. CMR treatment directly upregulated PINK1 and downregulated Alix genes in MDA-MB-231 and PC-3 cell lines. Furthermore, mitophagy signaling and paraptosis with cytoplasmic vacuolation could be blocked by antioxidant N-acetylcysteine (NAC), indicating the novel pathway was triggered by reactive oxygen species (ROS) production. An in vivo MDA-MB-231 xenograft tumor model revealed that CMR suppressed tumor growth by inducing vacuolation production through the same signal changes as those observed in vitro. These data suggest that CMR is a potential therapeutic entity for cancer treatment through a non-apoptotic pathway.
  9. Hu J, Lin S, Tan BK, Hamzah SS, Lin Y, Kong Z, et al.
    Food Res Int, 2018 09;111:265-271.
    PMID: 30007685 DOI: 10.1016/j.foodres.2018.05.042
    Burkholderia cepacia (B. cepacia) is an aerobic Gram-negative bacillus found in various aquatic environments and can cause food contamination. We investigated the photodynamic antibacterial effects of food additive curcumin combined with EDTA on B. cepacia. We found a ~4-log reduction in B. cepacia viability when photo-irradiated with curcumin at 50 μM by blue LED light (16 mW/cm2) for 30 min with 0.4% (w/v) EDTA. Moreover, the bacterial morphological alterations and the leakage of intracellular contents were observed after photodynamic treatment. There were also obvious genomic DNA cleavage and a general loss of bacterial proteins assigned to large-scale protein degradation after photodynamic inactivation treatment. Collectively, curcumin in combination with EDTA illuminated by blue LED is a potential candidate for photodynamic inactivation of B. cepacia.
  10. Hu J, Chan LF, Souza RP, Tampakeras M, Kennedy JL, Zai C, et al.
    Neurosci Lett, 2014 Jan 24;559:39-43.
    PMID: 24275212 DOI: 10.1016/j.neulet.2013.11.025
    Evidence has shown that attempted suicide in psychiatric disorders is a complex interplay of genes and environment. Noradrenergic dysfunction due to abnormalities in the tyrosine hydroxylase (TH) gene has been implicated in the pathogenesis of suicidal behavior in mood disorders. However, suicide is a leading cause of mortality in schizophrenia too. Recent evidence suggests that TH gene variants may also increase the risk of suicide attempts in schizophrenia patients, although the interaction with established clinical risk factors is unclear. This study aimed to identify TH gene variants conferring risk for suicide attempt in schizophrenia while accounting for the interaction between this gene and clinical risk factors. We performed analysis on four TH SNPs (rs11564717, rs11042950, rs2070762, rs689) and the common TCAT repeat (UniSTS:240639) for 234 schizophrenia patients (51 suicide attempters and 183 non-attempters). Clinical risk factors and ethnic stratification were included as covariates. Single marker analysis identified the SNP rs11564717 (p=0.042) and the TCAT(6) (p=0.004) as risk variants for suicide attempt. We also identified the haplotype A-A-A-G as a risk factor for suicide attempt (p=0.0025). In conclusion, our findings suggest that TH polymorphisms may contribute to the risk of attempted suicide in schizophrenia even after accounting for established clinical risk factors and ethnic stratification. Further larger scale studies are needed to confirm these findings and to understand the mechanisms underlying the role of TH gene variants in suicide attempt in schizophrenia.
  11. Wang Z, Hu J, Hamzah SS, Ge S, Lin Y, Zheng B, et al.
    J Agric Food Chem, 2019 Jan 30;67(4):1092-1103.
    PMID: 30621393 DOI: 10.1021/acs.jafc.8b05281
    In this study, the antiobesity effects of n-butanol extract of lotus seeds (LBE) were evaluated in cultured 3T3-L1 preadipocytes and in high-fat diet (HFD)-fed mice. LBE decreased lipid contents in mature 3T3-L1 cells without obvious cytotoxicity. Meanwhile, LBE supplementation also led to weight loss and improved plasma lipid profiles in HFD-fed mice. Furthermore, LBE could activate AMP-activated protein kinase (AMPK) accompanied by down-regulation of lipogenesis related genes (PPARγ, aP2, LPL, C/EBPα, FAS, SREBP-1c) and up-regulation of lipolysis genes (adiponectin and PPARα) in vitro and in vivo. Collectively, our data demonstrated LBE possesses antiadipogenic and antilipogenic activities which are, at least partially, mediated by the activation of AMPK signaling pathways.
  12. Lin Y, Hu J, Li S, Hamzah SS, Jiang H, Zhou A, et al.
    Molecules, 2019 Jun 27;24(13).
    PMID: 31252525 DOI: 10.3390/molecules24132374
    Fresh-cut fruits and vegetables are the main sources of foodborne illness outbreaks with implicated pathogens such as Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes. This study aimed at investigating the influence of two key parameters (concentration of curcumin and illumination time) on the effects of curcumin-based photodynamic sterilization on the preservation of fresh-cut Hami melons. The results indicated that illumination with 50 μmol/L curcumin for 60 min using a blue LED lamp reduced the total aerobic microorganism count by ~1.8 log CFU/g in fresh-cut Hami melons. Besides this, the effects of photodynamic sterilization on the soluble solids content, color, water content, firmness, and sensory indices of the fresh-cut Hami melons were also evaluated. Compared to the control group, photodynamic sterilization can effectively delay the browning rate and maintain the luminosity, firmness, water content, and soluble solids content of fresh-cut Hami melon. The sensory quality was indeed preserved well after 9 days of storage in a fridge. These results showed that photodynamic sterilization is an effective and promising technology to prolong the shelf life of fresh-cut Hami melons.
  13. Lai D, Zhou A, Tan BK, Tang Y, Sarah Hamzah S, Zhang Z, et al.
    Food Chem, 2021 Nov 01;361:130117.
    PMID: 34058659 DOI: 10.1016/j.foodchem.2021.130117
    To overcome the poor water solubility of curcumin, a curcumin-β-cyclodextrin (Cur-β-CD) complex was prepared as a novel photosensitizer. Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to verify the formation of Cur-β-CD. Furthermore, the ROS generation capacity and photodynamic bactericidal effect were measured to confirm this Cur-β-CD complex kept photodynamic activity of curcumin. The result showed Cur-β-CD could effectively generate ROS upon blue-light irradiation. The plate count assay demonstrated Cur-β-CD complex possess desirable photodynamic antibacterial effect against food-borne pathogens including Staphylococcus aureus, Listeria monocytogenes and Escherichia coli. The cell morphology determined by scanning electron microscope (SEM) and transmission electron microscope (TEM) showed Cur-β-CD could cause cell deformation, surface collapse and cell structure damage of the bacteria, resulting in the leakage of cytoplasmic; while agarose gel electrophoresis and SDS-PAGE further illustrated the inactivation mechanisms by Cur-β-CD involve bacterial DNA damage and protein degradation.
  14. Lai D, Zhou F, Zhou A, Hamzah SS, Zhang Y, Hu J, et al.
    Carbohydr Polym, 2022 Apr 15;282:119112.
    PMID: 35123747 DOI: 10.1016/j.carbpol.2022.119112
    In this study, a biodegradable photodynamic antibacterial film (Car-Cur) was prepared using casting method with κ-Carrageenan (κ-Car) as film-forming substrate and curcumin-β-cyclodextrin (Cur-β-CD) complex as photosensitizer. The comprehensive performance of this Car-Cur film was investigated. The obtained results showed that the concentration of Cur-β-CD was an important factor determining the properties of film including tensile strength (TS) elongation at break (EB), water vapor permeability (WVP), water content (WC) and thermal stability. When the concentration of Cur-β-CD is 1%, the film demonstrated the maximum TS and EB, increased thermal stability, with desirable WVP and WC. Furthermore, this film also showed good photodynamic antibacterial potential against Staphylococcus aureus and Escherichia coli upon irradiation of blue LED light. Moreover, the film can be degraded in the soil in one week. In conclusion, our results suggested Car-Cur photodynamic film could be developed as biodegradable antimicrobial packaging material for food preservation.
  15. Zhou F, Lin S, Zhang J, Kong Z, Tan BK, Hamzah SS, et al.
    Photodiagnosis Photodyn Ther, 2021 Dec 08;37:102677.
    PMID: 34890782 DOI: 10.1016/j.pdpdt.2021.102677
    BACKGROUND: Pseudomonas aeruginosa (P. aeruginosa) is an emerging opportunistic pathogen, which can cause bacterial skin diseases such as green nail syndrome, interdigital infections and folliculitis. Curcumin-mediated antimicrobial photodynamic therapy (aPDT) has been demonstrated as a promising therapeutic option for the treatment of skin infection though its inactivation of gram-negative bacteria such as P. aeruginosa.

    MATERIALS AND METHODS: In the present study, we examined the adjuvant effect of polymyxin B on the antibacterial activity of curcumin-mediated aPDT against P. aeruginosa. P. aeruginosa was treated with curcumin in the presence of 0.1-0.5 mg/L polymyxin B and irradiated by blue LED light (10 J/cm2). Bacterial cultures treated with curcumin alone served as controls. Colony forming units (CFU) were counted and the viability of P. aeruginosa was calculated after aPDT treatment. The possible underlying mechanisms for the enhanced killing effects were also explored.

    RESULTS: The killing effects of curcumin-mediated aPDT against P. aeruginosa was significantly enhanced by polymyxin B (over 2-log reductions). Moreover, it was also observed that addition of polymyxin B in the curcumin-mediated aPDT led to the apparent bacterial membrane damage with increased leakage of cytoplasmic contents and extensive DNA and protein degradation.

    DISCUSSION: The photodynamic action of curcumin against P. aeruginosa could be significantly enhanced by the FDA-approved drug polymyxin B. Our results highlight the potential of introducing polymyxin B to enhance the effects of aPDT treatment against gram-negative skin infections, in particular, P. aeruginosa.

  16. Tang R, Yang H, Choi JR, Gong Y, Hu J, Feng S, et al.
    Talanta, 2016 May 15;152:269-76.
    PMID: 26992520 DOI: 10.1016/j.talanta.2016.02.017
    Lateral flow assays (LFAs) hold great promise for point-of-care testing, especially in resource-poor settings. However, the poor sensitivity of LFAs limits their widespread applications. To address this, we developed a novel device by integrating dialysis-based concentration method into LFAs. The device successfully achieved 10-fold signal enhancement in Human Immunodeficiency Virus (HIV) nucleic acid detection with a detection limit of 0.1nM and 4-fold signal enhancement in myoglobin (MYO) detection with a detection limit of 1.56ng/mL in less than 25min. This simple, low-cost and portable integrated device holds great potential for highly sensitive detection of various target analytes for medical diagnostics, food safety analysis and environmental monitoring.
  17. Hu J, Yew CT, Chen X, Feng S, Yang Q, Wang S, et al.
    Talanta, 2017 Apr 01;165:419-428.
    PMID: 28153277 DOI: 10.1016/j.talanta.2016.12.086
    The identification and quantification of chemicals play a vital role in evaluation and surveillance of environmental health and safety. However, current techniques usually depend on costly equipment, professional staff, and/or essential infrastructure, limiting their accessibility. In this work, we develop paper-based capacitive sensors (PCSs) that allow simple, rapid identification and quantification of various chemicals from microliter size samples with the aid of a handheld multimeter. PCSs are low-cost parallel-plate capacitors (~$0.01 per sensor) assembled from layers of aluminum foil and filter paper via double-sided tape. The developed PCSs can identify different kinds of fluids (e.g., organic chemicals) and quantify diverse concentrations of substances (e.g., heavy metal ions) based on differences in dielectric properties, including capacitance, frequency spectrum, and dielectric loss tangent. The PCS-based method enables chemical identification and quantification to take place much cheaply, simply, and quickly at the point-of-care (POC), holding great promise for environmental monitoring in resource-limited settings.
  18. Wong LP, Wu Q, Hao Y, Chen X, Chen Z, Alias H, et al.
    Int Health, 2021 May 04.
    PMID: 33945613 DOI: 10.1093/inthealth/ihab023
    BACKGROUND: We aimed to investigate the association between institution trust and public responses to the coronavirus disease 2019 (COVID-19) outbreak.

    METHODS: An Internet-based, cross-sectional survey was administered on 29 January 2020. A total of 4393 adults ≥18 y of age and residing or working in the province of Hubei, central China were included in the study.

    RESULTS: The majority of the participants expressed a great degree of trust in the information and preventive instructions provided by the central government compared with the local government. Being under quarantine (adjusted odds ratio [OR] 2.35 [95% confidence interval {CI} 1.80 to 3.08]) and having a high institutional trust score (OR 2.23 [95% CI 1.96 to 2.53]) were both strong and significant determinants of higher preventive practices scores. The majority of study participants (n=3640 [85.7%]) reported that they would seek hospital treatment if they suspected themselves to have been infected with COVID-19. Few of the participants from Wuhan (n=475 [16.6%]) and those participants who were under quarantine (n=550 [13.8%]) expressed an unwillingness to seek hospital treatment.

    CONCLUSIONS: Institutional trust is an important factor influencing adequate preventive behaviour and seeking formal medical care during an outbreak.

  19. Zhu M, Kleepbua J, Guan Z, Chew SP, Tan JW, Shen J, et al.
    Healthcare (Basel), 2021 Sep 16;9(9).
    PMID: 34574997 DOI: 10.3390/healthcare9091220
    This observational study aims to investigate the early disease patterns of coronavirus disease 2019 (COVID-19) in Southeast Asia, consequently providing historical experience for further interventions. Data were extracted from official websites of the WHO and health authorities of relevant countries. A total of 1346 confirmed cases of COVID-19, with 217 recoveries and 18 deaths, were reported in Southeast Asia as of 16 March 2020. The basic reproductive number (R0) of COVID-19 in the region was estimated as 2.51 (95% CI:2.31 to 2.73), and there were significant geographical variations at the subregional level. Early transmission dynamics were examined with an exponential regression model: y = 0.30e0.13x (p < 0.01, R2 = 0.96), which could help predict short-term incidence. Country-level disease burden was positively correlated with Human Development Index (r = 0.86, p < 0.01). A potential early shift in spatial diffusion patterns and a spatiotemporal cluster occurring in Malaysia and Singapore were detected. Demographic analyses of 925 confirmed cases indicated a median age of 44 years and a sex ratio (male/female) of 1.25. Age may play a significant role in both susceptibilities and outcomes. The COVID-19 situation in Southeast Asia is challenging and unevenly geographically distributed. Hence, enhanced real-time surveillance and more efficient resource allocation are urgently needed.
  20. Choi JR, Liu Z, Hu J, Tang R, Gong Y, Feng S, et al.
    Anal Chem, 2016 06 21;88(12):6254-64.
    PMID: 27012657 DOI: 10.1021/acs.analchem.6b00195
    In nucleic acid testing (NAT), gold nanoparticle (AuNP)-based lateral flow assays (LFAs) have received significant attention due to their cost-effectiveness, rapidity, and the ability to produce a simple colorimetric readout. However, the poor sensitivity of AuNP-based LFAs limits its widespread applications. Even though various efforts have been made to improve the assay sensitivity, most methods are inappropriate for integration into LFA for sample-to-answer NAT at the point-of-care (POC), usually due to the complicated fabrication processes or incompatible chemicals used. To address this, we propose a novel strategy of integrating a simple fluidic control strategy into LFA. The strategy involves incorporating a piece of paper-based shunt and a polydimethylsiloxane (PDMS) barrier to the strip to achieve optimum fluidic delays for LFA signal enhancement, resulting in 10-fold signal enhancement over unmodified LFA. The phenomena of fluidic delay were also evaluated by mathematical simulation, through which we found the movement of fluid throughout the shunt and the tortuosity effects in the presence of PDMS barrier, which significantly affect the detection sensitivity. To demonstrate the potential of integrating this strategy into a LFA with sample-in-answer-out capability, we further applied this strategy into our prototype sample-to-answer LFA to sensitively detect the Hepatitis B virus (HBV) in clinical blood samples. The proposed strategy offers great potential for highly sensitive detection of various targets for wide application in the near future.
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