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Fulltext Role of Nanomaterials in the Fabrication of bioNEMS/MEMS for Biomedical Applications and towards Pioneering Food Waste Utilisation

Dahlan NA, Thiha A, Ibrahim F, Milić L, Muniandy S, Jamaluddin NF, et al.

Nanomaterials (Basel), 2022 Nov 16;12(22).
PMID: 36432311 DOI: 10.3390/nano12224025

bioNEMS/MEMS has emerged as an innovative technology for the miniaturisation of biomedical devices with high precision and rapid processing since its first R&D breakthrough in the 1980s. To date, several organic including food waste derived nanomaterials and inorganic nanomaterials (e.g., carbon nanotubes, graphene, silica, gold, and magnetic nanoparticles) have steered the development of high-throughput and sensitive bioNEMS/MEMS-based biosensors, actuator systems, drug delivery systems and implantable/wearable sensors with desirable biomedical properties. Turning food waste into valuable nanomaterials is potential groundbreaking research in this growing field of bioMEMS/NEMS. This review aspires to communicate recent progress in organic and inorganic nanomaterials based bioNEMS/MEMS for biomedical applications, comprehensively discussing nanomaterials criteria and their prospects as ideal tools for biomedical devices. We discuss clinical applications for diagnostic, monitoring, and therapeutic applications as well as the technological potential for cell manipulation (i.e., sorting, separation, and patterning technology). In addition, current in vitro and in vivo assessments of promising nanomaterials-based biomedical devices will be discussed in this review. Finally, this review also looked at the most recent state-of-the-art knowledge on Internet of Things (IoT) applications such as nanosensors, nanoantennas, nanoprocessors, and nanobattery.
Fulltext A novel microfluidic compact disc to investigate electrochemical property changes between artificial and real salivary samples mixed with mouthwashes using electrical impedance analysis

Thiha A, Ibrahim F, Joseph K, Petrović B, Kojić S, Dahlan NA, et al.

PLoS One, 2023;18(2):e0280381.
PMID: 36795661 DOI: 10.1371/journal.pone.0280381

Diagnosing oral diseases at an early stage may lead to better preventive treatments, thus reducing treatment burden and costs. This paper introduces a systematic design of a microfluidic compact disc (CD) consisting of six unique chambers that run simultaneously from sample loading, holding, mixing and analysis. In this study, the electrochemical property changes between real saliva and artificial saliva mixed with three different types of mouthwashes (i.e. chlorhexidine-, fluoride- and essential oil (Listerine)-based mouthwashes) were investigated using electrical impedance analysis. Given the diversity and complexity of patient's salivary samples, we investigated the electrochemical impedance property of healthy real saliva mixed with different types of mouthwashes to understand the different electrochemical property which could be a foundation for diagnosis and monitoring of oral diseases. On the other hand, electrochemical impedance property of artificial saliva, a commonly used moisturizing agent and lubricant for the treatment of xerostomia or dry mouth syndrome was also studied. The findings indicate that artificial saliva and fluoride-based mouthwash showed higher conductance values compared to real saliva and two other different types of mouthwashes. The ability of our new microfluidic CD platform to perform multiplex processes and detection of electrochemical property of different types of saliva and mouthwashes is a fundamental concept for future research on salivary theranostics using point-of-care microfluidic CD platform.
Fulltext Oral micro-electronic platform for temperature and humidity monitoring

Popović ŽV, Thiha A, Ibrahim F, Petrović BB, Dahlan NA, Milić L, et al.

Sci Rep, 2023 Dec 02;13(1):21277.
PMID: 38042878 DOI: 10.1038/s41598-023-48379-9

Intraoral theranostics, the integration of diagnostics and therapeutics within the oral cavity, is gaining significant traction. This pioneering approach primarily addresses issues like xerostomia (dry mouth), commonly resulting from cancer treatment, with a specific focus on monitoring temperature and humidity. This paper introduces the innovative Intra-Oral Portable Micro-Electronic (IOPM) fluidic theranostic device platform. It leverages conventional dental spoons by incorporating advanced sensors for precise measurements of oral temperature and humidity. Personalization options include a microfluidic chip and a tooth model, enabling targeted delivery of therapeutic agents to optimize treatment outcomes. The electronic control system simplifies the administration of fluid dosages, intelligently adjusted based on real-time oral cavity temperature and humidity readings. Rigorous experimental evaluations validate the platform's precision in delivering fluid volumes at predefined intervals. This platform represents a transformative advancement for individuals contending with oral health challenges such as xerostomia (dry mouth). Furthermore, it has the potential to elevate oral healthcare standards by providing advanced diagnostics and tailored therapeutic solutions, benefiting both patients and dental professionals alike.
Fulltext Risk and protective factors of drug abuse among adolescents: a systematic review

Nawi AM, Ismail R, Ibrahim F, Hassan MR, Manaf MRA, Amit N, et al.

BMC Public Health, 2021 Nov 13;21(1):2088.
PMID: 34774013 DOI: 10.1186/s12889-021-11906-2

BACKGROUND: Drug abuse is detrimental, and excessive drug usage is a worldwide problem. Drug usage typically begins during adolescence. Factors for drug abuse include a variety of protective and risk factors. Hence, this systematic review aimed to determine the risk and protective factors of drug abuse among adolescents worldwide.
METHODS: Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was adopted for the review which utilized three main journal databases, namely PubMed, EBSCOhost, and Web of Science. Tobacco addiction and alcohol abuse were excluded in this review. Retrieved citations were screened, and the data were extracted based on strict inclusion and exclusion criteria. Inclusion criteria include the article being full text, published from the year 2016 until 2020 and provided via open access resource or subscribed to by the institution. Quality assessment was done using Mixed Methods Appraisal Tools (MMAT) version 2018 to assess the methodological quality of the included studies. Given the heterogeneity of the included studies, a descriptive synthesis of the included studies was undertaken.
RESULTS: Out of 425 articles identified, 22 quantitative articles and one qualitative article were included in the final review. Both the risk and protective factors obtained were categorized into three main domains: individual, family, and community factors. The individual risk factors identified were traits of high impulsivity; rebelliousness; emotional regulation impairment, low religious, pain catastrophic, homework completeness, total screen time and alexithymia; the experience of maltreatment or a negative upbringing; having psychiatric disorders such as conduct problems and major depressive disorder; previous e-cigarette exposure; behavioral addiction; low-perceived risk; high-perceived drug accessibility; and high-attitude to use synthetic drugs. The familial risk factors were prenatal maternal smoking; poor maternal psychological control; low parental education; negligence; poor supervision; uncontrolled pocket money; and the presence of substance-using family members. One community risk factor reported was having peers who abuse drugs. The protective factors determined were individual traits of optimism; a high level of mindfulness; having social phobia; having strong beliefs against substance abuse; the desire to maintain one's health; high paternal awareness of drug abuse; school connectedness; structured activity and having strong religious beliefs.
CONCLUSION: The outcomes of this review suggest a complex interaction between a multitude of factors influencing adolescent drug abuse. Therefore, successful adolescent drug abuse prevention programs will require extensive work at all levels of domains.
Fulltext Hospital indoor air quality and its relationships with building design, building operation, and occupant-related factors: A mini-review

Ibrahim F, Samsudin EZ, Ishak AR, Sathasivam J

Front Public Health, 2022;10:1067764.
PMID: 36424957 DOI: 10.3389/fpubh.2022.1067764

Indoor air quality (IAQ) has recently gained substantial traction as the airborne transmission of infectious respiratory disease becomes an increasing public health concern. Hospital indoor environments are complex ecosystems and strategies to improve hospital IAQ require greater appreciation of its potentially modifiable determinants, evidence of which are currently limited. This mini-review updates and integrates findings of previous literature to outline the current scientific evidence on the relationship between hospital IAQ and building design, building operation, and occupant-related factors. Emerging evidence has linked aspects of building design (dimensional, ventilation, and building envelope designs, construction and finishing materials, furnishing), building operation (ventilation operation and maintenance, hygiene maintenance, access control for hospital users), and occupants' characteristics (occupant activities, medical activities, adaptive behavior) to hospital IAQ. Despite the growing pool of IAQ literature, some important areas within hospitals (outpatient departments) and several key IAQ elements (dimensional aspects, room configurations, building materials, ventilation practices, adaptive behavior) remain understudied. Ventilation for hospitals continues to be challenging, as elevated levels of carbon monoxide, bioaerosols, and chemical compounds persist in indoor air despite having mechanical ventilation systems in place. To curb this public health issue, policy makers should champion implementing hospital IAQ surveillance system for all areas of the hospital building, applying interdisciplinary knowledge during the hospital design, construction and operation phase, and training of hospital staff with regards to operation, maintenance, and building control manipulation. Multipronged strategies targeting these important determinants are believed to be a viable strategy for the future control and improvement of hospital IAQ.
Effects of Muslims praying (Salat) on EEG gamma activity

Doufesh H, Ibrahim F, Safari M

Complement Ther Clin Pract, 2016 Aug;24:6-10.
PMID: 27502795 DOI: 10.1016/j.ctcp.2016.04.004

This study investigates the difference of mean gamma EEG power between actual and mimic Salat practices in twenty healthy Muslim subjects. In the actual Salat practice, the participants were asked to recite and performing the physical steps in all four stages of Salat; whereas in the mimic Salat practice, they were instructed to perform only the physical steps without recitation. The gamma power during actual Salat was statistically higher than during mimic Salat in the frontal and parietal regions in all stages. In the actual Salat practice, the left hemisphere exhibited significantly higher mean gamma power in all cerebral regions and all stages, except the central-parietal region in the sitting position, and the frontal area in the bowing position. Increased gamma power during Salat, possibly related to an increase in cognitive and attentional processing, supports the concept of Salat as a focus attention meditation.
Fulltext Student satisfaction and academic efficacy during online learning with the mediating effect of student engagement: A multi-country study

Sharif Nia H, Marôco J, She L, Khoshnavay Fomani F, Rahmatpour P, Stepanovic Ilic I, et al.

PLoS One, 2023;18(10):e0285315.
PMID: 37792853 DOI: 10.1371/journal.pone.0285315

The COVID-19 pandemic caused unprecedented changes to educational institutions, forcing their closure and a subsequent shift to online education to cater to student learning requirements. However, successful online learning depends on several factors and may also vary between countries. As such, this cross-sectional study sought to investigate how engagement of university students, a major driver of online learning, was influenced by course content, online interaction, student acceptance, and satisfaction with online learning, as well as self-efficacy across nine countries (China, India, Iran, Italy, Malaysia, Portugal, Serbia, Turkey, and the United Arab Emirates) during the COVID-19 pandemic. Using a questionnaire-based approach, data collected from 6,489 university students showed that student engagement was strongly linked to perception of the quality of the course content and online interactions (p < .001). The current study also indicated that online interactions are a major determinant of academic efficacy but only if mediated by engagement within the online learning context. A negative correlation between student engagement and satisfaction with online learning was found, demonstrating the importance of students being engaged behaviorally, emotionally, and cognitively to feel satisfied with learning. Academic efficacy and student satisfaction were explained by course content, online interaction, and online learning acceptance, being mediated by student engagement. Student satisfaction and, to a lesser degree academic efficacy, were also associated with online learning acceptance. Overall, the structural equation model was a good fit for the data collected from all nine countries (CFI = .947, TLI = .943; RMSEA = .068; SRMR = .048), despite differences in the percentage variations explained by each factor (no invariance), likely due to differences in levels of technology use, learning management systems, and the preparedness of teachers to migrate to full online instruction. Despite limitations, the results of this study highlight the most important factors affecting online learning, providing insight into potential approaches for improving student experiences in online learning environments.
Fulltext Muslim prayer movements as an alternative therapy in the treatment of erectile dysfunction: a preliminary study

Ibrahim F, Sian TC, Shanggar K, Razack AH

J Phys Ther Sci, 2013 Sep;25(9):1087-91.
PMID: 24259921 DOI: 10.1589/jpts.25.1087

[Purpose] Our objective was to assess the effect of salat and mimicking salat movements and postures on subjects with erectile dysfunction. [Methods] Ten volunteers were recruited in this study. Subjects who were Muslims (Group I) were asked to perform their daily salat and a new intervention of an additional 12 movement cycles of salat for three sessions a week. Non-Muslim subjects (Group II) were taught to mimic salat movements, and were asked to perform a total of 12 movement cycles without reading the recitation for three sessions a week. An International Index for Erectile Function 5 (IIEF-5) questionnaire was given to the subjects before and after the intervention of performing salat or mimicking salat movements and postures. A nocturnal electrobioimpedance volume assessment (NEVA) device was used to measure the nocturnal penile tumescence (NPT) parameters over two consecutive nights. A nonparametric test was conducted to find the significant NPT parameters. [Results] The results showed that all measured parameters improved significantly, with the largest change observed in the maximum percent volumetric change over the baseline (from 138 to 222%). [Conclusion] This preliminary study suggests that the alternative approach of salat and mimicking salat movements and postures, may have beneficial effects for ED patients.
Socioeconomic Predictors of Adherence Behavior Among HIV-Positive Patients Receiving Antiretroviral Therapy in Selangor, Malaysia

Abdulrahman SA, Rampal L, Othman N, Ibrahim F, Kadir Shahar H, Radhakrishnan AP

Asia Pac J Public Health, 2017 May;29(4):304-314.
PMID: 28397533 DOI: 10.1177/1010539517700471

Medication adherence remains a critical link between the prescribed ART regimen and treatment outcome. Several factors may influence adherence behavior. This cross-sectional study aimed to highlight socioeconomic predictors of adherence behavior among a cohort of 242 adult Malaysian patients receiving antiretroviral therapy in Hospital Sungai Buloh, Malaysia, where they were enrolled in a parent study (single-blinded randomized controlled trial) between January and December 2014. Statistical analysis of secondary data on adherence behavior and sociodemographic characteristics of the patients revealed mean age of 33.4 years and ranged from 18 to 64 years; 88.8% were males. A total of 224 (93%) patients who completed 6 months' adherence assessment were included in the model. Of these, 135 (60.3%) achieved optimal adherence. Multivariate binary logistic regression analysis revealed that patient's income and ethnicity were significant predictors of adherence behavior. This may be valuable for targeted programmatic interventions to further enhance successful treatment outcomes among the target population.
Fulltext Sociodemographic profile and predictors of outpatient clinic attendance among HIV-positive patients initiating antiretroviral therapy in Selangor, Malaysia

Abdulrahman SA, Rampal L, Othman N, Ibrahim F, Hayati KS, Radhakrishnan AP

Patient Prefer Adherence, 2017;11:1273-1284.
PMID: 28794617 DOI: 10.2147/PPA.S141609

BACKGROUND: Inconsistent literature evidence suggests that sociodemographic, economic, and system- and patient-related factors are associated with clinic attendance among the HIV-positive population receiving antiretroviral therapy (ART) around the world. We examined the factors that predict outpatient clinic attendance among a cohort of HIV-positive patients initiating ART in Selangor, Malaysia.

PATIENTS AND METHODS: This cross-sectional study analyzed secondary data on outpatient clinic attendance and sociodemographic, economic, psychosocial, and patient-related factors among 242 adult Malaysian patients initiating ART in Selangor, Malaysia. Study cohort was enrolled in a parent randomized controlled trial (RCT) in Hospital Sungai Buloh Malaysia between January and December 2014, during which peer counseling, medication, and clinic appointment reminders were provided to the intervention group through short message service (SMS) and telephone calls for 24 consecutive weeks. Data on outpatient clinic attendance were extracted from the hospital electronic medical records system, while other patient-level data were extracted from pre-validated Adult AIDS Clinical Trial Group (AACTG) adherence questionnaires in which primary data were collected. Outpatient clinic attendance was categorized into binary outcome - regular attendee and defaulter categories - based on the number of missed scheduled outpatient clinic appointments within a 6-month period. Multivariate regression models were fitted to examine predictors of outpatient clinic attendance using SPSS version 22 and R software.

RESULTS: A total of 224 (93%) patients who completed 6-month assessment were included in the model. Out of those, 42 (18.7%) defaulted scheduled clinic attendance at least once. Missed appointments were significantly more prevalent among females (n=10, 37.0%), rural residents (n=10, 38.5%), and bisexual respondents (n=8, 47.1%). Multivariate binary logistic regression analysis showed that Indian ethnicity (adjusted odds ratio [AOR] =0.235; 95% CI [0.063-0.869]; P=0.030) and heterosexual orientation (AOR =4.199; 95% CI [1.040-16.957]; P=0.044) were significant predictors of outpatient clinic attendance among HIV-positive patients receiving ART in Malaysia.

CONCLUSION: Ethnicity and sexual orientation of Malaysian patients may play a significant role in their level of adherence to scheduled clinic appointments. These factors should be considered during collaborative adherence strategy planning at ART initiation.

Study site: Outpatient clinic, Hospital Sungai Buloh Malaysia
Testing comparison models of DASS-12 and its reliability among adolescents in Malaysia

Osman ZJ, Mukhtar F, Hashim HA, Abdul Latiff L, Mohd Sidik S, Awang H, et al.

Compr Psychiatry, 2014 Oct;55(7):1720-5.
PMID: 24952938 DOI: 10.1016/j.comppsych.2014.04.011

OBJECTIVE: The 21-item Depression, Anxiety and Stress Scale (DASS-21) is frequently used in non-clinical research to measure mental health factors among adults. However, previous studies have concluded that the 21 items are not stable for utilization among the adolescent population. Thus, the aims of this study are to examine the structure of the factors and to report on the reliability of the refined version of the DASS that consists of 12 items.
METHOD: A total of 2850 students (aged 13 to 17 years old) from three major ethnic in Malaysia completed the DASS-21. The study was conducted at 10 randomly selected secondary schools in the northern state of Peninsular Malaysia. The study population comprised secondary school students (Forms 1, 2 and 4) from the selected schools.
RESULTS: Based on the results of the EFA stage, 12 items were included in a final CFA to test the fit of the model. Using maximum likelihood procedures to estimate the model, the selected fit indices indicated a close model fit (χ(2)=132.94, df=57, p=.000; CFI=.96; RMR=.02; RMSEA=.04). Moreover, significant loadings of all the unstandardized regression weights implied an acceptable convergent validity. Besides the convergent validity of the item, a discriminant validity of the subscales was also evident from the moderate latent factor inter-correlations, which ranged from .62 to .75. The subscale reliability was further estimated using Cronbach's alpha and the adequate reliability of the subscales was obtained (Total=76; Depression=.68; Anxiety=.53; Stress=.52).
CONCLUSION: The new version of the 12-item DASS for adolescents in Malaysia (DASS-12) is reliable and has a stable factor structure, and thus it is a useful instrument for distinguishing between depression, anxiety and stress.
Fulltext Mobile phone reminders and peer counseling improve adherence and treatment outcomes of patients on ART in Malaysia: A randomized clinical trial

Abdulrahman SA, Rampal L, Ibrahim F, Radhakrishnan AP, Kadir Shahar H, Othman N

PLoS One, 2017;12(5):e0177698.
PMID: 28520768 DOI: 10.1371/journal.pone.0177698

BACKGROUND: Adherence to treatment remains the cornerstone of long term viral suppression and successful treatment outcomes among patients receiving Antiretroviral Therapy (ART).
OBJECTIVE(S): Evaluate the effectiveness of mobile phone reminders and peer counseling in improving adherence and treatment outcomes among HIV positive patients on ART in Malaysia.
METHODS: A single-blind, parallel group RCT conducted in Hospital Sungai Buloh, Malaysia in which 242 adult Malaysian patients were randomized to intervention or control groups. Intervention consisted of a reminder module delivered through SMS and telephone call reminders by trained research assistants for 24 consecutive weeks (starting from date of ART initiation), in addition to adherence counseling at every clinic visit. The length of intended follow up for each patient was 6 months. Data on adherence behavior of patients was collected using specialized, pre-validated Adult AIDS Clinical Trial Group (AACTG) adherence questionnaires. Data on weight, clinical symptoms, CD4 count and viral load tests were also collected. Data was analyzed using SPSS version 22 and R software. Repeated measures ANOVA, Friedman's ANOVA and Multivariate regression models were used to evaluate efficacy of the intervention.
RESULTS: The response rate after 6 months follow up was 93%. There were no significant differences at baseline in gender, employment status, income distribution and residential location of respondents between the intervention and control group. After 6 months follow up, the mean adherence was significantly higher in the intervention group (95.7; 95% CI: 94.39-96.97) as compared to the control group (87.5; 95% CI: 86.14-88.81). The proportion of respondents who had Good (>95%) adherence was significantly higher in the intervention group (92.2%) compared to the control group (54.6%). A significantly lower frequency in missed appointments (14.0% vs 35.5%) (p = 0.001), lower viral load (p = 0.001), higher rise in CD4 count (p = 0.017), lower incidence of tuberculosis (p = 0.001) and OIs (p = 0.001) at 6 months follow up, was observed among patients in the intervention group.
CONCLUSION: Mobile phone reminders (SMS and telephone call reminders) and peer counseling are effective in improving adherence and treatment outcomes among HIV positive patients on ART in Malaysia. These findings may be of potential benefit for collaborative adherence planning between patients and health care providers at ART commencement.
Fulltext A quantitative approach to measure women's sexual function using electromyography: a preliminary study of the Kegel exercise

Mohktar MS, Ibrahim F, Mohd Rozi NF, Mohd Yusof J, Ahmad SA, Su Yen K, et al.

Med Sci Monit, 2013 Dec 13;19:1159-66.
PMID: 24335927 DOI: 10.12659/MSM.889628

BACKGROUND: Currently, the reference standard used to clinically assess sexual function among women is a qualitative questionnaire. Hence, a generalised and quantitative measurement tool needs to be available as an alternative. This study investigated whether an electromyography (EMG) measurement technique could be used to help quantify women's sexual function.
MATERIAL AND METHODS: A preliminary intervention study was conducted on 12 female subjects, who were randomised into a control (n=6) and an intervention (n=6) group. Intervention involved a set regimen of pelvic floor muscle exercises (Kegel) and the control group did not have any treatment. All subjects were asked to answer a validated, self-rated Pelvic Organ Prolapse/Urinary Incontinence Sexual Function Questionnaire (PISQ). EMG measurements of the pelvic floor muscles (PFM) and the abdominal muscles were taken from all women at recruitment and 8 weeks after study commencement.
RESULTS: After 8 weeks, most of the subjects in the control group did not display any noted positive difference in either PISQ score (4/6) or in their muscle strength (4/6). However, a noted progressive difference were observed in subjects who were placed in the Kegel group; PISQ score (5/6) and muscles strength (4/6).
CONCLUSIONS: The noted difference in the Kegel group subjects was that if progress is observed in the sexual function, improvement is also observed in the strength of at least 2 types of muscles (either abdominal or PFM muscles). Thus, EMG measurement is a potential technique to quantify the changes in female sexual function. Further work will be conducted to validate this assumption.
Intelligent classification of electrocardiogram (ECG) signal using extended Kalman Filter (EKF) based neuro fuzzy system

Meau YP, Ibrahim F, Narainasamy SA, Omar R

Comput Methods Programs Biomed, 2006 May;82(2):157-68.
PMID: 16638620

This study presents the development of a hybrid system consisting of an ensemble of Extended Kalman Filter (EKF) based Multi Layer Perceptron Network (MLPN) and a one-pass learning Fuzzy Inference System using Look-up Table Scheme for the recognition of electrocardiogram (ECG) signals. This system can distinguish various types of abnormal ECG signals such as Ventricular Premature Cycle (VPC), T wave inversion (TINV), ST segment depression (STDP), and Supraventricular Tachycardia (SVT) from normal sinus rhythm (NSR) ECG signal.
Fulltext The application of biomedical engineering techniques to the diagnosis and management of tropical diseases: a review

Ibrahim F, Thio TH, Faisal T, Neuman M

Sensors (Basel), 2015 Mar 23;15(3):6947-95.
PMID: 25806872 DOI: 10.3390/s150306947

This paper reviews a number of biomedical engineering approaches to help aid in the detection and treatment of tropical diseases such as dengue, malaria, cholera, schistosomiasis, lymphatic filariasis, ebola, leprosy, leishmaniasis, and American trypanosomiasis (Chagas). Many different forms of non-invasive approaches such as ultrasound, echocardiography and electrocardiography, bioelectrical impedance, optical detection, simplified and rapid serological tests such as lab-on-chip and micro-/nano-fluidic platforms and medical support systems such as artificial intelligence clinical support systems are discussed. The paper also reviewed the novel clinical diagnosis and management systems using artificial intelligence and bioelectrical impedance techniques for dengue clinical applications.
Elastic reversible valves on centrifugal microfluidic platforms

Aeinehvand MM, Weber L, Jiménez M, Palermo A, Bauer M, Loeffler FF, et al.

Lab Chip, 2019 Feb 20.
PMID: 30785443 DOI: 10.1039/c8lc00849c

Reversible valves on centrifugal microfluidic platforms facilitate the automation of bioanalytical assays, especially of those requiring a series of steps (such as incubation) in a single reaction chamber. In this study, we present fixed elastic reversible (FER) valves and tunable elastic reversible (TER) valves that are easy to fabricate, implement and control. In the FER valve the compression of an elastic barrier/patch against a microchamber's outlet prevents the release of liquid. The valve sealing pressure was determined by adjusting the engraving depth of the valve-seat at which the elastic patch was located, this allows to set the sealing pressure during disc fabrication. In the TER valve, the patch compression value and sealing pressure is controlled by the penetration depth of a plastic screw into the valve-seat. The ER valves prevent liquid flow until the centrifugal force overcomes their sealing pressure. Moreover, at a constant spin speed, turning the screw of a TER valve reduces its sealing pressure and opens the valve. Therefore, the TER valve allows for controlling of the liquid transfer volume at various spin speeds. The FER and TER valves' behavior is mathematically described and equations for the prediction of their operation under centrifugal forces are provided. As a point-of-care (POC) application of ER valves, we have developed a microfluidic disc with a series of TER valves and peptide microarrays for automated multiplexed detection of five different proteins from a single serum sample.
Fine root dynamics across pantropical rainforest ecosystems

Huaraca Huasco W, Riutta T, Girardin CAJ, Hancco Pacha F, Puma Vilca BL, Moore S, et al.

Glob Chang Biol, 2021 08;27(15):3657-3680.
PMID: 33982340 DOI: 10.1111/gcb.15677

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old-growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi-deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water-stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting that root productivity is a particularly strong driver of NPP allocation in tropical mountain regions.
Biosensing enhancement of dengue virus using microballoon mixers on centrifugal microfluidic platforms

Aeinehvand MM, Ibrahim F, Harun SW, Djordjevic I, Hosseini S, Rothan HA, et al.

Biosens Bioelectron, 2015 May 15;67:424-30.
PMID: 25220800 DOI: 10.1016/j.bios.2014.08.076

Dengue is the current leading cause of death among children in several Latin American and Asian countries. Due to poverty in areas where the disease is prevalent and the high cost of conventional diagnostic systems, low cost devices are needed to reduce the burden caused by dengue infection. Centrifugal microfluidic platforms are an alternative solution to reduce costs and increase the availability of a rapid diagnostic system. The rate of chemical reactions in such devices often depends on the efficiency of the mixing techniques employed in their microfluidic networks. This paper introduces a micromixer that operates by the expansion and contraction of a microballoon to produce a consistent periodical 3D reciprocating flow. We established that microballoons reduced mixing time of 12 μl liquids from 170 min, for diffusional mixing, to less than 23 s. We have also tested the effect of the microballoon mixers on the detection of the dengue virus. The results indicate that employing a microballoon mixer enhances the detection sensitivity of the dengue virus by nearly one order of magnitude compared to the conventional ELISA method.
Fulltext The effect of contact angles and capillary dimensions on the burst frequency of super hydrophilic and hydrophilic centrifugal microfluidic platforms, a CFD study

Kazemzadeh A, Ganesan P, Ibrahim F, He S, Madou MJ

PLoS One, 2013;8(9):e73002.
PMID: 24069169 DOI: 10.1371/journal.pone.0073002

This paper employs the volume of fluid (VOF) method to numerically investigate the effect of the width, height, and contact angles on burst frequencies of super hydrophilic and hydrophilic capillary valves in centrifugal microfluidic systems. Existing experimental results in the literature have been used to validate the implementation of the numerical method. The performance of capillary valves in the rectangular and the circular microfluidic structures on super hydrophilic centrifugal microfluidic platforms is studied. The numerical results are also compared with the existing theoretical models and the differences are discussed. Our experimental and computed results show a minimum burst frequency occurring at square capillaries and this result is useful for designing and developing more sophisticated networks of capillary valves. It also predicts that in super hydrophilic microfluidics, the fluid leaks consistently from the capillary valve at low pressures which can disrupt the biomedical procedures in centrifugal microfluidic platforms.
Fulltext Microplasma direct writing for site-selective surface functionalization of carbon microelectrodes

Thiha A, Ibrahim F, Muniandy S, Madou MJ

Microsyst Nanoeng, 2019;5:62.
PMID: 31754454 DOI: 10.1038/s41378-019-0103-0

Carbon micro- and nanoelectrodes fabricated by carbon microelectromechanical systems (carbon MEMS) are increasingly used in various biosensors and supercapacitor applications. Surface modification of as-produced carbon electrodes with oxygen functional groups is sometimes necessary for biofunctionalization or to improve electrochemical properties. However, conventional surface treatment methods have a limited ability for selective targeting of parts of a surface area for surface modification without using complex photoresist masks. Here, we report microplasma direct writing as a simple, low-cost, and low-power technique for site-selective plasma patterning of carbon MEMS electrodes with oxygen functionalities. In microplasma direct writing, a high-voltage source generates a microplasma discharge between a microelectrode tip and a target surface held at atmospheric pressure. In our setup, water vapor acts as an ionic precursor for the carboxylation and hydroxylation of carbon surface atoms. Plasma direct writing increases the oxygen content of an SU-8-derived pyrolytic carbon surface from ~3 to 27% while reducing the carbon-to-oxygen ratio from 35 to 2.75. Specifically, a microplasma treatment increases the number of carbonyl, carboxylic, and hydroxyl functional groups with the largest increase observed for carboxylic functionalities. Furthermore, water microplasma direct writing improves the hydrophilicity and the electrochemical performance of carbon electrodes with a contact-angle change from ~90° to ~20°, a reduction in the anodic peak to cathodic peak separation from 0.5 V to 0.17 V, and a 5-fold increase in specific capacitance from 8.82 mF∙cm-2 to 46.64 mF∙cm-2. The plasma direct-writing technology provides an efficient and easy-to-implement method for the selective surface functionalization of carbon MEMS electrodes for electrochemical and biosensor applications.

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