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Displaying publications 41 - 57 of 57 in total

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Paper-based sample-to-answer molecular diagnostic platform for point-of-care diagnostics

Choi JR, Tang R, Wang S, Wan Abas WA, Pingguan-Murphy B, Xu F

Biosens Bioelectron, 2015 Dec 15;74:427-39.
PMID: 26164488 DOI: 10.1016/j.bios.2015.06.065

Nucleic acid testing (NAT), as a molecular diagnostic technique, including nucleic acid extraction, amplification and detection, plays a fundamental role in medical diagnosis for timely medical treatment. However, current NAT technologies require relatively high-end instrumentation, skilled personnel, and are time-consuming. These drawbacks mean conventional NAT becomes impractical in many resource-limited disease-endemic settings, leading to an urgent need to develop a fast and portable NAT diagnostic tool. Paper-based devices are typically robust, cost-effective and user-friendly, holding a great potential for NAT at the point of care. In view of the escalating demand for the low cost diagnostic devices, we highlight the beneficial use of paper as a platform for NAT, the current state of its development, and the existing challenges preventing its widespread use. We suggest a strategy involving integrating all three steps of NAT into one single paper-based sample-to-answer diagnostic device for rapid medical diagnostics in the near future.
Cryopreservation of Human Mesenchymal Stem Cells for Clinical Applications: Current Methods and Challenges

Yong KW, Wan Safwani WK, Xu F, Wan Abas WA, Choi JR, Pingguan-Murphy B

Biopreserv Biobank, 2015 Aug;13(4):231-9.
PMID: 26280501 DOI: 10.1089/bio.2014.0104

Mesenchymal stem cells (MSCs) hold many advantages over embryonic stem cells (ESCs) and other somatic cells in clinical applications. MSCs are multipotent cells with strong immunosuppressive properties. They can be harvested from various locations in the human body (e.g., bone marrow and adipose tissues). Cryopreservation represents an efficient method for the preservation and pooling of MSCs, to obtain the cell counts required for clinical applications, such as cell-based therapies and regenerative medicine. Upon cryopreservation, it is important to preserve MSCs functional properties including immunomodulatory properties and multilineage differentiation ability. Further, a biosafety evaluation of cryopreserved MSCs is essential prior to their clinical applications. However, the existing cryopreservation methods for MSCs are associated with notable limitations, leading to a need for new or improved methods to be established for a more efficient application of cryopreserved MSCs in stem cell-based therapies. We review the important parameters for cryopreservation of MSCs and the existing cryopreservation methods for MSCs. Further, we also discuss the challenges to be addressed in order to preserve MSCs effectively for clinical applications.
Re: Re: "Quantitative and Qualitative Comparison of a New Prosthetic Suspension System with Two Existing Suspension Systems for Lower Limb Amputees"

Eshraghi A, Osman NA, Karimi MT, Gholizadeh H, Ali S, Wan Abas WA

Am J Phys Med Rehabil, 2015 Jul;94(7):e60.
PMID: 25888670 DOI: 10.1097/PHM.0000000000000304
Investigation to predict patellar tendon reflex using motion analysis technique

Tham LK, Osman NA, Lim KS, Pingguan-Murphy B, Abas WA, Zain NM

Med Eng Phys, 2011 May;33(4):407-10.
PMID: 21146440 DOI: 10.1016/j.medengphy.2010.11.002

The investigation of patellar tendon reflex involves development of a reflex hammer holder, kinematic data collection and analysis of patellar reflex responses using motion analysis techniques. The main aim of this research is to explore alternative means of assessing reflexes as a part of routine clinical diagnosis. The motion analysis system was applied to provide quantitative data which is a more objective measure of the patellar tendon reflex. Kinematic data was collected from 28 males and 22 females whilst subjected to a knee jerk test. Further analysis of kinematic data was performed to predict relationships which might affect the patellar tendon reflex. All subjects were seated on a high stool with their legs hanging freely within the capture volume of the motion analysis system. Knee jerk tests were applied to all subjects, on both sides of the leg, by eliciting hypo, hyper, and normal reflexes. An additional reinforcement technique called the Jendrassik manoeuvre was also performed under the same conditions to elicit a normal patellar tendon reflex. The comparison of reflex response between genders showed that female subjects generally had a greater response compared to males. However, the difference in reflex response between the left leg and the right leg was not significant. Tapping strength to elicit a hyper-reflex produced greater knee-jerk compared to the normal clinical tapping strength. All results were in agreement with clinical findings and results found by some early researchers.
In vitro comparative study of white and dark polycaprolactone trifumarate in situ cross-linkable scaffolds seeded with rat bone marrow stromal cells

Muhammad KB, Abas WA, Kim KH, Pingguan-Murphy B, Zain NM, Akram H

Clinics (Sao Paulo), 2012;67(6):629-38.
PMID: 22760903

OBJECTIVE: Dark poly(caprolactone) trifumarate is a successful candidate for use as a bone tissue engineering scaffold. Recently, a white polymeric scaffold was developed that shows a shorter synthesis time and is more convenient for tissue-staining work. This is an in vitro comparative study of both the white and dark scaffolds.
METHODS: Both white and dark poly(caprolactone) trifumarate macromers were characterized via Fourier transform infrared spectroscopy before being chemically cross-linked and molded into disc-shaped scaffolds. Biodegradability was assessed by percentage weight loss on days 7, 14, 28, 42 and 56 (n = 5) after immersion in 10% serum-supplemented medium or distilled water. Static cell seeding was employed in which isolated and characterized rat bone marrow stromal cells were seeded directly onto the scaffold surface. Seeded scaffolds were subjected to a series of biochemical assays and scanning electron microscopy at specified time intervals for up to 28 days of incubation.
RESULTS: The degradation of the white scaffold was significantly lower compared with the dark scaffold but was within the acceptable time range for bone-healing processes. The deoxyribonucleic acid and collagen contents increased up to day 28 with no significant difference between the two scaffolds, but the glycosaminoglycan content was slightly higher in the white scaffold throughout 14 days of incubation. Scanning electron microscopy at day 1 [corrected] revealed cellular growth and attachment.
CONCLUSIONS: There was no cell growth advantage between the two forms, but the white scaffold had a slower biodegradability rate, suggesting that the newly synthesized poly(caprolactone) trifumarate is more suitable for use as a bone tissue engineering scaffold.
Fulltext Computational fluid dynamics modelling of microfluidic channel for dielectrophoretic BioMEMS application

Low WS, Kadri NA, Abas WA

ScientificWorldJournal, 2014;2014:961301.
PMID: 25136701 DOI: 10.1155/2014/961301

We propose a strategy for optimizing distribution of flow in a typical benchtop microfluidic chamber for dielectrophoretic application. It is aimed at encouraging uniform flow velocity along the whole analysis chamber in order to ensure DEP force is evenly applied to biological particle. Via the study, we have come up with a constructive strategy in improving the design of microfluidic channel which will greatly facilitate the use of DEP system in laboratory and primarily focus on the relationship between architecture and cell distribution, by resorting to the tubular structure of blood vessels. The design was validated by hydrodynamic flow simulation using COMSOL Multiphysics v4.2a software. Simulations show that the presence of 2-level bifurcation has developed portioning of volumetric flow which produced uniform flow across the channel. However, further bifurcation will reduce the volumetric flow rate, thus causing undesirable deposition of cell suspension around the chamber. Finally, an improvement of microfluidic design with rounded corner is proposed to encourage a uniform cell adhesion within the channel.
The effect of Dermo and Seal-In X5 prosthetic liners on pressure distributions and reported satisfaction during ramp ambulation in persons with transtibial limb loss

Ali S, Osman NA, Razak A, Hussain S, Wan Abas WA

Eur J Phys Rehabil Med, 2015 Feb;51(1):31-7.
PMID: 24963603

Lower limb amputee's are greatly affected in dealing with the environmental barriers such as ramps and stairs and reported high interface pressure between the residual limb and socket/liner. Interface pressure between the residual limb and socket/liner can affect the satisfaction and use of the prosthesis. Until now, little attention has been paid to interface pressure between socket and stump during ramp negotiation and its effect on amputee's satisfaction.
Fulltext The effects of prosthetic foot type and visual alteration on postural steadiness in below-knee amputees

Arifin N, Abu Osman NA, Ali S, Wan Abas WA

Biomed Eng Online, 2014;13(1):23.
PMID: 24597518 DOI: 10.1186/1475-925X-13-23

Achieving independent upright posture has known to be one of the main goals in rehabilitation following lower limb amputation. The purpose of this study was to compare postural steadiness of below knee amputees with visual alterations while wearing three different prosthetic feet.
Fulltext Balance control in lower extremity amputees during quiet standing: a systematic review

Ku PX, Abu Osman NA, Wan Abas WA

Gait Posture, 2014 Feb;39(2):672-82.
PMID: 24331296 DOI: 10.1016/j.gaitpost.2013.07.006

Postural control has been widely evaluated for the normal population and different groups over the past 20 years. Numerous studies have investigated postural control in quiet standing posture among amputees. However, a comprehensive analysis is lacking on the possible contributing factors to balance. The present systematic review highlights the current findings on variables that contribute to balance instability for lower extremity amputees. The search strategy was performed on PubMed, Web of Science, Medline, Scopus, and CINAHL and then followed by additional manual searching via reference lists in the reviewed articles. The quality of the articles was evaluated using a methodological quality assessment tool. This review included and evaluated a total of 23 full-text articles. Despite the inconsistencies in the methodological design of the studies, all articles scored above the acceptable level in terms of quality. A majority of the studies revealed that lower extremity amputees have increased postural sway in the standing posture. Asymmetry in body weight, which is mainly distributed in the non-amputated leg, was described. Aside from the centre of pressure in postural control, sensory inputs may be a related topic for investigation in view of evidence on their contribution, particularly visual input. Other balance-related factors, such as stump length and patients' confidence level, were also neglected. Further research requires examination on the potential factors that affect postural control as the information of standing postural is still limited.
Intrarater test-retest reliability of static and dynamic stability indexes measurement using the Biodex Stability System during unilateral stance

Arifin N, Abu Osman NA, Wan Abas WA

J Appl Biomech, 2014 Apr;30(2):300-4.
PMID: 23878204 DOI: 10.1123/jab.2013-0130

The measurements of postural balance often involve measurement error, which affects the analysis and interpretation of the outcomes. In most of the existing clinical rehabilitation research, the ability to produce reliable measures is a prerequisite for an accurate assessment of an intervention after a period of time. Although clinical balance assessment has been performed in previous study, none has determined the intrarater test-retest reliability of static and dynamic stability indexes during dominant single stance. In this study, one rater examined 20 healthy university students (female=12, male=8) in two sessions separated by 7 day intervals. Three stability indexes--the overall stability index (OSI), anterior/posterior stability index (APSI), and medial/ lateral stability index (MLSI) in static and dynamic conditions--were measured during single dominant stance. Intraclass correlation coefficient (ICC), standard error measurement (SEM) and 95% confidence interval (95% CI) were calculated. Test-retest ICCs for OSI, APSI, and MLSI were 0.85, 0.78, and 0.84 during static condition and were 0.77, 0.77, and 0.65 during dynamic condition, respectively. We concluded that the postural stability assessment using Biodex stability system demonstrates good-to-excellent test-retest reliability over a 1 week time interval.
Biomechanical evaluation of the relationship between postural control and body mass index

Ku PX, Abu Osman NA, Yusof A, Wan Abas WA

J Biomech, 2012 Jun 1;45(9):1638-42.
PMID: 22507349 DOI: 10.1016/j.jbiomech.2012.03.029

Postural stability is crucial in maintaining body balance during quiet standing, locomotion, and any activities that require a high degree of balance performance, such as participating in sports and dancing. Research has shown that there is a relationship between stability and body mass. The aims of this study were to examine the impact that two variables had on static postural control: body mass index (BMI) and gender. Eighty healthy young adults (age=21.7±1.8 yr; height=1.65±0.09 m; mass=67.5±19.0 kg) participated in the study and the static postural control was assessed using the Biodex Balance System, with a 20 Hz sampling rate in the bipedic stance (BLS) and unipedic stance (ULS) for 30s. Five test evaluations were performed for each balance test. Postural control was found to be negatively correlated with increased adiposity, as the obese BMI group performed significantly poorer than the underweight, normal weight and overweight groups during BLS and ULS tests. The underweight, normal weight and overweight groups exhibited greater anterior-posterior stability in postural control during quiet stance. In addition, female displayed a trend of having a greater postural sway than male young adults, although it was evidenced in only some BMI groups. This study revealed that BMI do have an impact on postural control during both BLS and ULS. As such, BMI and gender-specific effects should be taken into consideration when selecting individuals for different types of sporting activities, especially those that require quiet standing.
Kinematic comparison of the wrist movements that are possible with a biomechatronics wrist prosthesis and a body-powered prosthesis: a preliminary study

Abd Razak NA, Abu Osman NA, Wan Abas WA

Disabil Rehabil Assist Technol, 2013 May;8(3):255-60.
PMID: 22830946 DOI: 10.3109/17483107.2012.704654

This study examined the kinematic differences between a body-powered prosthesis and a biomechatronics prosthesis as a transradial amputee performed activities that involve flexion/extension and supination/pronation of the wrist.
Fulltext Modeling of hemoglobin in dengue fever and dengue hemorrhagic fever using bioelectrical impedance

Ibrahim F, Ismail NA, Taib MN, Wan Abas WA

Physiol Meas, 2004 Jun;25(3):607-15.
PMID: 15253113 DOI: 10.1088/0967-3334/25/3/002

This paper describes a model for predicting hemoglobin (Hb) by using bioelectrical impedance analysis (BIA) in dengue patients in the Hospital Universiti Kebangsaan Malaysia (HUKM). Bioelectrical impedance measurements were conducted on 83 (47 males and 36 females) serologically confirmed dengue fever (DF) and dengue hemorrhagic fever (DHF) patients during their hospitalization. The predictive equation for Hb was derived using multivariate analysis. We investigated all the parameters in BIA, patients' symptom and demographic data. In this developed model, four predictors (reactance (XC), sex, weight and vomiting) were found to be the best predictive factors for modeling Hb in dengue patients. However, the model can only explain approximately 42% of the variation in Hb status, thus single frequency bio-impedance stand-alone technique is insufficient to monitor Hb for the DF and DHF patients. Further investigation using multi-frequency BIA is recommended in modeling Hb to achieve the most parsimonious model.
Fulltext Benchtop technologies for circulating tumor cells separation based on biophysical properties

Low WS, Wan Abas WA

Biomed Res Int, 2015;2015:239362.
PMID: 25977918 DOI: 10.1155/2015/239362

Circulating tumor cells (CTCs) are tumor cells that have detached from primary tumor site and are transported via the circulation system. The importance of CTCs as prognostic biomarker is leveraged when multiple studies found that patient with cutoff of 5 CTCs per 7.5 mL blood has poor survival rate. Despite its clinical relevance, the isolation and characterization of CTCs can be quite challenging due to their large morphological variability and the rare presence of CTCs within the blood. Numerous methods have been employed and discussed in the literature for CTCs separation. In this paper, we will focus on label free CTCs isolation methods, in which the biophysical and biomechanical properties of cells (e.g., size, deformability, and electricity) are exploited for CTCs detection. To assess the present state of various isolation methods, key performance metrics such as capture efficiency, cell viability, and throughput will be reported. Finally, we discuss the challenges and future perspectives of CTC isolation technologies.
Modelling the mechanical response of skin in vivo using the Bossinesq and the Michell stress functions

Wan Abas WA, Asseli MR

Biomed Mater Eng, 1994;4(7):463-71.
PMID: 7881330

Local strains acting across an area of skin loaded uniaxially in vivo are converted to stresses using the standard elastic formulae. The stress values are compared to those obtained using the classical Bossinesq and Michell stress functions. The results indicate that these functions are capable of describing the response of the skin, both in the low load and the high load regions.
Stress stabilisation behaviours in skin under small tensile loads in vitro

Wan Abas WA

Biomed Mater Eng, 1995;5(2):59-63.
PMID: 7655319

The response of human skin to "stress relaxation" tests at low loads in vitro was investigated. A number of behaviours, other than those already well established and documented, were observed. The significant behaviours are pure recovery and relaxation-recovery. Other behaviours observed are temporary stress recovery during the relaxation process, and momentary sudden non-linear drop in stress value followed by a second relaxation. The pure recovery and relaxation-recovery responses are repeatable. The latter represents the transitional response between the well-known behaviour of stress relaxation and the behaviour of stress recovery.
Biaxial tension test of human skin in vivo

Wan Abas WA

Biomed Mater Eng, 1994;4(7):473-86.
PMID: 7881331

The response of human skin to biaxial stretch tests in vivo was investigated and compared to the response to uniaxial tension. The results obtained illustrate the nonlinear, anisotropic, and viscoelastic (time-dependent) properties of skin under biaxial stretch. Preconditioning in the load-extension response was found not to be prominent. The results also suggest that the response of skin to a biaxial stretch in vivo is qualitatively similar to that in vitro. Values of the terminal stiffness and limit strain of skin under a biaxial stretch are found.

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