Kian Sek Tee

Biophysical characteristics of cells cultured on cholesteryl ester liquid crystals

This study aimed at examining the biophysical characteristics of human derived keratinocytes (HaCaT) cultured on cholesteryl ester liquid crystals (CELC). CELC was previously shown to improve sensitivity in sensing cell contractions. Characteristics of the cell integrin expressions and presence of extracellular matrix (ECM) proteins on the liquid crystals were interrogated using various immunocytochemical techniques. The investigation was followed by characterization of the chemical properties of the liquid crystals (LC) after immersion in cell culture media using Fourier transform infrared spectroscopy (FTIR). The surface morphology of cells adhered to the LC was studied using atomic force microscopy (AFM). Consistent with the expressions of the integrins α2, α3 and β1, extracellular matrix proteins (laminin, collagen type IV and fibronectin) were found secreted by the HaCaT onto CELC and these proteins were also secreted by cells cultured on the glass substrates. FTIR analysis of the LC revealed the existence of spectrum assigned to cholesterol and ester moieties that are essential compounds for the metabolizing activities of keratinocytes. The immunostainings indicated that cell adhesion on the LC is mediated by self-secreted ECM proteins. As revealed by the AFM imaging, the constraint in cell membrane spread on the LC leads to the increase in cell surface roughness and thickness of cell membrane. The biophysical expressions of cells on biocompatible CELC suggested that CELC could be a new class of biological relevant material.

Flicking technique for microencapsulation of cells in calcium alginate leading to the microtissue formation.

Microbeads have wide applications in biomedical engineering field that include drug delivery, encapsulation of biomolecules, tissue padding and tissue regeneration. In this paper, we report a simple, yet efficient, flicking technique to produce microcapsules of calcium alginate at a narrow distribution of size. The system consists of an infusion pump and a customised flicker that taps the syringe needle for dispersing microcapsules of sodium alginate that polymerised in the calcium chloride solution. The flow rate of the syringe pump and the velocity of the flicker were studied to achieve a well controlled and tunable size distribution of microbeads ranging from 200 to 400 μm. At a flow rate of 4 μl/min and flicking rate of 80 rpm, a narrow size distribution of microbeads were produced. Via this technique, HaCaT cells were encapsulated in calcium alginate microbeads that grown into microtissues with a size ranging from 100 to 300 μm after two weeks of culture. These microtissues could be potentially useful for pharmacological application.

A scaffoldless technique for self-generation of three-dimensional keratinospheroids on liquid crystal surfaces.

We describe a new scaffold-free three-dimensional (3D) cell culture model using cholesteryl ester based lyotropic liquid crystal (LC) substrates. Keratinocytes were deposited randomly on the LC surface where they self-assembled into 3D microtissues or keratinospheroids. The cell density required to form spheroids was optimized. We investigated cell viability using dead/live cell assays. The adhesion characteristics of cells within the microtissues were determined using histological sectioning and immunofluorescence staining. Fourier transform infrared spectroscopy (FTIR) was used to characterize the biochemistry of the keratinospheroids. We found that both cells and microtissues could migrate on the LC surface. The viability study indicated approximately 80% viability of cells in the microtissues up to 20 days of culture. Strong intercellular adhesion was observed in the stratification of the multi-layered microspheroids using field emission-scanning electron microscopy (FE-SEM) and histochemical staining. The cytoskeleton and vinculins of the cells in the microtissues were expressed diffusely, but the microtissues were enriched with lipids and nucleic acids, which indicates close resemblance to the conditions in vivo. The basic 3D culture model based on LC may be used for cell and microtissue migration studies in response to cytochemical treatment.

Design of an efficient back-drivable semi-active above knee prosthesis

This paper presents the design and development of an electrical above knee prosthesis, which works as a passive knee prosthesis in part of gait cycle phases and as an active knee prosthesis during other portions. During the passive mode, the system works as a non-holonomic system, and the dynamic coupling between the thigh segment and the knee prosthesis is used to control the prosthesis. Therefore, this knee prosthesis is designed to be back-drivable in passlve mode. In order to present a proper design for the knee prosthesis, the mechanism synthesis and analysis for the proposed back-drivable semi-active knee prosthesis are covered in this paper.

Tracking Traction Force Changes of Single Cells on the Liquid Crystal Surface

Cell migration is a key contributor to wound repair. This study presents findings indicating that the liquid crystal based cell traction force transducer (LCTFT) system can be used in conjunction with a bespoke cell traction force mapping (CTFM) software to monitor cell/surface traction forces from quiescent state in real time. In this study, time-lapse photo microscopy allowed cell induced deformations in liquid crystal coated substrates to be monitored and analyzed. The results indicated that the system could be used to monitor the generation of cell/surface forces in an initially quiescent cell, as it migrated over the culture substrate, via multiple points of contact between the cell and the surface. Future application of this system is the real-time assaying of the pharmacological effects of cytokines on the mechanics of cell migration.

In Vitro Growth of Human Keratinocytes and Oral Cancer Cells into Microtissues: An Aerosol-Based Microencapsulation Technique

Cells encapsulation is a micro-technology widely applied in cell and tissue research, tissue transplantation, and regenerative medicine. In this paper, we proposed a growth of microtissue model for the human keratinocytes (HaCaT) cell line and an oral squamous cell carcinoma (OSCC) cell line (ORL-48) based on a simple aerosol microencapsulation technique. At an extrusion rate of 20 μL/min and air flow rate of 0.3 L/min programmed in the aerosol system, HaCaT and ORL-48 cells in alginate microcapsules were encapsulated in microcapsules with a diameter ranging from 200 to 300 μm. Both cell lines were successfully grown into microtissues in the microcapsules of alginate within 16 days of culture. The microtissues were characterized by using a live/dead cell viability assay, field emission-scanning electron microscopy (FE-SEM), fluorescence staining, and cell re-plating experiments. The microtissues of both cell types were viable after being extracted from the alginate membrane using alginate lyase. However, the microtissues of HaCaT and ORL-48 demonstrated differences in both nucleus size and morphology. The microtissues with re-associated cells in spheroids are potentially useful as a cell model for pharmacological studies.

A study on the ergonomic assessment in the workplace

Ergonomics has gained attention and take into consideration by the workers in the different fields of works recently. It has given a huge impact on the workers comfort which directly affects the work efficiency and productivity. The workers have claimed to suffer from the painful postures and injuries in their workplace. Musculoskeletal disorders (MSDs) is the most common problem frequently reported by the workers. This problem occurs due to the lack of knowledge and alertness from the workers to the ergonomic in their surroundings. This paper intends to review the approaches and instruments used by the previous works of the researchers in the evaluation of the ergonomics. The two main assessment methods often used for ergonomic evaluation are Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA). Popular devices are Inertial Measurement Units (IMU) and Microsoft Kinect.

Development of a Microfluidic Vibrational Cleaning System for Cleaning Microtissues

Microtissues can be cultured on the hydrogel, liquid crystal substrate and scaffolds. Therefore, a cleaner has been developed to clean the microtissue extracted from the culture substrate such as the cholesteryl ester liquid crystal (CELC). Clean microtissue samples were required for the precise experimental output. The cleaner performance was verified by observing the CELC’s birefringence properties around microtissue through cross-polarising microscope. In addition, the effects of mechanical vibration that generated by the microtissue cleaner onto the microtissue sample were investigated by live/dead cells assay. Based on the results, 3D microtissue cleaner was effectively cleaned microtissue after three replicated cleaning steps. Two minutes of continuous vibration frequency at 148 Hz and acceleration of 0.89 Grms were suitable to clean the microtissue.

Development of a Microfluidic Device System Using Adhesive Vinyl Template to Produce Calcium Alginate Microbeads for Microencapsulation of Cells

Microfabrication technique based on microelectronic technology is commonly used to produce microfluidic devices but this technique involves with costly and toxic chemicals. In this paper, we proposed the use of patterned adhesive vinyl template to produce a poly-dimethylsiloxane (PDMS) microfluidic device that was applied to generate microbeads of calcium alginate for microencapsulation of cells. In the microfluidic system, an infusion pump of high flow rate (2000 µl/min) and a commercial syringe pump were used to emulsify the continuous and disperse phases of liquids in forming the microbeads. Microbeads of calcium alginate in the range of 438 ± 38–799 ± 20 µm were successfully produced using this environmental friendly technique.

Development of a Mechatronic Syringe Pump to Control Fluid Flow in a Microfluidic Device Based on Polyimide Film

With the advancement in microfluidic technology, fluid flow control for syringe pump is always essential. In this paper, a mechatronic syringe pump will be developed and customized to control the fluid flow in a poly-dimethylsiloxane (PDMS) microfluidic device based on a polyimide laminating film. The syringe pump is designed to drive fluid with flow rates of 100 and 1000 μl/min which intended to drive continuous fluid in a polyimide based microfluidic device. The electronic system consists of an Arduino microcontroller board and a uni-polar stepper motor. In the system, the uni-polar stepper motor was coupled to a linear slider attached to the plunger of a syringe pump. As the motor rotates, the plunger pumps the liquid out of the syringe. The accuracy of the fluid flow rate was determined by adjusting the number of micro-step/revolution to drive the stepper motor to infuse fluid into the microfluidic device. With the precise control of the electronic system, the syringe pump could accurately inject fluid volume at 100 and 1000 μl/min into a microfluidic device.