Djoko H Santjojo

Functionality of ZnPc Thin Film Deposited on Polystyrene Interlayer for Immobilization of Biomolecules in QCM Based Biosensor

Functionality of zinc pthalocyanine (ZnPc) thin film for immobilization of biomolecules was studied using bovine serum albumin (BSA). The functionality is affected by microstructures and surface roughness of the film. This studies is conducted by producing ZnPc films by means of thermal evaporation in vacuum. The ZnPc films were deposited on quartz crystal substrates with a polystyrene interlayer. Observations were carried out using a scanning electron microscope and an optical micro-profilometry. Enhancement of the functionality is observed with the increase of the film thickness. Surface roughness and microstructures of the film influence the functionality in a complex way. Adsorbtion of the BSA molecules is associated with both the surface roughness and microstructures. Although generally the adsorption is proportional to the contact area but the roughness and fibrous microstructures of the deposited ZnPc produce complex adsorption and trapping mechanisms in the immobilization of the BSA.

Identification of pulse frequency spectrum of chronic kidney disease patients measured at TCM points using FFT processing

Mortality due to chronic kidney disease (CKD) increases significantly in a recent year. The disease often is diagnosed in an advanced stage. On the other hand, there has been traditional Chinese method or technique to diagnose the presence of the CKD. The diagnosis is carried out by examining pulse palpation at three points namely cun, guan and chi located at the radial artery of the left hand. Records of the pulse pattern of the CKD patients showed irregular characteristics compared with regular pattern obtained from healthy subjects. The aim of this study was to determine the relationship between the frequency spectrum of the irregular pulses related to the stages of the CKD especially from the chi area. Data of the irregular pulse were categorized into 6 stages i.e. 1, 2, 3a, 3b, 4, and 5 of the CKD patients. The data were collected by measuring pressure during systolic periods or when blood vessels were in a relaxed state. In this period, the instrumentation records reflections of the pulse including information about the amplitudes, frequencies, and pulse wave patterns. Observations were focused on the part of the signal between low and high amplitude on pulse patterns (systolic period). The irregular patterns were processed by a Fast Fourier Transform (FFT) technique to find out their special characteristics quantitatively. Results showed that the pattern irregularity was related to the severity of the kidney dysfunction. The FFT processing results showed a number of different special characters in the spectrum. The data were clustered related to the CKD stages. The clustered data of the CKD patients indicates a correlation between the stages and the shifting of the spectrum to lower frequencies which are 0.26 Hz compared to health subjects data 1.11 Hz.

Synthesis of ZnPc functional layer on QCM biosensor with polystyrene interlayer by means of evaporation techniques

A ZnPc functional layer has been successfully synthesized on QCM biosensor with polystyrene interlayer. Two evaporation techniques were utilized to deposit the ZnPc on the polystyrene interlayer i.e. liquid evaporation technique and solid evaporation technique. Deposition parameters of each technique affect the thickness and microstructure of layer. Islands structures were produced by liquid evaporation, while fibrous structure was produced by solid evaporation technique.The islands grown from 1,00% ZnPc consist of platelets arranged vertically to the surface. The islands consisting pillars of crystal was obtained from 1,25% ZnPc, while the 1,50% ZnPc produces islands consisting granules. The structures might be related to the composition of the crystals. The fibrous structures are controlled by evaporation rate of the ZnPc.

Effect of Xylene and Tetrahydrofuran Solvent Type on Polystyrene Layer Thickness With Spin Coating Method

Surface modification of QCM by applying polystyrene (Ps) as a coating layer has been investigated. The PS layer was coated onto QCM sensor by using spin coating method. Polystyrene was dissolved in two different solvents i.e., xylene and Tetrahydrofuran (THF) with various concentration i,e 1%, 2%, 3%, 4%, 5% and the velocity angular of spin coater were 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, dan 4000 rpm. The results show that different solvent result in the difference of thickness of polystyrene coating layer. By calculation with the Sauerbrey equation, the thickness of Ps layer using xylene solvent show 0.1 µm, 0.28 µm, 0.35 µm, 0.59 µm, and 0.81 µm. While by using THF, the thickness of each Ps layer are 0.15 µm, 0.43 µm, 0.84 µm, 0.97 µm, 1.28 µm. On the other hand, by applying different velocity of spin coater, the thickness of polystyrene with xylene are 0.486 µm, 0.445 µm, 0.432 µm, 0.350 µm, 0.320 µm, 0,290 µm, respectively. Moreover, the thickness of PS layer by using THF show 1.05 µm, 0.93 µm, 0.87 µm, 0.84 µm, 0.67 µm, 0.52 µm. Vapor pressure of each solvent is considered as the main property of solvent which influence the thickness of coating. The vapor pressure of THF (143 mmHg) is higher than the vapor pressure of xylene (72 mmHg), the thickness Ps layer with THF is thicker than that of by xylene solvents.