Quartz crystal microbalance for the detection of microgram quantities of human serum albumin: relationship between the frequency change and the mass of protein adsorbed

Abstract

We have developed a piezoelectric immunosensor for the detection of microalbumin. Human serum albumin (HSA) in the range 0.1-100 micrograms mL-1 could be detected using a flow cell; the immunosensor is sensitive enough to monitor levels of albuminuria. The immunosensor did not respond to bovine serum albumin, only to HSA, implying that the specificity for HSA was high. We investigated the relationship between the frequency change (delta F) and adsorption per unit area of piezoelectrically active quartz crystal (delta M). delta M was estimated with radioisotope-labeled anti-HSA or HSA. When anti-HSA was adsorbed onto the surface of the crystal or HSA was bound to anti-HSA supported by the crystal, values of magnitude of delta F/delta M were larger than the value predicted from theory (Sauerbrey's equation). Furthermore, magnitude of delta F/delta M for HSA was larger than that for anti-HSA.

Fluorescence modulation sensing of positively and negatively charged proteins on lipid bilayers

“…As such, it may serve as a screen for monitoring protein-ligand interactions in biophysical assays of membranes. Further quantification of this technique should be possible by exploiting QCM-D [3][4][5][6] or SPR [7][8][9][10] as complementary approaches to help determine the number density of analyte proteins and perhaps even the charge per analyte. Moreover, complementary techniques may also help quantify potential interference effects and related platform biofouling effects when more complex, real-world biological samples are analyzed.…”

“…Dye labels can, however, interfere with analyte activity and be difficult to efficiently employ [1,2]. Many sensing techniques have consequently been developed such as quartz-crystal microbalance (QCM), [3][4][5][6] surface plasmon resonance (SPR), [7][8][9][10] semiconductor nanowire conductivity, [11,12] and optical microcavities that avoid the use of fluorescent labels [13]. Although these techniques avoid the problems associated with directly attaching fluorescent tags to analytes, they can behave non-linearly in response to analyte concentration, require specialized equipment or procedures which can be difficult and/or costly to employ, or possess poorer detection limits than fluorescence-based techniques.…”

Capabilities of Piezoelectric Immunosensors for Detecting Infections and for Early Clinical Diagnostics

“…This is due to rather mild conditions of protein immobilization, but the stability of the film coating is low, the mass of the bio-layer is already lower after 2 -4 measuring cycles. Immunosensors (Muratsugu et al 1993) make it possible to determine HSA with high sensitivity and selectivity in the range of 0.1 -100 µg·ml -1 even in the presence of a nonspecific impurity protein -bovine serum albumin (BSA). Further development of immobilization methods was aimed at increasing the strength of the bio-layer due to a substrate on the basis of calixarenes and synthetic polymers (Sakti et al 2001), which ensures the sensor's long-term operation in analyzing not only sample solutions but real samples of biological fluids (e.g., urine).…”

Piezoelectric chemical sensors (IUPAC Technical Report)

“…Comment: The use of the practical response time, defined as the time elapsing between the instant at which the environment of the piezoelectric sensor is changed and the first instant at which the measured signal of the piezoelectric sensor becomes equal to a fixed value (t*) or reaches a given fraction of the total expected change of the measured variable (e.g., 95 %, t 95 ), requires initial knowledge of a new steady-state value which, however, may not be available. Nevertheless, specific values of ∆f/∆t can be related to t 95 or t* through mathematical models, provided that longterm frequency or phase-determining processes have been identified. However, it seems doubtful that relationships fully describing practical response times can be derived, in view of different functional dependencies that characterize responses of the piezoelectric sensors, both at shortand long-time domains.…”

“…EQCM has been applied in diverse fields of science and technology, such as membrane research [80], metal deposition [81], electroplating [82], electrosorption [83][84][85][86][87], underpotential deposition [88,89], adsorption of biologically active materials [90], biofilms [91], layered nanostructures [92], drug delivery [93], analytical determination of small ions and biomolecules [12,95], self-assembling monolayers [12,[96][97][98], electrochemical oscillations [99][100][101][102], conducting salts [103], semiconductors [104], batteries [105], and corrosion [106][107][108][109]. EQCM has been combined with rotating disc electrode [110], probe beam deflection [111], scanning electrochemical microscopy [111], or differential electrochemical mass spectrometry [112].…”