Effective antibodies immobilization and functionalized nanoparticles in a quartz-crystal microbalance-based immunosensor for the detection of parathion.
BACKGROUND
Biosensor-based detection provides a rapid and low-cost alternative to conventional analytical methods for revealing the presence of the contaminants in water as well as solid matrices. Although important to be detected, small analytes (few hundreds of Daltons) are an issue in biosensing since the signal they induce in the transducer, and specifically in a Quartz-Crystal Microbalance, is undetectable. A pesticide like parathion (M = 292 Da) is a typical example of contaminant for which a signal amplification procedure is desirable.


RESULTS
The ballasting of the analyte by gold nanoparticles has been already applied to heavy target as proteins or bacteria to improve the limit of detection. In this paper, we extend the application of such a method to small analytes by showing that once the working surface of a Quartz-Crystal Microbalance (QCM) has been properly functionalized, a limit of detection lower than 1 ppb is reached for parathion. The effective surface functionalization is achieved by immobilizing antibodies upright oriented on the QCM gold surface by a simple photochemical technique (Photonic Immobilization Technique, PIT) based on the UV irradiation of the antibodies, whereas a simple protocol provided by the manufacturer is applied to functionalize the gold nanoparticles. Thus, in a non-competitive approach, the small analyte is made detectable by weighing it down through a "sandwich protocol" with a second antibody tethered to heavy gold nanoparticles. The immunosensor has been proved to be effective against the parathion while showing no cross reaction when a mixture of compounds very similar to parathion is analyzed.


CONCLUSIONS
The immunosensor described in this paper can be easily applied to any small molecule for which polyclonal antibodies are available since both the functionalization procedure of the QCM probe surface and gold nanoparticle can be applied to any IgG, thereby making our device of general application in terms of target analyte.
Department of Physics "Ettore Pancini", University of Naples "Federico II", Naples, Italy.
Bartolomeo
B
Della Ventura
Department of Agriculture, University of Naples "Federico II", Portici, Italy.
Marco
M
Iannaccone
Department of Physics "Ettore Pancini", University of Naples "Federico II", Naples, Italy.
Riccardo
R
Funari
Division of Physics and Applied Physics, School of Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.|CNR-SPIN, University of Naples "Federico II", Naples, Italy.
Massimo
M
Pica Ciamarra
Department of Physics "Ettore Pancini", University of Naples "Federico II", Naples, Italy.
Carlo
C
Altucci
Department of Agriculture, University of Naples "Federico II", Portici, Italy.
Rosanna
R
Capparelli
Department of Agriculture, University of Naples "Federico II", Portici, Italy.
Sante
S
Roperto
Department of Physics "Ettore Pancini", University of Naples "Federico II", Naples, Italy.
Raffaele
R
Velotta
D000327:Adsorption; D055910:Antibodies, Immobilized / Q000378:metabolism / Q000494:pharmacology; D000918:Antibody Specificity; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D006046:Gold / Q000737:chemistry; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D010278:Parathion / Q000032:analysis* / Q000302:isolation & purification; D010575:Pesticides / Q000032:analysis* / Q000302:isolation & purification; D011791:Quartz / Q000737:chemistry; D058525:Quartz Crystal Microbalance Techniques / Q000295:instrumentation / Q000379:methods
D055910:Antibodies, Immobilized; D010575:Pesticides; D011791:Quartz; D010278:Parathion; D006046:Gold