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  • Using protein-encapsulated ...
    Selvaprakash, Karuppuchamy; Chen, Yu-Chie

    Biosensors & bioelectronics, 11/2014, Letnik: 61
    Journal Article

    In this study, we generated gold nanoclusters (AuNCs) using inexpensive chicken egg white proteins (AuNCs@ew) as reagents. AuNCs@ew were generated by reacting aqueous tetrachloroauric acid with diluted chicken egg white under microwave heating (90W) through subsequent heating cycles (5min/cycle). Within 10 cycles, red photoluminescent AuNCs@ew with maximum emission wavelength at ~640nm (λex=370nm) were obtained. The quantum yield of the as-generated AuNCs was ~6.6%. The intact and the tryptic digest of AuNCs@ew were characterized by mass spectrometry. The results showed that the AuNCs@ew were mainly derived from ovalbumin, i.e., the major protein in egg white, encapsulated AuNCs. The AuNCs@ew also has the common features found in AuNCs@protein, which is sensitive to the presence of heavy metal ions such as Cu2+. The photoluminescence of the AuNCs@ew was quenched with the addition of Cu2+. Furthermore, the photoluminescence of the quenched AuNCs@ew can be restored in the presence of the molecules containing phosphate functional groups because of the strong binding affinity between Cu2+ and phosphates. We used the AuNCs@ew-Cu2+ conjugates as switch-on sensing probes for the detection of phosphate containing metabolites such as adenosine-5′-triphosphate (ATP) and pyrophosphate (PPi). The results showed that the photoluminescence of the sensing probes increased as the concentration of the phosphate-containing molecules in the sample solution increased. The limits of detection achieved using the AuNCs@ew-Cu2+ for ATP and PPi were ~19 and ~5μM, respectively. Additionally, we also demonstrated the feasibility of using the AuNCs@ew as the sensing probes for lectins such as concanavalin A (Con A) based on the molecular recognitions between the glycan ligands on the AuNCs@ew and glycan binding sites on Con A. •Chicken egg white (ew) protein-directed syntheses of AuNCs were demonstrated.•The generated AuNCs were mainly encapsulated by chicken egg ovalbumin.•The generated AuNCs@ew is quenched in the presence of Hg(II) and Cu(II).•The AuNCs@ew-Cu(II) conjugates are useful switch-on sensing probes for ATP and PPi.•The AuNCs@ew can be used to recognize Con A based on the molecular recognition.