One- and Two-Photon Excited Optical pH Probing for Cells Using Surface-Enhanced Raman and Hyper-Raman Nanosensors

• Published in: Nano letters 2007-09, Vol.7 (9), p.2819-2823
• Main Authors: Kneipp, Janina, Kneipp, Harald, Wittig, Burghardt, Kneipp, Katrin
• Format: Article
• Language: English
• Subjects: Animals; Biosensing Techniques - instrumentation; Biosensing Techniques - methods; Condensed matter: structure, mechanical and thermal properties; Equipment Design; Equipment Failure Analysis; Exact sciences and technology; General equipment and techniques; Hydrogen-Ion Concentration; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Mice; Microscopy, Fluorescence, Multiphoton - instrumentation; Microscopy, Fluorescence, Multiphoton - methods; Nanotechnology - instrumentation; Nanotechnology - methods; NIH 3T3 Cells; Physics; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Spectrum Analysis, Raman - instrumentation; Spectrum Analysis, Raman - methods; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl071418z

We demonstrate spatially resolved probing and imaging of pH in live cells by mobile and biocompatible nanosensors using surface-enhanced Raman scattering (SERS) of 4-mercaptobenzoic acid (pMBA) on gold nanoaggregates. Moreover, we also show that this concept of pH nanosensors can be extended to two-photon excitation by using surface-enhanced hyper-Raman scattering (SEHRS). In addition to the advantages of two-photon excitation, the SEHRS sensor enables measurements over a wide pH range without the use of multiple probes.