Nanowire lasers as intracellular probes

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Optical Physics

Background:

• Intracellular sensing requires probes with high sensitivity and specificity.
• Existing methods for intracellular measurements face limitations in resolution and invasiveness.
• Nanowire (NW) lasers offer potential for miniaturized, sensitive optical probes.

Purpose of the Study:

• To investigate the feasibility of using a cadmium sulfide (CdS) nanowire (NW) laser as a stand-alone intracellular probe.
• To demonstrate the NW laser's ability to perform sensitive measurements within a single cell.
• To evaluate the performance metrics of the NW laser for intracellular sensing applications.

Main Methods:

• Fabrication and characterization of CdS NWs.
• Spontaneous internalization of CdS NWs into single cells.
• Optical pumping of internalized NWs using nano-joule light pulses.
• Monitoring of laser emission characteristics (wavelength, linewidth).
• Analysis of lasing peak wavelength shifts in response to intracellular refractive index changes.

Main Results:

• Successful spontaneous internalization of CdS NWs into single cells.
• Observation of green laser emission (500-520 nm) from intracellular NWs.
• Achieved narrow peak linewidth as low as 0.5 nm.
• Demonstrated high sensitivity of 55 nm/RIU for detecting intracellular refractive index changes.
• Reported a figure of merit of approximately 98 for the NW laser probe.

Conclusions:

• CdS NW lasers can function as effective, self-contained intracellular probes.
• The sub-micron diameter of NWs enables sensitive detection via evanescent field interactions.
• This technology holds promise for advanced intracellular sensing and diagnostics.