ABSTRACT
In a broad sense, the term biophotonics refers to the use of light (photons) to investigate biological processes (Fig. 8.1.1a). Culminating in
a research area that intersects biology, chemistry, physics, and engi-
neering, biophotonics has allowed many optical science and techno-
logical developments to bring new insights into life sciences for both
fundamental and clinical interests. For instance, transmission light
microscopy combined with various contrast enhancement methods
(e.g., phase contrast or differential interference contrast) is widely
adopted to observe tissues, cells and organelles. Spectroscopy
(e.g., absorption, luminescence, infrared, or Raman spectroscopies)
permits measurements of sample concentration and identification
of material contents [1]. Fluorescent probes (e.g., organic dyes,
quantum dots and fluorescent nanodiamonds) have enabled mole-
cular imaging and have gained considerable attention because
of their molecular-level sensitivities and multiplexing capabilities
[2-6]. Together with fluorescent protein reporters, fluorescence
microscopy and high-throughput fluorescence-activated cell sorting
techniques are routinely used in real-time monitoring of gene
expression and regulation in single cells [2, 7]. In addition to the
characterization of biological materials, the term biophotonics can also refer to optical techniques that physically or genetically control
specimens. In fact, since the first demonstration of the laser in
the 1960s, progress in laser development has not only impacted
our lives through improved microscopy or spectroscopy techniques
but has also enabled unprecedented manipulation and actuation of
materials of a diverse range For example, photodynamic therapy
is widely used to guide and activate chemical compounds for drug
release [8]. Additionally, optical tweezers that employ highly focused
laser beams can individually trap micrometer-sized objects [9].
Such actuators also enable measurements of the force generated by
biomolecular interactions at the piconewton scale to investigate the
biophysics of single molecules More recently, optogenetic control
was demonstrated to allow manipulation through guided light [10,
11]. This report opened up new venues for researching biological
events in live cells One common theme for both light-enabled
imaging and actuation is that the photonic system in question must
allow for light collection and manipulation within the length and
time scale of biological interest.
