Applications of Biophotonics in Space

Physics is a fascinating science that plays a significant role in our understanding of the universe. It comprises of the study of matter, its constituents, and their motion through space and time, and is one of the five natural sciences that help us define the world around us.

The world of physics is very broad and can be divided into multiple disciplines including, but not limited to, mechanics, electromagnetism, relativity, and most relevant to our topic, optics. In short, optics is the study of light.

In longer terms, it is a branch of physics that is concerned with electromagnetic waves and their properties and interactions with matter, as well as the manipulation of these waves. This branch tells us everything we know about vision, lasers, telescopes, microscopes, the color of the sky and rainbow, the twinkling of stars, and many more!

Optics itself can also be split into three major branches – physical, geometrical, and quantum optics. Geometrical, or classical, optics studies the manipulation of light using devices such as lenses, mirrors, and prisms. A primary application of geometrical optics is imaging lens design for cameras.

Physical optics deals with the wave nature of light rather than its particle nature in order to study effects like interference and diffraction for applications like the production of holographic images. Quantum optics, on the other hand, is the study of the particle nature of light to probe properties that are used in applications of light creation at p-n semiconductor junctions inside LEDs.

What is photonics?

Photonics is a subcategory of optics that primarily studies the detection, generation, and manipulation of photons, the building blocks of light waves, through certain technologies.

An important distinction between optics and photonics is the scope, where optics is more theoretical, while photonics applies optical principles to develop devices and systems used in various applications that surround us in our everyday lives like telecommunications, medical applications, sensing, and imaging.

Diving deeper into photonics, one innovative discipline is BioPhotonics, which utilizes photonic technologies and optical principles to probe biological samples and solve biological problems.

BioPhotonics essentially studies the interaction between electromagnetic radiation and biological materials like tissues, cells, and even subcellular structures and molecules in living organisms. One of the main advantages of using photonics in biological samples is the non-invasive nature of examined materials. Some interesting applications of BioPhotonics are used in space.

Applications of BioPhotonics in space?

Biomedical Imaging

Biomedical imaging is the process of using photonics techniques to image internal anatomic structures in living organisms. With the advent of space missions in this era, it has become necessary to monitor astronaut’s health and diagnose potential risks.

The only biomedical imaging technique currently used in space is ultrasound devices, to diagnose and monitor medical issues that occur in astronauts due to the harsh environment of space. Uses of ultrasound devices in space include monitoring of musculoskeletal health that might deteriorate due to low gravity, cardiovascular function, and soft tissue injuries.

Ultrasound devices have proved to be more useful in space since they are more compact, portable, and lack ionizing radiation, unlike X-rays or MRI scans. Ultrasound devices also give real-time feedback, allowing astronauts to assess their health without long processing times. [1]

Another application of BioPhotonics in the space sector is the usage of two-photon microscopy to detect bone loss. One of the more serious side effects of extended space flight is a harmful physiological effect, which is accelerated bone loss because of microgravity.

The Bone loss in hips and spine can be up to 1% per month. Two-photon microscopy can be used to probe the condition. Two-photon microscopy is a powerful imaging technique that utilizes two photons of lower energy to excite fluorophores within a specimen simultaneously, leading to fluorescence emission.

This process allows for deeper tissue penetration and reduced phototoxicity compared to traditional fluorescence microscopy techniques.

Two-photon microscopy can provide high-resolution imaging of bone microstructure, allowing researchers to study changes in bone architecture and mineralization associated with bone loss in microgravity. This technique enables visualization of individual bone cells, such as osteoblasts, and osteoclasts, as well as their interactions within the bone matrix [2].

Image-1. Biophotonics and Bone Biology (Image Credit: David Fischer, NASA Glenn Research Cente)

Spectroscopy

Broadly, spectroscopy is the study of the interaction of light and matter, and matter’s ability to absorb or emit electromagnetic radiation. By dispersing light into its constituent wavelengths, spectroscopy allows scientists to examine the unique spectral signatures associated with different elements and molecules.

Raman spectroscopy, one relevant spectroscopy technique involves irradiating a sample with a laser and measuring the scattered light as a spectrum that gives information about the molecules in the sample and the chemical bonds.

Back to astronauts and space missions, Raman spectroscopy is used to quickly identify and characterize microbial contaminations in spacecraft since microbial cells have special Raman spectra that act as identifying fingerprints.

This information is used to ensure the safety of the spacecraft crew and prevent infections during long-duration space missions. Said spacecraft acts as a confined system that is inhabited by a changing microbial consortium, mostly originating from life-supporting devices, equipment collected in pre-flight conditions, and crewmembers.

One of humanity’s most pressing questions is the existence of life outside our planet. To help study this possibility, astronomers use spectroscopy techniques to analyze the absorption and emission lines in a planet’s spectrum, which aids in deducing the atmosphere of far-away planets.

Analyzing the atmosphere can give a great deal of information about the planet’s habitability and the possibility of hosting life, through the detection of molecules that are closely bound to life.

Therapeutic Applications

Nowadays, pharmaceuticals play an extremely important role in curing humans from various illnesses and injuries in an effective yet easy way. The advantages of pharmaceuticals can even reach space as astronauts, especially on long missions, have a growing need for therapeutics to ensure their well-being.

BioPhotonics plays an important role in research that addresses this concern through photodynamic therapy (PDT). Photodynamic therapy can be used to treat infections, injuries, and wounds by utilizing drugs that are sensitive to specific light wavelengths, allowing selective targeting and destruction of damaged cells through non-invasive means.

This type of therapy uses photosensitizing agents that, after accumulating in target tissues, produce reactive oxygen species that kill the cells when they are exposed to specific light wavelengths. PDT is conventionally used to treat various cancers, skin conditions, and microbial infections.

In addition, the Kristallizator program developed by the State Space Corporation Roscosmos has successfully produced single protein crystals that are ideal for X-ray diffraction analysis.

Through these studies, scientists have been able to identify the structure of a target protein for anti-tuberculosis drugs. This breakthrough discovery has the potential to aid in the development of effective treatments for tuberculosis.

Biosensing

Biosensing is the process of detecting and measuring biological molecules / organisms, like proteins, DNA, cells, and pathogens. This process is usually done through the interaction between a biological molecule and the sensor.

One of the abilities of such biosensors is the generation and detection of optical signals that can be analyzed to provide information about the concentration present or activity of the sample. Some space missions in low earth orbit involve studying the effects of deep space on biological samples.

An example of such research involves using dielectric spectroscopy to study the effects of microgravity and radiation on biological samples. This method takes advantage of a common technique used in industrial fermentation processes to measure changes in cell physiology.

Image-2. Protein crystals form in microgravity in the space station’s Kibo Module. (Image Credit: JAXA)

It utilizes the understanding that cells can be polarized when exposed to an electric field, and their ability to be polarized changes the overall capacitance of the cell suspension, which can then be measured at a range of different frequencies.

Capacitance changes as the cells undergo growth, replication, protein synthesis, increases in cell membrane size, and changes in cell shape. Dielectric spectroscopy correlates such cellular changes to capacitance measurements and is one of many methods of measuring biologically relevant data in space that can be miniaturized and automated.