Applications of Luminescence pdf

Applications of Luminescence Spectroscopy in the field of Bio-imaging

Introduction:

The bio-imaging is a process in which we visualize the activity of biological process in a specific period of time. The bio-imaging process helps us to determine the connection of the tissue structures of  multicellular organisms and  sub cellular structures.

As we observe the fluorescence from the sample in luminescence spectroscopy, this leads to major impact on impact on biomedical research not to visualize the pathobiological life process but also to track single molecules in living structures, replacement of radioactive therapy and detection of diseases. The luminescence spectroscopy is a powerful tool in of research, investigation, analysis, diagnose and control of diseases in biological fields due to development of fluorescent probs which are used for bio-imaging.

The luminescence Spectroscopy gains important in bio-imaging due to high resolution and sensitivity. The image quality of biological living structures depend upon the performance of fluorophores or probes. The low molecular weight dyes , organic ligands complex with lanthanides   are used in bio-imaging of  tissues and cells. Mostt important is discovery of green fluorescent proteins make great progress to bio-imaging of proteins tracking, quantification and sensing. The nanomaterial shows great luminescence properties which include quantum dots, carbon dots, metal doped nanomaterial, organic-inorganic hybrid nanomaterials and especially gold nanoparticles in recent years. The most widely used in luminescence for bio-imaging are semiconductor quantum dots which include Se, CdTe, CdS, ZnS, ZnSe, PbS.

Applications of Luminescence Spectroscopy in bio-imaging:

1.Cell Biology:

  The heterogenous sample of biological fluids have different range of viscocities. This range. This viscosity range is low in cytosol and high in cell membrane environemnts, DNA and protein binding sites. By measuring the intracellular viscosities with the help of fluorescence rotors with high γ-value probes , we can identify different organelles. To get this image , we used in meso substituted Bodipy dye with a rotatable phenyl group (γ =0.5) in luminscenct spectroscopy.

The cell membrane play important role in structure which is composed of  many biological molecules to maintains its structure. Dyes with fluorescence sensitivity are applied to get imaging of the membrane. The proteins at cell levels are important because  of their important role in  cell signaling mechanism, transport between cell and tissues, gene expression, endocytosis and other important functions in cell. For getting image, the most important step is labeling the lipid or protein with gene of interests. This labeling is done by using fluorescent proteins and colocalization with organic dyes and quantum dots. For protein-protein, fluorescent proteins are used commonly. 

2.Imaging of Cancer:

The cells, tissues and whole body imaging is done by using the endogenous fluorophore  in the research in luminescence spectroscopy mehods.

The fluorescence is focused on NAD(P)H autofluorescence to differentiate between the non cancers cells and cancer cells or tissues. For example when, there is decrease in autofluorescence in decrease in autofluorescence fluorescence lifetime at around 450 nm in fibrosarcoma tumor was releated with NADH  from the free state to bound state. The combination of   fluorescence lifetime of NADH with fluorescence intensity comparison to the emission of tryptophan as an internal standard was subjected  to differentiate the cervical cancer cells from the normal cells or tissues.

The fluorescence imaging of skin is done to distinguish between the basal cell carcinomas (BCCs) from surrounding uninvolved skin for early diagnosis of skin cancer. The early luminescence technique to imaging cancers cell have low signal-to-noise ratio caused by weak fluorescence intensity and the  interference from other fluorophores such as high light scattering by the skin  and NAD(P)H. For distinguish of brest cancers cells and normal cells , two photon fluorescence imaging is used to reveal the intracellular NADH around the breast cells and environment.

In another study reported that with  exogeneous dyes, time gated imaging of patient tissues stained with specials stain revealed the specific diagnostic content to  malignant tumors. 

Brain Tissue Bio-imaging:

The Near infrared fluorescent probes are synthezied which shows change in fluorescence when they bind to amyloid-beta peptides. Actually, this is the main constituent of amyloid plaques in the brains of Alzheimer’s patients. When the patient’s blood gave the permeability to these probes, then they provide quantitative determination of molecular imaging of amyloid plaques in vivo with high sensitivity.

Blood Bioimaging:

 Blood vessels, especially larger shows strong autofluorescence originating from both elastin  and collagen. The difference between the segments of blood vessels  rich in elastin can be easily checked on characteristics of fluorescence time. To check the dangerous plaques in body we used the fiber optic devices based on time resolved laser fluorescence spectroscopy. These plaques can rapture and released the contents white blood cells and lipids which cause clotting and lead to heart attack or stroke. So, luminescence spectroscopy is a powerful tool in imaging to identify the dangerous palques with high sensitivity and specificity. 

Drug Delivery and Release:

The antitumor drug doxorubicin which is fluorescence and showed environmental sensitive fluorescence lifetime. The fluorescence lifetime of doxorubicin increases from 1.1 ns in free form to 2.4 ns after binding to DNA which providing a method to Checking and monitoring the release of the drug from a polymeric capsule. To monitor the biodegrade polymeric nanoparticles as modal drug carrier as fluorescence time increases when we use of encapsulated NIR dyes.

Cell Tracking inside living organisms:

It is unique feature of fluorescence imaging in living organism as dendritic cell therapy is to treat cancer and preventing cancer. During this therapy, cells other than nanocaapulses are used as therapeutic vehicle to target tissues. Fluorescence lifetime imaging of dendritic cells labeled internally with NIR-emissive polymersomes enabled cell tracking in vivo. This method or therapy provides a tool to evaluate dendritic-cell-based immunotherapy. It serves as  new effective opportunities for in vivo cell tracking by fluorescence imaging.

Yeast, Bacteria, and Virus Detection:

The bacterial ad viral infections are main caused of diseases in human. So, it is necessary to differentiate the nature of these living organisms, luminescence microscopy is used for imaging and detection of these living organisms. To make the difference between the gram negative and gram positive bacteria, fluorescent lifetime of intrinsic fluorophores such as trytophans are used. To differentiate bacteria active bacteria from inactive bacteria, detection of bacteria on meat, the time resolved fluorescence using intrinsic fluorescence is used. F

Fluorescence imaging is used to find diseases in living organisms and plants . For example, the apple which is contaminated shows excellent visualization with high contrast than the normal apple by fluorescence life time images.

In case of viral infection, the encoded viral genome protease released  into the cytoplasm of the host cell. It  cleaved the protease-sensitive FRET construct composed of fluorescent proteins GFP2 and DsRed2 which is connected by a cleavage protease recognition site. The increase in fluorescence lifetime in result of cleavage which confirms the presence of target virus.  

The optical image is powerful tool in biology for providing the image, detection and screening of diseases in our daily life. This method is mainly based the interaction of light from source to fluorophore. The use of photoluminescence nanoparticles in bio-imaging of  use that wavelength which falls below biological optical transparency windows. In this range ,the light scattering and autofluoroscence is minimized. The main applicatons of luminescence spectroscopy in optical imaging of intracellur, targeting specific tissues and cells, detection of cells.