Adhesion microscope slides also known as adhesive or positively charged slides are specially treated to improve the adhesion of biological specimens to the microscope slide. Adhesion slides are commonly used within Histology, Cytology, Immunohistochemistry (IHC) and In Situ Hybridization (ISH) applications; adhering specimens such as tissue sections, cells and cytological preparations to slide surfaces ensuring they remain firmly attached during processes such as washing, heating and staining.
Slide Surface Treatment
Positively charged microscope slides undergo chemical treatments that coat the slide with a layer of positively charged molecules on the surface. Treatments include:
Poly-L-Lysine Coating: Poly-L-lysine is a synthetic amino acid polymer that consists of multiple lysine residues. Lysine is a positively charged amino acid, and when polymerized, it creates a surface with a high density of positive charges. The slides are coated with a solution of Poly-L-lysine, which can be done by dipping the slides in the solution or applying the solution directly to the slides and allowing them to dry.
Silane: Silane compounds, such as aminoalkylsilane and 3-aminopropyltriethoxysilane (APTES) are used to immerse microscope slides into and modify the slide surface with positively charged aminos. The silane molecules form a bond with the hydroxyl groups on the glass surface to create an adhesion for biological specimens.
Other Proprietary Coatings: Various manufacturers also have their own proprietary coatings that create a positively charged surface.
Electrostatic Attraction
Biological tissues and cells often have negatively charged components due to the presence of phosphate groups in nucleic acids (DNA/RNA), and carboxyl groups in proteins and cell membranes (Phospholipid bilayers). The positively charged surface of the adhesion slide creates an electrostatic bond with these negatively charged molecules, helping to secure the specimen onto the slide.
Applications of Adhesion Slides
Histology: In the preparation of tissue sections for microscopic examination, adhesion slides prevent tissue sections from detaching during deparaffinization, rehydration, and staining.
Cytology: Adhesion slides help ensure cells remain on the slide during staining and analysis for samples such as Pap smears.
Immunohistochemistry (IHC): Adhesion slides help allow the detection of specific antigens in tissue sections during IHC by maintaining the attachment of the sample to the slide during, adhesion slides during rigorous washing and staining protocols.
In Situ Hybridization (ISH): This technique involves hybridizing nucleic acid probes to specific DNA or RNA sequences in tissue sections or cells, in which the negative charges of nucleic acids bond to the slides enabling the sample to withstand multiple washing steps.
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