Quantum dot–Cramoll lectin as novel conjugates to glycobiology

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2018-01, Vol.178, p.85-91
• Main Authors: Cunha, Cássia R.A., Andrade, Camila G., Pereira, Maria I.A., Cabral Filho, Paulo E., Carvalho, Luiz B., Coelho, Luana C.B.B., Santos, Beate S., Fontes, Adriana, Correia, Maria T.S.
• Format: Article
• Language: English
• Subjects: Adsorption; Anticancer properties; Bioconjugation; Biological activity; Biological properties; Biology; Biomolecules; Cancer; Candida albicans; Carbohydrates; Conjugates; Conjugation; Cytometry; Flow cytometry; Fluorescence; Fluorescence microscopy; Glycoconjugate; Glycosylation; Hemagglutination; Hydrogen ions; Immunomodulation; Labeling; Lectins; Mannose; Microorganisms; Nanoparticles; Optical properties; Pathogenicity; Pathogens; pH effects; Proteins; Quantum dots
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2017.10.020

The optical properties of quantum dots (QDs) make them useful tools for biology, especially when combined with biomolecules such as lectins. QDs conjugated to lectins can be used as nanoprobes for carbohydrate expression analysis, which can provide valuable information about glycosylation changes related to cancer and pathogenicity of microorganisms, for example. In this study, we evaluated the best strategy to conjugate Cramoll lectin to QDs and used the fluorescent labeling of Candida albicans cells as a proof-of-concept. Cramoll is a mannose/glucose–binding lectin with unique biological properties such as immunomodulatory, antiparasitic, and antitumor activities. We probed covalent coupling and adsorption as conjugation strategies at different pH values. QDs conjugated to Cramoll at pH7.0 showed the best labeling efficiency in the fluorescence microscopy analysis. Moreover, QD-Cramoll conjugates remained brightly fluorescent and preserved identical biological activity according to hemagglutination assays. Flow cytometry revealed that approximately 17% of C. albicans cells were labeled after incubation with covalent conjugates, while approximately 92% of cells were labeled by adsorption conjugates (both at pH7.0). Inhibition assays confirmed QD-Cramoll specificity, which reduced the labeling to at most 3%. Therefore, the conjugates obtained by adsorption (pH7.0) proved to be promising and versatile fluorescent tools for glycobiology. [Display omitted] •Covalent coupling or adsorption was probed to conjugate QD with Cramoll lectin.•The best conjugation strategy was evaluated by the labeling of C. albicans cells.•The adsorption at pH7.0 was a superior strategy for QD-Cramoll lectin conjugation.•QD-Cramoll conjugates provided a homogenous, effective and bright labeling.•QD-Cramoll conjugates are versatile tools for carbohydrate expression studies.