Growing Applications of “Click Chemistry” for Bioconjugation in Contemporary Biomedical Research

Abstract

Summation This update summarizes the growing application of “click” chemistry in diverse areas such as bioconjugation, drug discovery, materials science, and radiochemistry. This update also discusses click chemistry reactions that proceed rapidly with high selectivity, specificity and yield. Two important characteristics make click chemistry so attractive for assembling compounds, reagents, and biomolecules for pre-clinical and clinical applications. First, click reactions are bioorthogonal; neither the reactants nor their product’s functional groups interact with functionalized biomolecules. Second, the reactions proceed with ease under mild non-toxic conditions such as at room temperature and usually in water. The copper catalyzed Huisgen cycloaddition, azide-alkyne [3+2] dipolar cycloaddition, and Staudinger ligation, azide-phosphine ligation, each possess these unique qualities. These reactions can be used to modify one cellular component while leaving others unharmed or untouched. Click chemistry has found increasing applications in all aspects of drug discovery in medicinal chemistry such as for generating lead compounds through combinatorial methods. Bioconjugation via click chemistry is rigorously employed in proteomics and nucleic research. In radiochemistry, selective radiolabeling of biomolecules in cells and living organisms for imaging and therapy has been realized by this technology. Bifunctional chelating agents for several radionuclides useful for PET and SPECT imaging have also been prepared using click chemistry. This review concludes that click chemistry is not the perfect conjugation and assembly technology for all applications, but provides a powerful and attractive alternative to conventional chemistry. This chemistry has proven itself to be superior in satisfying many criteria (biocompatibility, selectivity, yield, stereospecificity, etc.); thus one can expect it will consequently become a more routine strategy in the near future for a wide range of applications.

On the cellular metabolism of the click chemistry probe 19-alkyne arachidonic acid

“…In order to produce LTB 4 and LTB 4 -alk for functional studies, HEK293 cells that were stably transfected to express 5-LOX and FLAP (36,37) were stimulated with A23187 in the presence of 40 M of AA or AA-alk, respectively. 5-LOX products were separated by RP-HPLC as described above, and the LTB 4 and LTB 4 -alk peaks were collected, dried, and resuspended in ethanol.…”

“…5-LOX products were separated by RP-HPLC as described above, and the LTB 4 and LTB 4 -alk peaks were collected, dried, and resuspended in ethanol. Control experiments were performed with nontransfected HEK293 cells that do not express 5-LOX and FLAP and do not produce 5-LOX products (36).…”

“…To measure the chemoattractant activity of LTB 4 and LTB 4 -alk, 200 µl of neutrophil suspension (2.5 × 10 6 cells/ml HBSS containing 1.6 mM CaCl 2 and 5% FBS) preincubated with 0.3 U/ml adenosine deaminase were transferred to cell culture inserts (3.0 µm pore size; Falcon). Neutrophils were allowed to migrate (2 h, 37°C, 5% CO 2 ) to the lower chamber containing 700 µl HBSS/1.6 mM CaCl 2 along with 10 nM of LTB 4 -alk, LTB 4 , or diluent as negative control.…”

“…Neutrophils were allowed to migrate (2 h, 37°C, 5% CO 2 ) to the lower chamber containing 700 µl HBSS/1.6 mM CaCl 2 along with 10 nM of LTB 4 -alk, LTB 4 , or diluent as negative control. Inserts were then discarded, and cells that had migrated to the lower chamber were counted using the MOXI Z Mini automated cell counter (Orflo Technologies, Ketchum, ID).…”

Supramolecular metallogels for application in catalysis

“…62 A close examination of nature's favourite molecules, reveals a preference for making carbon-heteroatom bonds over carbon-carbon bonds. 63 For example, proteins are formed from amino acid building blocks joined by amide links. This carbon-heteroatom approach is in good agreement with the principles of "click" philosophy.…”