Preparation of compact biocompatible quantum dots using multicoordinating molecular-scale ligands based on a zwitterionic hydrophilic motif and lipoic acid anchors

Abstract

Luminescent quantum dots (QDs) can potentially be used for many biological experiments, provided that they are constructed in such a way as to be stable in biological matrices. Furthermore, QDs that are compact in size and easy to couple to biomolecules can be readily used for applications ranging from protein tracking to vasculature imaging. In this protocol, we describe the preparation of ligands comprising either one or two lipoic acid (LA) groups chemically linked to a zwitterion moiety. These ligands are then used to functionalize luminescent QDs via a photochemical transformation of LA. This route produces nanocrystals that are compact in size and stable over a broad range of conditions. In addition, the resulting QDs are readily self-assembled with polyhistidine-appended proteins. This mode of conjugation maintains the protein biological activity and its orientation, yielding highly promising fluorescent conjugates that can be used for imaging and sensing. The protocol in its entirety can be completed in 3 weeks.

Electrostatic Repulsion Controls Efficiency of Cu‐Free Click‐Reaction with Azide‐Modified Semiconductor Quantum Dots

“…Application of colloidal semiconductor quantum dots (QDs) as luminescent markers in biotechnology relies on their narrow and controllable emission band, high photoluminescence (PL) quantum yield, possibility of excitation in a wide spectral range and excellent photostability. Nowadays, modern technology allows obtaining water‐soluble colloidal semiconductor QDs with a wide variety of functional groups on the surface . One of the most important steps for practical application of QDs is their controlled conjugation with various biomolecules .…”

“…Nowadays, modern technology allows obtaining water-soluble colloidal semiconductor QDs with a wide variety of functional groups on the surface. [1][2][3][4][5][6][7][8][9] One of the most important steps for practical application of QDs is their controlled conjugation with various biomolecules. [10][11][12][13] Unlike simple molecular systems, conjugation with colloidal nanoparticles possesses some specific features, which have to be taken into consideration when choosing conjugation methods.…”

The delivery of doxorubicin of multifunctional β‐cyclodextrin‐modified CdSe/ZnS quantum dots for bioactivity and nano‐probing

“…For the applications of QDs, some functionalized molecules modified on QDs surface are required to realize stability and to satisfy the requirements of the specific application . So several alternative coating bio‐ligands including peptides, amino acids, carbohydrates, and DNA can be interfaced, and the QD‐biocomposites have a wide range of applicability in many biological fields . For example, gadolinium‐doped iron oxide nanoparticle (GION) combining doxorubicin (Dox) and folic acid (FA) (FA‐GION‐Dox) could target drug delivery to monitor cancer treatment …”

“…[21,22] So several alternative coating bio-ligands including peptides, amino acids, carbohydrates, and DNA can be interfaced, and the QD-biocomposites have a wide range of applicability in many biological fields. [23][24][25] For example, gadolinium-doped iron oxide nanoparticle (GION) combining doxorubicin (Dox) and folic acid (FA) (FA-GION-Dox) could target drug delivery to monitor cancer treatment. [26] To date, various delivery platforms for chemotherapy agents have been developed to help diagnose and treat cancer.…”

Organic-to-Aqueous Phase Transfer of Cadmium Chalcogenide Quantum Dots Using a Sulfur-Free Ligand for Enhanced Photoluminescence and Oxidative Stability

“…Several effective methods of phase transfer have been devised 1, 16-21 , but the most common have serious drawbacks for photocatalysis and imaging. The most popular method for water-solubilization of metal-chalcogenide QDs is the exchange of the native ligands for ligands with a hydrophilic tail and thiolate anchoring group, such as mercaptopropionic (or - undecanoic) acid 9, 15 , glutathione 22 , thiotic acid 18, 23 and lipoic acid 20, 24 , or cysteine. 25 For CdSe QDs, thiolate ligands in certain binding geometries introduce mid-gap localized trap states and accompanying picosecond-timescale decay pathways for the exciton, and thereby reduce the yield of both photoluminescence (PL), important for imaging, and extraction of holes, important for catalysis.…”