Cellular uptake: lessons from supramolecular organic chemistry

Abstract

The objective of this Feature Article is to reflect on the importance of established and emerging principles of supramolecular organic chemistry to address one of the most persistent problems in life sciences. The main topic is dynamic covalent chemistry on cell surfaces, particularly disulfide exchange for thiol-mediated uptake. Examples of boronate and hydrazone exchange are added for contrast, comparison and completion. Of equal importance are the discussions of proximity effects in polyions and counterion hopping, and more recent highlights on ring tension and ion pair-π interactions. These lessons from supramolecular organic chemistry apply to cell-penetrating peptides, particularly the origin of "arginine magic" and the "pyrenebutyrate trick," and the currently emerging complementary "disulfide magic" with cell-penetrating poly(disulfide)s. They further extend to the voltage gating of neuronal potassium channels, gene transfection, and the delivery of siRNA. The collected examples illustrate that the input from conceptually innovative chemistry is essential to address the true challenges in biology beyond incremental progress and random screening.

Intracellular Delivery of Native Proteins Facilitated by Cell‐Penetrating Poly(disulfide)s

“…[14][15][16][17][18] Thep ositively charged guanidinium groups in CPDs help cargo accumulation near the negatively charged mammalian cell surface and their disulfide backbone helps intracellular cargo delivery via disulfide-exchange mechanisms with no apparent endosomal trapping. [19] In the cytoplasm, CPDs undergo rapid depolymerization (< 5min), ap rocess catalyzed by endogenous glutathione (GSH). At present, both non-covalent and covalent conjugations are available to append CPDs to proteins modified either genetically or chemically with suitable "tags" (i.e.h istidine tag).…”

Rational Design of Nanocarriers for Intracellular Protein Delivery

“…Cell-Penetrating Poly(disulfide)s: The structures of cell-penetrating poly(disulfide)s (CPDs) is similar as polyarginine except the polypeptides backbone is replaced with poly(disulfide)s. [66,67] The CPDs were initially developed by Matile's group in 2013, which could be grown directly on the substrates by surfaceinitiated ring-opening disulfide-exchange polymerization method. [68,69] The polymer size could be adjusted by changing the polymerization time, initiator and monomer concentration.…”

“…Four of recombinant proteins including avidin, trans-cyclooctyne-BSA (TCO-BSA), TCO-anti-rabbit immunoglobulin G (IgG) and BRD-4, either covalently or noncovalently conjugated with CPDs were successfully delivered into different mammalian cells via endocytosis-independent pathways. [67] Copyright 2015, Royal Society of Chemistry. Moreover, to avoid genetical or chemical modification of proteins which might affect their activities, recently, the same group reported two complementary CPD-facilitated approaches (post-translation modification (PTM)-based tagging and traceless tagging) for delivery of "native" proteins ( Figure 3b).…”

Tuning the Properties of Penetrating Peptides by Oxime Conjugation

“…18 The formation of dynamic bonds constitutes a powerful strategy for the preparation of amphiphilic membrane transporters. 14,[19][20][21][22][23] Dynamic bonds such as hydrazones, oximes and disulfides offer two fundamental advantages for the synthesis of membrane carriers. [24][25][26][27][28] First, there is a synthetic advantage, because certain dynamic bonds (i.e.…”

“…Additionally, the final internalization pathway of a given peptide is often promiscuous and depends on different parameters such as concentration, nature of the cargo and size of the corresponding supramolecular aggregates. 10,12 Furthermore, the highly dynamic processes involved in membrane transport such as counterion exchange 13,14 and membrane partitioning, strongly hinder the acquisition of robust data and the development of predictive models. 6,15 Additionally, the conformational changes of the transported peptides are difficult to discern and to study in real time.…”