A Versatile Polymer‐Based Platform for Intracellular Delivery of Macromolecules

Abstract

The plasma membrane barrier greatly restricts intracellular delivery of macromolecules. Currently available methods suffer from various limitations, including low delivery efficiency, high cytotoxicity, or incompatibility with a wider range of macromolecules or cell types. To overcome these issues, stimuli‐responsive polymers such as the bio‐inspired, pH‐responsive poly(l‐lysine isophthalamide) grafted with l‐phenylalanine at a stoichiometric ratio of 50% (PP50) can be used. In mildly acidic environments, the pseudopeptidic polymer can permeabilize the plasma membrane overcoming the problem of payload entrapment in the endosomes and allowing for efficient intracellular delivery. It is demonstrated that PP50 is capable of intracellular delivery by simple co‐incubation at pH 6.5 with various macromolecules, including different‐sized Dextrans, green fluorescent protein (GFP), and an apoptotic peptide. The delivery process is fast, nontoxic, and compatible with multiple cell types, including adherent and suspension cell lines, primary human mesenchymal stem cells, and cells grown as spheroids. In addition, apoptotic peptide delivery by co‐incubation with PP50 is over three times more effective than delivery using other common methods, including poly(ethyleneimine) (PEI), cell penetrating peptides (CPPs), and electroporation. The findings suggest that payload delivery by co‐incubation with PP50 is a flexible, controllable method allowing delivery of various payloads to many different cell types in vitro.

Comb-like Pseudopeptides Enable Very Rapid and Efficient Intracellular Trehalose Delivery for Enhanced Cryopreservation of Erythrocytes

“…21 It has been reported that PP50 and hydrophilic dextran (polysaccharide of glucose) were present in a mixture with no obvious formation of complexes, suggesting limited interaction between the two components. 47 Similarly, PP50 would have limited interaction with hydrophilic trehalose (disaccharide of glucose), but it was argued that surrounding of PP50 by high concentrations of trehalose could inhibit its conformational change to hydrophobic compact polymer structures at mildly acidic pH, leading to inhibition of its membrane interaction and consequent reduction of trehalose loading and haemolysis. 21 Other researchers have reported similar observations on inhibition of peptide folding by high concentrations of trehalose, which can thickly cluster around constituent amino acids and shield them from each other.…”

Sustained Release Systems for Delivery of Therapeutic Peptide/Protein

“…Polymer is a kind of macromolecular compound synthesized through the addition or condensation polymerization of monomers with various reactive groups, which is now being widely applied in the exploitation and development of drug delivery systems owing to its good biocompatibility, ease of chemical modification, controllable molecular weight and structure, etc . − In the past decades, synthetic polymers such as poly­(lactic- co -glycolic acid) (PLGA) and polyethylene glycol (PEG) have been developed and approved by the FDA as long-acting formulations for delivery of protein/peptide therapeutics such as Adagen, Eligard, Bydureon, etc ., which are now vastly applied in the clinical treatment of various diseases such as severe combined immunodeficiency (SCID), cancer, and diabetes. − Natural polymers such as various kinds of polysaccharide are now being investigated extensively as carriers for loading biomacromolecules such as proteins attributed to their abundant sources, low price, and good biocompatibility and biodegradability, holding great potential in the future for resolving the issues previously mentioned. − …”

pH-Responsive Amphiphilic Carboxylate Polymers: Design and Potential for Endosomal Escape

“…Mechanistic insights suggest that phenylalanine modified PLP induced red blood cell membrane thinning of 35–40% normal thickness at endosomal pH, thus facilitating the transport of membrane-impermeable small molecular cargos (Lynch et al, 2011 ). Further real-time imaging showed that even large molecules such as FITC-labeled dextran of different molecular weights (10–500 kDa) and green fluorescence protein could be delivered to different mammalian cells after co-incubation with phenylalanine modified PLP at pH 6.5 (Kopytynski et al, 2020 ). Such a convenient and flexible method provides a versatile platform for cell engineering ex vivo .…”

“…(Wang, 2018;Evans et al, 2019). Albeit less renowned, recent studies show their emerging potentials for proteins, genes, and vaccine delivery (Mukalel et al, 2018;Qiu et al, 2018;Evans et al, 2019;Jacobson et al, 2019;Kopytynski et al, 2020).…”

“…Compared with polycationic polymeric carriers, anionic pH-responsive membrane permeabilizing polymers are less toxic, because of the repulsive charges against plasma membranes (Wang, 2018 ; Evans et al, 2019 ). Albeit less renowned, recent studies show their emerging potentials for proteins, genes, and vaccine delivery (Mukalel et al, 2018 ; Qiu et al, 2018 ; Evans et al, 2019 ; Jacobson et al, 2019 ; Kopytynski et al, 2020 ).…”