Cationic Graft Copolymers as Carriers for Delivery of Antisense‐Oligonucleotides

Abstract

Self‐assembling systems based on ionic complexes of DNA fragments (36 base pairs), bcl‐2 antisense oligonucleotides (octadecamer), oligophosphates (25 phosphate groups) or acrylic oligomers (18 groups of phosphonic acid) with poly(L‐lysine) (PLL) ($\overline M _{\rm w}$ = 130 000 and 88 000) grafted with short poly[N‐(2‐hydroxypropyl)methacrylamide] (PHPMA) chains ($\overline M _{\rm n}$ = 4 300 or 8 600) were studied by static and dynamic light scattering methods as systems suitable for gene therapy applications. The graft copolymers (GPLLs) with shorter PHPMA grafts ($\overline M _{\rm n}$ = 4 300) provide polyelectrolyte complexes (PECs) with smaller $\overline M _{\rm w}$ and RH than the corresponding GPLLs with longer grafts ($\overline M _{\rm n}$ = 8 600) and the same content of PLL. The lowest aggregation number of 2 was observed for PECs prepared from the GPLL with short grafts and 40 wt.‐% of PLL. The complexes of oligonucleotides and DNA fragments with GPLLs showed quite similar behavior to that with oligophosphates and acrylic oligomer. The complexes prepared from GPLLs containing 40 wt.‐% of PLL and at excess of oligophosphate were stable for at least 48 h under physiological conditions (0.15 M NaCl) and in bovine serum albumin solutions (1 mg · mL−1). Additionally, polyanion exchange reactions of the PECs in contact with poly(styrenesulfonate) and DNA were studied in 0.15 M NaCl solutions. The oligophosphates in complexes were at least partially substituted with high‐molecular‐weight polyanions. The structure of the initial PECs dominated the PEC structure after the exchange reaction.The dependence of the molecular weight $\overline M _{\rm w}$ (a) and the hydrodynamic radius RH (b) of complexes of the oligophosphate (OPP) and four graft copolymers (GPLLi, i = 0–3) on the mixing ratio X.magnified imageThe dependence of the molecular weight $\overline M _{\rm w}$ (a) and the hydrodynamic radius RH (b) of complexes of the oligophosphate (OPP) and four graft copolymers (GPLLi, i = 0–3) on the mixing ratio X.

Complex coacervate core micelles

“…Typically, D-C3Ms exhibit lower critical ionic strengths, I cr , and aggregation numbers, P agg , and higher critical micellization concentrations (CMCs) than their S-C3Ms counterparts. With increasing copolymer block length ratio, N corona /N core , S-C3M molecular weight, M w , P agg , and hydrodynamic radius, R h are found to decrease [27,60,63,71,89,90,203,211,245]. For a given N corona , micellar size increases with increasing N core , [18,90,92,187,222] while for a given N core , R h increases with increasing N corona [118,119,125].…”

“…In the intracellular environment, one may envision exchange reactions with mRNA, sulphated sugars, and nuclear chromatin, while in the extracellular medium, one may think of exchange with blood serum proteins, such as BSA. Several studies found DNA-incorporation to be (at least partially) reversible as PAsp could replace DNA in DNA/PEO-b-PLys C3Ms [248], PSS could (at least partially) replace DNA from C3Ms of DNA/PHPMA-g-PLys, [71] and PVS could partially replace DNA from C3Ms of DNA/PEO-b-PLys [204]. Oupicky et al, found that while PSS could, albumin could not release DNA from DNA/PHPMA-b-PTMAEMA micelles in the presence of salt [207].…”

Characterization of Polyion Complex Micelles Designed to Address the Challenges of Oligonucleotide Delivery

“…Another reasonable explanation is that as more polymer is added to go from low N/P ratios to ratios closer to neutrality, the number of micelles increases, leading to higher scattering intensity. Alternatively, Dautzenberg et al have shown that the maximum in scattering intensity was associated with an increase in the mean polymer weight fraction of individual PICMs, reflecting an increase in the density or compactness of the micelles (37). It is therefore suggested that the increase in scattering intensity observed here at the N/P ratio of 1.5 is due to the combined effects of the number of micellar assemblies and of hydrophobicity on size and density of the micelles.…”

Hydrolytically and Reductively Degradable High‐Molecular‐Weight Poly(ethylene glycol)s

“…[20,21] Changes of c and n due to a surface coating of PECs were calculated by a procedure given in our previous papers. [22,23] We have determined the refractive index increment of polymer 14, n ¼ 0.138 mL Á g À1 . Since the structure of the coating polymer contains almost 90 wt.-% of PEG chains it is not surprising that this value is very close to that of neat PEG, n ¼ 0.135 mL Á g À1 .…”