Shear Effects on Stability of DNA Complexes in the Presence of Serum

Abstract

The behavior of nanocarriers, even though they are well-defined at equilibrium conditions, is unpredictable in living system. Using the complexes formed by plasmid DNA (pDNA) and K (K: lysine), protamine, or polylysine (PLL) as models, we studied the dynamic behavior of gene carriers in the presence of fetal bovine serum (FBS) and under different shear rates, a condition mimicking the internal physical environment of blood vessels. Without shear, all the positively charged complexes bind to the negatively charged proteins in FBS, leading to the formation of large aggregates and even precipitates. The behaviors are quite different under shear. The shear generates two effects: a mechanical force to break down the complex into smaller size particles above a critical shear rate and a stirring effect leading to secondary aggregation of complexes below the critical shear rate. In the studied shear rate from 100 to 3000 s, the mechanical force plays a key role in K/pDNA and protamine/pDNA, while the stirring effect is dominant in PLL/pDNA. A model study shows that the interfacial tension, the chain density, and the elasticity of the complexes determine their responsiveness to shear force. This study is helpful to understand the fate of drug/gene carriers under physiological conditions. It also gains insight in designing drug/gene carriers with desirable properties for in vivo applications.

Polymeric Delivery of Therapeutic Nucleic Acids

“…Liang et al further expanded on the effects of blood shear flow on PEGylated carriers by demonstrating that a denser incorporation of a PEG protective layer will withstand a higher shear flow before becoming perturbed and exposing the cationic core to serum proteins . A critical shear flow can be quantified via properties such as surface tension, PEG grafting density, and the elasticity, which agrees well with the work from Liang’s group . At low shear flows, the PEG is disturbed exposing the DNA/cationic core to protein, resulting in complex aggregation.…”

“…521 A critical shear flow can be quantified via properties such as surface tension, PEG grafting density, and the elasticity, which agrees well with the work from Liang's group. 522 At low shear flows, the PEG is disturbed exposing the DNA/cationic core to protein, resulting in complex aggregation. At higher flow rates, the force deforms the complexes into smaller sizes thus preventing further aggregation.…”

On Complex Coacervate Core Micelles: Structure-Function Perspectives

“…Neutral-cationic block copolymers generally yield relatively stable C3Ms when mixed with polynucleotides; however, they may be dissociated if there are competitive charged species in solution such as endogenous RNA, glycosaminoglycans and negatively charged polysaccharides [ 40 ]. Additionally, shear forces inside the blood vessels can also break down C3Ms [ 41 ]. Colloidal stability is increased by intracellularly reversible crosslinking [ 42 , 43 , 44 ], the introduction of hydrophobic moieties in the block copolymer [ 45 , 46 , 47 , 48 ], covalent grafting of RNA to a polymer backbone [ 49 ], or oligomerization of the encapsulated polynucleotide chains to increase their molecular weight and thereby the cohesion of the C3M [ 50 , 51 ].…”