Multi-modal switching in responsive DNA block co-polymer conjugates

Abstract

New classes of information-rich DNA block co-polymer conjugates were synthesised, encoded with thermoresponsive and biocompatible poly(tri(ethylene glycol)ethyl ether methacrylate) (pTriEGMA) chains and oligomeric nucleic acids connected by either bioreducible or non-reducible links. The pTriEGMA chains were grown from initiator-functionalised hybridised DNA, designed to assemble with toehold overhangs. Functional information in the conjugates was explored via dynamic light scattering (DLS) and atomic force microscopy (AFM), in order to evaluate (i) reversible self-assembly into supramolecular structures across the pTriEGMA phase transition temperature; (ii) conformational change via addition of competing DNA sequences across the toeholds, and (iii) reductive cleavage of polymer-DNA links. The results showed that discrete nanoscale conjugates could reversibly associate through pTriEGMA phase behaviour and that size and association behaviour in one class of conjugate could be switched by addition of a competing DNA sequence and by reduction to break the polymer-DNA links. Preliminary experiments with the DNA-conjugates as delivery systems for doxorubicin to a cancer cell line indicated good tolerability of the conjugates alone and cytotoxic efficacy when loaded with the drug.

Controlling self‐assembly of DNA‐polymer conjugates for applications in imaging and drug delivery

“…DPC assembly is in large part driven by minimizing contact between the hydrophobic polymer regions and the aqueous solvent. Thus, thermoresponsive polymers such as PNIPAAm or poly[tri(ethylene glycol)ethyl ether methacrylate] (pTriEGMA) can be employed to control assembly as a function of temperature . Below a lower critical solution temperature (LCST), these polymers are water soluble; however, once the solution temperature is raised above the LCST, the polymers become hydrophobic, initiating assembly.…”

“…The two key requirements for these reactions are that they must be compatible with the relatively polar solvents required to dissolve DNA, and they must not use reagents that are damaging to the DNA or polymer. Among the most commonly utilized coupling reactions are copper-catalyzed azide-alkyne cycloaddition, 21 Michael addition, 22 disulfide bond formation, 18 and amide bond formation. 23 In some cases, additional reagents must be added to prevent polymer or DNA degradation.…”

“…Thus, thermoresponsive polymers such as PNIPAAm or poly[tri(ethylene glycol)ethyl ether methacrylate] (pTriEGMA) can be employed to control assembly as a function of temperature. 18,39,40 Below a lower critical solution temperature (LCST), these polymers are water soluble; however, once the solution temperature is raised above the LCST, the polymers become hydrophobic, initiating assembly. Maeda and coworkers found that for PNIPAAm-containing DPCs, both polymer size and structure influence assembly behavior.…”

“…Alexander and coworkers have reported DPCs composed of two complementary DNA strands that are each functionalized with pTriEGMA such that upon hybridization, there is one polymer attached to each end of the duplex (Figure 4). 18 These amphiphilic duplexes can assemble into micellar structures, and this assembly process can be directed using three different types of stimuli. First, due to the thermoresponsive nature of pTriEGMA, the micelles dissociate when the solution temperature is reduced below the LCST.…”

“…The most common method for generating DPCs involves separate synthesis of the DNA and polymer followed by solution‐phase conjugation (Figure (a)). The polymer can be synthesized using a variety of polymerization methods including ring‐opening metathesis polymerization (ROMP) or atom‐transfer radical‐polymerization (ATRP) to give linear or branched polymers. Depending upon the structure and properties desired, the composition of the polymer can be adjusted to tune hydrophobicity, which in turn modulates the assembly properties of the resulting DPCs .…”