Nonisocyanate Thermoplastic Polyhydroxyurethane Elastomers via Cyclic Carbonate Aminolysis: Critical Role of Hydroxyl Groups in Controlling Nanophase Separation.

Thermoplastic polyhydroxyurethanes (PHUs) were synthesized from cyclic carbonate aminolysis. Because of the hydroxyl groups in PHU, the choice of soft segment has a dramatic influence on nanophase separation in polyether-based PHUs. Use of a polyethylene glycol-based soft segment, which results in nanophase-separated thermoplastic polyurethane elastomers (TPUs), leads to single-phase PHUs that flow under the force of gravity. This PHU behavior is due to major phase mixing caused by hydrogen bonding of hard-segment hydroxyl groups to the soft-segment ether oxygen atoms. This hydrogen bonding can be suppressed by using polypropylene glycol-based or polytetramethylene oxide (PTMO)-based soft segments, which reduce hydrogen bonding by steric hindrance and dilution of oxygen atom content and result in nanophase-separated PHUs with robust, tunable mechanical properties. The PTMO-based PHUs exhibit reversible elastomeric response with hysteresis, like that of conventional TPUs. Because of nanophase separation with broad interphase regions possessing a wide range of local composition, the PTMO-based PHUs also demonstrate potential as novel broad-temperature-range acoustic and vibration damping materials, a function not observed with TPUs.

Temperature driven assembly of like-charged nanoparticles at non-planar liquid-liquid or gel-air interfaces.

Gold nanoparticles (NPs) functionalized with 2-fluoro-4-mercaptophenol (FMP) ligands form densely packed NP films at liquid-liquid interfaces, including surfaces of liquid droplets. The process is driven by a gradual lowering of temperature that changes the solution's pH, altering both the energy of interfacial adsorption for NPs traveling from solution to the interface as well as the balance between electrostatic and vdW interactions between these particles. Remarkably, the system shows hysteresis in the sense that the films remain stable when the temperature is increased back to the initial value. The same phenomena apply to gel-air interfaces, enabling patterning of these wet materials with durable NP films.

Branched disulfide-based polyamidoamines capable of mediating high gene transfection.

DNA condensation, endosomal escape of DNA/polymeric complexes, and unpacking of DNA are the key steps in the process of non-viral gene delivery. Amongst these steps, currently the unpacking of the DNA cargo from the DNA/polymeric nanocomplexes is the most challenging and arguably the most crucial if one wants to achieve high gene transfection with minimum cytotoxicity in the target cell. In this report we review current and past examples in the literature that demonstrate concerted efforts in designing and synthesizing various forms of cationic polymeric vectors having "built in" features. Such features can be certain types of chemical functional groups, such as amines and acids or other degradable bonds like esters, carbonates and disulfides, which allow for breakdown of polymeric vectors in certain cellular compartments. This may lead the DNA cargo to dissociate from the DNA/polymer complexes so as to maximize intracellular gene delivery. Furthermore, we provide further evidence that it is possible to achieve the goal of high gene transfection coupled with low cytotoxicity via rational design and formulation of branched polyamidoamines containing disulfide bonds. The DNA binding ability of these polymers and particle size as well as zeta potential of their DNA complexes were investigated. The cytotoxicity of pure polymer and polymer/DNA complexes at various polymer concentrations was studied in HEK293 human embryonic kidney, HepG2 human liver carcinoma, 4T1 mouse breast cancer and HeLa human cervical cancer cell lines. In vitro gene transfection efficiency induced by polymer/DNA complexes was explored in these cell lines by using luciferase and GFP reporter genes in comparison with PEI.

Brush-Like Amphoteric Poly[isobutylene-alt-(maleic acid)-graft-oligoethyleneamine)]/DNA Complexes for Efficient Gene Transfection.

Synthetic gene delivery vectors, especially cationic polymers have attracted enormous attention in recent decades because of their ease of manufacture, targettability, and scaling up. However, certain issues such as high cytotoxicity and low transfection efficiency problems have hampered the advance of nonviral gene delivery. In this study, we designed and synthesized brush-like amphoteric poly[isobutylene-alt-(maleic acid)-graft-oligoethyleneamine] capable of mediating highly efficient gene transfection. The polymers are composed of multiple pendant oligoethyleneimine molecules with alternating carboxylic acid moiety grafted onto poly[isobutylene-alt-(maleic anhydride)]. The polymer formed from pentaethylenehexamine {i.e., poly[isobutylene-alt-(maleic acid)-graft-pentaethylenehexamine)]} was able to condense DNA efficiently into nanoparticles of size around 200 nm with positive zeta potential of about 28-30 mV despite its amphoteric nature. Luciferase expression level and percentage of GFP expressing cells induced by this polymer was higher than those mediated with polyethyleneimine (branched, $\overline M _{\rm w} $ 25 kDa) by at least one order of magnitude at their optimal N/P ratios on HEK293, HepG2, and 4T1 cells. In vitro cytotoxicity testing revealed that the polymer/DNA complexes were less cytotoxic than those of PEI, and the viability of the cells after being incubated with the polymer/DNA complexes at the optimal N/P ratios was higher than 85%. This polymer can be a promising gene delivery carrier for gene therapy.