Inspired by the simplicity and versatility of layer-by-layer (LbL) assembly, we apply multilayered polyelectrolyte assemblies on nanoparticles to create viable systemic delivery systems. Focusing on tumor specific delivery, LbL nanoparticles that exhibit a pH sensitive outer stealth layer are demonstrated to target and be retained in hypoxic tumor regions. The neutral layers shed in response to acidity to reveal a charged nanoparticle surface that is readily taken up by tumor cells. The first in vivo demonstration of this mechanism of targeting is presented, as well as an initial examination of mechanism of uptake of the nanoparticles. We further demonstrate that this concept for tumor targeting is potentially valid for a broad range of cancers, with applicability for therapies that target hypoxic tumor tissue.

The effects of protein surface potential on the self-assembly of protein-polymer block copolymers are investigated in globular proteins with controlled shape through two approaches: comparison of self-assembly of mCherry-poly(N-isopropylacrylamide) (PNIPAM) bioconjugates with structurally homologous enhanced green fluorescent protein (EGFP)-PNIPAM bioconjugates, and mutants of mCherry with altered electrostatic patchiness. Despite large changes in amino acid sequence, the temperature-concentration phase diagrams of EGFP-PNIPAM and mCherry-PNIPAM conjugates have similar phase transition concentrations. Both materials form identical phases at two different coil fractions below the PNIPAM thermal transition temperature and in the bulk. However, at temperatures above the thermoresponsive transition, mCherry conjugates form hexagonal phases at high concentrations while EGFP conjugates form a disordered micellar phase. At lower concentration, mCherry shows a two-phase region while EGFP forms homogeneous disordered micellar structures, reflecting the effect of changes in micellar stability. Conjugates of four mCherry variants with changes to their electrostatic surface patchiness also showed minimal change in phase behavior, suggesting that surface patchiness has only a small effect on the self-assembly process. Measurements of protein/polymer miscibility, second virial coefficients, and zeta potential show that these coarse-grained interactions are similar between mCherry and EGFP, indicating that coarse-grained interactions largely capture the relevant physics for soluble, monomeric globular protein-polymer conjugate self-assembly.

Changing polymer chemistry in protein–polymer conjugate block copolymers results in the formation of previously unobserved cubic phases and changes in protein–polymer interactions that create large shifts in phase transitions, providing a powerful tool for nanostructure control.

Perfectly defi ned, monodisperse fusion protein block copolymers of a thermoresponsive coil-like protein, ELP, and a globular protein, mCherry, are demonstrated to act as fully biosynthetic analogues to protein-polymer conjugates that can self-assemble into biofunctional nanostructures such as hexagonal and lamellar phases in concentrated solutions. The phase behavior of two mCherry-ELP fusions, E 10 -mCherry-E 10 and E 20 -mCherry, is investigated to compare linear and bola fusion self-assembly both in diluted and concentrated aqueous solution. In dilute solution, the molecular topology impacts the stability of micelles formed above the thermal transition temperature of the ELP block, with the diblock forming micelles and the bola forming unstable aggregates. Despite the chemical similarity of the two protein blocks, the materials order into block copolymer-like nanostructures across a wide range of concentrations at 30 wt% and above, with the bola fusion having a lower order-disorder transition concentration than the diblock fusion. The topology of the molecule has a large impact on the type of nanostructure formed, with the two fusions forming phases in the opposite order as a function of temperature and concentration. This new system provides a rich landscape to explore the capabilities of fusion architecture to control supramolecular assemblies for bioactive materials.

Selective deuteration is an important tool for many analytical techniques including neutron scattering and spectroscopies. However, the availability of deuterated materials is limited because of the challenges in their synthesis. Here, we report the synthesis of partially and fully deuterated ε-caprolactone monomers and their corresponding polymers, poly(ε-caprolactone)s (PCLs), and the investigation of isotope effects on their crystalline structures and physical properties. Deuteration of PCLs leads to smaller crystal lattices and volumes compared to protiated PCLs by the amount proportional to the deuteration levels. The linear trend suggests that the volume isotope effect in PCL is primarily governed by the vibrations of C−D and C−H bonds. The large intrachain contraction of deuterated PCLs compared to that of polyethylene reported in the literature can be ascribed to the presence of polar ester groups in PCLs. Deuterated PCLs also display lower melting temperatures than protiated PCLs proportional to their deuteration levels because of weaker intermolecular interactions in deuterated polymers. FTIR spectroscopy, with support from density functional theory calculations, shows large red shifts of the stretching and bending frequencies of C−D versus C−H bonds as dictated by their relative reduced masses 13/7 , and to a smaller degree for the CO stretching frequency. This work is among the very few studies comparing the effects of partial versus full deuteration on the structures and properties in semicrystalline polymers. These results not only advance our understanding of isotope effects in polymeric materials but also provide an important avenue to design polymers with desirable properties.