The properties of water on both molecular and macroscopic surfaces critically influence a wide range of physical behaviors, with applications spanning from membrane science to catalysis to protein engineering. Yet, our current understanding of water interfacing molecular and material surfaces is incomplete, in part because measurement of water structure and molecular-scale properties challenges even the most advanced experimental characterization techniques and computational approaches. This review highlights progress in the ongoing development of tools working to answer fundamental questions on the principles that govern the interactions between water and surfaces. One outstanding and critical question is what universal molecular signatures capture the hydrophobicity of different surfaces in an operationally meaningful way, since traditional macroscopic hydrophobicity measures like contact angles fail to capture even basic properties of molecular or extended surfaces with any heterogeneity at the nanometer length scale. Resolving this grand challenge will require close interactions between state-of-the-art experiments, simulations, and theory, spanning research groups and using agreed-upon model systems, to synthesize an integrated knowledge of solvation water structure, dynamics, and thermodynamics.

Osteoporosis is a degenerative bone disease commonly related to aging. With an increase in life expectancies worldwide, the prevalence of the disease is expected to rise. Current clinical therapeutic treatments are not able to offer long-term solutions to counter the bone mass loss and the increased risk of fractures, which are the primary characteristics of the disease. However, the combination of bioactive nanomaterials within a biomaterial scaffold shows promise for the development of a localized, long-term treatment for those affected by osteoporosis. This review summarizes the unique characteristics of engineered nanoparticles that render them applicable for bone regeneration and recaps the current body of knowledge on nanomaterials with potential for osteoporosis treatment and bone regeneration. Specifically, we highlight new developments that are shaping this emerging field and evaluate applications of recently developed nanomaterials for osteoporosis treatment. Finally, we will identify promising new research directions in nanotechnology for bone regeneration.

We introduce a powerful, widely applicable approach to characterizing polymer conformational distributions, specifically the end-to-end distance distributions, P(R ee ), accessed through double electron−electron resonance (DEER) spectroscopy in conjunction with molecular dynamics (MD) simulations. The technique is demonstrated on one of the most widely used synthetic, disordered, water-soluble polymers: poly(ethylene oxide) (PEO). Despite its widespread importance, no systematic experimental characterization of PEO's R ee conformational landscape exists. The evaluation of P(R ee ) is particularly important for short polymers or (bio)polymers with sequence complexities that deviate from simple polymer physics scaling laws valid for long chains. In this study, we characterize the R ee landscape by measuring P(R ee ) for low molecular weight (MW: 0.22−2.6 kDa) dilute PEO chains. We use DEER with end-conjugated spin probes to resolve R ee populations from ∼2−9 nm and compare them with full distributions from MD. The P( R ee )'s from DEER and MD show remarkably good agreement, particularly at longer chain lengths where populations in the DEER-unresolvable range (<1.5 nm) are low. Both the P(R ee ) and the root-mean-square R ̃ee indicate that aqueous PEO is a semiflexible polymer in a good solvent, with the latter scaling linearly with molecular weight up to its persistence length (l p ∼ 0.48 nm), and rapidly transitioning to excluded volume scaling above l p . The R ̃ee scaling is quantitatively consistent with that from experimental scattering data on high MW (>10 kDa) PEO and the P(R ee )'s crossover to the theoretical distribution for an excluded volume chain.

Surface modifying additives (SMAs), which may be readily blended into silicones to improve anti-fouling behavior, must have excellent surface migration potential and must not leach into the aqueous environment. In this work, we evaluated the efficacy of a series of poly(ethylene oxide) (PEO)-based SMA amphiphiles which varied in terms of crosslinkability, siloxane tether length (m) and diblock versus triblock architectures. Specifically, crosslinkable, diblock PEO-silane amphiphiles with two oligodimethylsiloxane (ODMS) tether lengths [(EtO)3Si-(CH2)3-ODMSm-PEO8, m = 13 and 30] were compared to analogous non-crosslinkable, diblock (H-Si-ODMSm-PEO8) and triblock (PEO8-ODMSm-PEO8) SMAs. Prior to water conditioning, while all modified silicone coatings exhibited a high degree of water-driven surface restructuring, that prepared with the non-crosslinkable diblock SMA (m = 13) was the most hydrophilic. After conditioning, all modified silicone coatings were similarly hydrophilic and remained highly protein resistant, with the exception of PEO8-ODMS30-PEO8. Notably, despite twice the PEO content, triblock SMAs were not superior to diblock SMAs. For diblock SMAs, it was shown that water uptake and leaching were also similar whether or not the SMA was crosslinkable.

The benefits of incorporating amphiphilic properties into antifouling and fouling-release coatings are well-established. The use of sequence-defined peptides and peptoids in these coatings allows precise control over the spacing and chemistry of the amphiphilic groups, but amphiphilic peptoids have generally outperformed analogous peptides for reasons attributed to differences in backbone structure. The present work demonstrates that the superior properties of peptoids relative to peptides are primarily attributable to a lack of hydrogen bond donors rather than to their secondary structure. A new amphiphilic peptoid was designed containing functional groups similar to those typically found on a hydrogen-bonding peptide backbone. This peptoid and a non-hydrogen-bonding peptoid analogue were incorporated as side chains in PDMS-based polymer scaffolds. Bioassays with the soft algal fouling organisms Ulva linza and Navicula incerta indicate that hydrogen bonding largely determines the differences seen between similar peptide and peptoid species, while sum frequency generation vibrational spectroscopy suggests that the presence of hydrogen bond donors enhances interfacial water structuring. This reduced initial U. linza adhesion, but attached algae were more strongly bound by hydrogen-bonding interactions. Consequently, amphiphilic peptoid materials lacking hydrogen bond donors are better suited to resist marine fouling, with enhanced release of U. linza and similar performance against N. incerta relative to hydrogen-bonding analogues.