Zwitterionic polymers exhibit excellent nonfouling performance due to their strong surface hydrations. However, salt molecules may severely reduce the surface hydrations of typical zwitterionic polymers, making the application of these polymers in real biological and marine environments challenging. Recently, a new zwitterionic polymer brush based on the protein stabilizer trimethylamine N-oxide (TMAO) was developed as an outstanding nonfouling material. Using surface-sensitive sum frequency generation (SFG) vibrational spectroscopy, we investigated the surface hydration of TMAO polymer brushes (pTMAO) and the effects of salts and proteins on such surface hydration. It was discovered that exposure to highly concentrated salt solutions such as seawater only moderately reduced surface hydration. This superior resistance to salt effects compared to other zwitterionic polymers is due to the shorter distance between the positively and negatively charged groups, thus a smaller dipole in pTMAO and strong hydration around TMAO zwitterion. This results in strong bonding interactions between the O– in pTMAO and water, and weaker interaction between O– and metal cations due to the strong repulsion from the N+ and hydration water. Computer simulations at quantum and atomistic scales were performed to support SFG analyses. In addition to the salt effect, it was discovered that exposure to proteins in seawater exerted minimal influence on the pTMAO surface hydration, indicating complete exclusion of protein attachment. The excellent nonfouling performance of pTMAO originates from its extremely strong surface hydration that exhibits effective resistance to disruptions induced by salts and proteins.

Recently, a super uranyl binding protein (SUP) was developed, which exhibits excellent sensitivity/selectivity to bind uranyl ions. It can be immobilized onto a surface in sensing devices to detect uranyl ions. Here, sum frequency generation (SFG) vibrational spectroscopy was applied to probe the interfacial structures of surface-immobilized SUP. The collected SFG spectra were compared to the calculated orientation-dependent SUP SFG spectra using a one-excitonic Hamiltonian approach based on the SUP crystal structures to deduce the most likely surface-immobilized SUP orientation(s). Furthermore, discrete molecular dynamics (DMD) simulation was applied to refine the surface-immobilized SUP conformations and orientations. The immobilized SUP structures calculated from DMD simulations confirmed the SUP orientations obtained from SFG data analyzed based on the crystal structures and were then used for a new round of SFG orientation analysis to more accurately determine the interfacial orientations and conformations of immobilized SUP before and after uranyl ion binding, providing an in-depth understanding of molecular interactions between SUP and the surface and the effect of uranyl ion binding on the SUP interfacial structures. We believe that the developed method of combining SFG measurements, DMD simulation, and Hamiltonian data analysis approach is widely applicable to study biomolecules at solid/liquid interfaces.

Albumin molecules are extensively used as biocompatible coatings, and poly(ethylene glycol) (PEG) materials are widely used for antifouling. PEG materials have excellent antifouling property because of their strong surface hydration. Our previous research indicates that hydration at the PEG/bovine serum albumin solution interface is stronger than that at the PEG/water interface. This research shows that this observation is general for different types of albumin molecules. Different albumins including bovine, porcine, rat, rabbit, and sheep serum albumins were studied in this research. It was found that the hydration at the PEG methacrylate (pOEGMA)/albumin solution interface is always stronger than that at the pOEGMA/water interface. Here, we define "strong interfacial hydration" as "ordered strongly hydrogen-bonded interfacial water". We believe that such a strong hydration is because of the strong hydration on the albumin surface, leading to its biocompatible property. All of the albumin molecules demonstrated stronger hydration on the pOEGMA surface compared to other protein molecules such as lysozyme and fibrinogen. The strong hydration on albumin molecules is related to the high surface coverage of glutamic acid and lysine with similar amounts.

emerging as an enabling technology. [1][2][3][4] The combination of flexibility and responsiveness allows applications in various fields, including wearable electronics, soft robotics, drug delivery, biomedical devices, and biomimetic design. [5][6][7][8][9][10] Among various material options, polymers play an essential role in fabricating flexible sensors and soft actuators due to their tailorability and the potential of integrating multiple functionalities, such as adaptive response to signals (e.g., chemical, mechanical, electrical), energy harvesting and storage, and biochemical sensing. [3,10] Adding responsive functionality to a polymer often involves methods such as copolymerizing monomers with different capability, attaching layers of active materials to a polymer matrix, building in molecular orientation or internal polarization, introducing structural heterogeneity by combining amorphous and crystalline domain or multi-layer assembly, and preparing composites by hybridizing organic and inorganic materials. [2,[11][12][13][14] Among various techniques, utilizing dynamic chemistry to enable polymer responsivity has received significant attention in the past few decades. [15,16] Reversible interactions, including dynamic covalent bonding, hydrogen bonding, ionic bonding, π-π stacking, and metal-ligand coordination, are susceptible to environmental variation and can achieve multiple physical and chemical responses via bond breaking and reforming. [17][18][19][20][21] Fascinating material properties arise from disrupting the equilibrium state of dynamic bonding, for example: polymers with spiropyran go through force-induced covalent-bond activation and give rise to visible color and fluorescence; supramolecular polymers containing metal-ligand motifs can self-heal by exposing to ultraviolet irradiation; and polymers functionalized by self-complementary hydrogen bonded ureidopyrimidinone (UPy) moieties shows shape-memory effect through temperature change. [22][23][24] Among these options, metal-ligand coordination bonding is particularly appealing to realize a particular desired response, because of the ease of tuning the stability of the bond.One of the most popular polymers for fabricating sensors and actuators is polydimethylsiloxane (PDMS). [2,7] It commonly serves as an essential substrate or a responsive component due to the attractive physical and chemical properties, including low Polymers are at the core of emerging flexible sensor and soft actuator technology. Ideal candidates not only respond to external stimuli but also have programmable response intensity and speed. Incorporating dynamic interactions into polymers has been widely studied. However, most research has focused on synthesis methods and on optical and mechanical effects of these interactions. Here, a new and tunable method of enabling environmentally adaptive polymers are introduced. Specifically, polar functionalities are "hidden" within polydimethylsiloxane (PDMS). When unveiled, these polar functionalities change the hydrophilicity ...

Protein structures at solid/liquid interfaces mediate interfacial protein functions, which are important for many applications. It is difficult to probe interfacial protein structures at buried solid/liquid interfaces in situ at...