Although promising, it is challenging to develop a simple and universal method for the high-efficiency delivery of biomacromolecules into diverse cells. Here, a universal delivery platform based on gold nanoparticle layer (GNPL) surfaces is proposed. Upon laser irradiation, GNPL surfaces show such good photothermal properties that absorption of the laser energy causes a rapid increase in surface temperature, leading to enhanced membrane permeability of the cultured cells and the diffusion of macromolecules into the cytosol from the surrounding medium. The high-efficiency delivery of different macromolecules such as dextran and plasmid DNA into different cell types is achieved, including hard-to-transfect mouse embryonic fibroblasts (mEFs) and human umbilical vein endothelial cells (HUVECs), while cell viability is well maintained under optimized irradiation conditions. The platform vastly outperforms the leading commercial reagent, Lipofectamine 2000, especially in transfecting hard-to-transfect cell lines (plasmid transfection efficiency: ≈53% vs ≈19% for mEFs and ≈44% vs ≈8% for HUVECs). Importantly, as the gold nanoparticles (GNPs) constituting the GNPL are firmly immobilized together, the potential cytotoxicity caused by endocytosis of GNPs is effectively avoided. This platform is reliable, efficient, and cost-effective with high-throughput and broad applicability across different cell types, opening up an innovative avenue for high-efficiency intracellular delivery.

For various human healthcare and industrial applications, endowing surfaces with the capability to not only efficiently kill bacteria but also release dead bacteria in a rapid and repeatable fashion is a promising but challenging effort. In this work, the synergistic effects of combining stimuli-responsive polymers and nanomaterials with unique topographies to achieve smart antibacterial surfaces with on-demand switchable functionalities are explored. Silicon nanowire arrays are modified with a pH-responsive polymer, poly(methacrylic acid), which serves as both a dynamic reservoir for the controllable loading and release of a natural antimicrobial lysozyme and a self-cleaning platform for the release of dead bacteria and the reloading of new lysozyme for repeatable applications. The functionality of the surface can be simply switched via step-wise modification of the environmental pH and can be effectively maintained after several kill–release cycles. These results offer a new methodology for the engineering of surfaces with switchable functionalities for a variety of practical applications in the biomedical and biotechnology fields.

Developing surfaces with antithrombotic properties is of great interest for the applications of blood-contacting biomaterials and medical devices. It is promising to coimmobilize two or more biomolecules with different and complementary functions to improve blood compatibility. However, the general one-pot strategy usually adopted by previous studies suffers the problems of inevitable competition between diverse biomolecules and uncontrollability of the relative quantities of the immobilized biomolecules. To solve these problems, a new sequential coimmobilization strategy is proposed and applied to fabricate a blood compatible surface. Polyurethane surface is modified with a copolymer, poly(2-hydroxyethyl methacrylate-co-1-adamantan-1-ylmethyl methacrylate), which serves as a linker-spacer for sequential attachment of two functional molecules, a hexapeptide containing REDV (Arg-Glu-Asp-Val) sequence, and a modified cyclodextrin bearing 7 lysine ligands, through covalent bonding and host–guest interaction, respectively. The resulting surface combines the antithrombogenic properties of the vascular endothelium and the clot lysing properties of the fibrinolytic system. Importantly, neither of the two functions of REDV peptide and lysine is compromised by the presence of the other, suggesting the enhanced blood compatibility. These results suggest a new strategy to engineer multifunctional surfaces by coimmobilization of bioactive molecules having unique functionalities.

A novel biomaterial based on polyurethane (PU) was prepared through physical incorporation of lysine-containing copolymer to improve its hemocompatibility and surface recognition of plasminogen. The lysine-containing copolymer was synthesized via the copolymerization of 2-ethylhexyl methacrylate (EHMA), oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and 6-tert-butoxycarbonyl amino-2-(2-methyl-acryloylamino)-hexanoic acid tert-butyl ester (Lys(P)MA), followed by the deprotection of COOH and ε-NH₂ groups on lysine residues in the copolymer. The composition of the copolymer can be adjusted by varying the monomer feed ratio. The three components contribute to improving the compatibility with PU, resistance to nonspecific protein adsorption and specific binding of plasminogen, respectively. The binding capacity towards plasminogen increased with the lysine content in the copolymer. This approach illustrates a simple way for the generation of novel biomaterials with improved hemocompatibility and surface recognition of specific biomolecules.

With the aim of improving the hemocompatibility of blood-contacting devices, antithrombotic or fibrinolytic biological molecules-containing polyurethane (PU) materials have been developed. Cationic PU surfaces were prepared by grafting poly(dimethylaminoethyl methacrylate) and quaternizing the tertiary amino groups with iodomethane. The surfaces were characterized by water contact angles and X-ray photoelectron spectroscopy. The materials (PU-CH₃I) were treated with antithrombotic or fibrinolytic drugs, such as hirudin or tissue plasminogen activator (tPA) in Tris-buffered saline (pH 9.0) to yield hirudin-loaded or tPA-loaded PU surfaces. The hirudin and tPA quantity of the surfaces was observed using a radiolabeling method. The quantities of hirudin and tPA taken up by the cationic surfaces were significantly greater than those on the unmodified PU: approximately 200-fold greater for hirudin and 10-fold for tPA. The release of the bound hirudin and tPA from the materials in contact with plasma was slow, and at 48 h, ~78% of the initial hirudin and ~26% of the initial tPA remained bound. The activity of the bound hirudin and tPA, as measured by a plasma recalcification assay, was largely preserved. This approach may have potential for the development of surfaces having antithrombotic or fibrinolytic properties. Copyright © 2011 John Wiley & Sons, Ltd.

Changes in the bioactivity of a protein after being adsorbed on a material surface may result from conformational changes of the protein. Unfortunately, however, direct evidence of such conformational changes of proteins adsorbed on a flat material surface is sparse so far. This is because probing the conformation of an adsorbed protein on material surfaces, especially flat ones, remains a challenge due to considerable experimental difficulties. In this study, the surface-enhanced Raman scattering (SERS) technique is used to characterize the conformational changes of a protein (lysozyme) adsorbed on tailored flat gold substrates with different chemistries. Two such substrates are formed by self-assembly of octadecanethiol and thiolated PEG on gold chips (Au-C18 and Au-PEG). Preliminary results reveal that, compared to the hydrophobic Au-C18 surface, the hydrophilic Au-PEG surface has much smaller effect on the conformation of lysozyme in aqueous solution, which thereby keeps its high bioactivity. The conformational changes of lysozyme adsorbed on material surfaces with different chemistries are well correlated with changes in its bioactivity.