Nano-thin walled micro-compartments from transmembrane protein–polymer conjugates

Abstract

The high interfacial activity of protein-polymer conjugates has inspired their use as stabilizers for Pickering emulsions, resulting in many interesting applications such as synthesis of templated micro-compartments and protocells or vehicles for drug and gene delivery. In this study we report, for the first time, the stabilization of Pickering emulsions with conjugates of a genetically modified transmembrane protein, ferric hydroxamate uptake protein component A (FhuA). The lysine residues of FhuA with open pore (FhuA ΔCVF) were modified to attach an initiator and consequently controlled radical polymerization (CRP) carried out via the grafting-from technique. The resulting conjugates of FhuA ΔCVF with poly(N-isopropylacrylamide) (PNIPAAm) and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA), the so-called building blocks based on transmembrane proteins (BBTP), have been shown to engender larger structures. The properties such as pH-responsivity, temperature-responsivity and interfacial activity of the BBTP were analyzed using UV-Vis spectrophotometry and pendant drop tensiometry. The BBTP were then utilized for the synthesis of highly stable Pickering emulsions, which could remain non-coalesced for well over a month. A new UV-crosslinkable monomer was synthesized and copolymerized with NIPAAm from the protein. The emulsion droplets, upon crosslinking of polymer chains, yielded micro-compartments. Fluorescence microscopy proved that these compartments are of micrometer scale, while cryo-scanning electron microscopy and scanning force microscopy analysis yielded a thickness in the range of 11.1 ± 0.6 to 38.0 ± 18.2 nm for the stabilizing layer of the conjugates. Such micro-compartments would prove to be beneficial in drug delivery applications, owing to the possibility of using the channel of the transmembrane protein as a gate and the smart polymer chains as trigger switches to tune the behavior of the capsules.

Enzyme–Polymer Conjugates as Robust Pickering Interfacial Biocatalysts for Efficient Biotransformations and One‐Pot Cascade Reactions

“…In this context, it has been well-known for decades that conjugating polymers to proteins can enhance protein solubility and stability in an on-natural environment, [11] while achieving sufficient interfacial capability to stabilize PEs. [12] Ther esulting emulsions can be used as biological building blocks to construct sophisticated structures for applications such as protocell mimics [13] and self-assembled membranes. [14] However,t here has been few reports yet on using these emulsions for as ynthetic purpose,d espite their potential as acarrier-free PIB system, possibly because of concerns about protein deactivation at the liquid-liquid interface and/or by the conjugation process.…”

Protein Nanopore Membranes Prepared by a Simple Langmuir–Schaefer Approach

“…Due to its pronounced amphiphilicity, FhuA has a strong tendency to assemble at interfaces, as we have demonstrated before with tensiometry measurements. [34] In this study, FhuA molecules were spread at the air-water interface of a Langmuir trough (Figure 1b(i)). Upon compression with the two movable barriers of the Langmuir trough, a dense 2D film was formed and stabilized by glutaraldehyde crosslinking.…”

“…[28][29][30][31][32] Using naturally pore-forming TPs instead of ferritin, we synthesized TP-polymer conjugates, [33] which were transformed into stable membranes by assembly at Pickering emulsion interfaces and subsequent UV crosslinking of the polymer chains. [34] Here, we present a straightforward method for the integration of functional TPs into planar ultrathin membranes. This strategy is based on the Langmuir technique and the homobifunctional crosslinker glutaraldehyde, being an efficient protein crosslinker and known not to impact the protein conformation in many cases.…”

Research progress in stimulus-responsive behaviors of artificial cells

“…蛋 白质囊泡的显著特点在于其模拟的细胞膜是由蛋白质 组分富集而成, 因此可以采用功能化蛋白构建蛋白质 囊泡, 获得具有目标功能的人工细胞. Charan等人 [30] 用跨膜蛋白通道作为物质进出的"门", 并将具有刺激 响应性的共轭聚合物接枝到跨膜蛋白上, 制备了具有 通透性可调节的蛋白质囊泡.…”