Self-assembly of proteins and inorganic nanoparticles into terminal assemblies makes possible a large family of uniformly sized hybrid colloids. These particles can be compared in terms of utility, versatility and multifunctionality to other known types of terminal assemblies. They are simple to make and offer theoretical tools for designing their structure and function. To demonstrate such assemblies, we combine cadmium telluride nanoparticles with cytochrome C protein and observe spontaneous formation of spherical supraparticles with a narrow size distribution. Such self-limiting behaviour originates from the competition between electrostatic repulsion and non-covalent attractive interactions. Experimental variation of supraparticle diameters for several assembly conditions matches predictions obtained in simulations. Similar to micelles, supraparticles can incorporate other biological components as exemplified by incorporation of nitrate reductase. Tight packing of nanoscale components enables effective charge and exciton transport in supraparticles as demonstrated by enzymatic nitrate reduction initiated by light absorption in the nanoparticle.

Herein, we present a light‐gated protocell model made of plasmonic colloidal capsules (CCs) assembled with bacteriorhodopsin for converting solar energy into electrochemical gradients to drive the synthesis of energy‐storage molecules. This synthetic protocell incorporated an important intrinsic property of noble metal colloidal particles, namely, plasmonic resonance. In particular, the near‐field coupling between adjacent metal nanoparticles gave rise to strongly localized electric fields and resulted in a broad absorption in the whole visible spectra, which in turn promoted the flux of photons to bacteriorhodopsin and accelerated the proton pumping kinetics. The cell‐like potential of this design was further demonstrated by leveraging the outward pumped protons as “chemical signals” for triggering ATP biosynthesis in a coexistent synthetic protocell population. Hereby, we lay the ground work for the engineering of colloidal supraparticle‐based synthetic protocells with higher‐order functionalities.

Supraparticles are micelle-like self-limited assemblies from inorganic nanoparticles (NPs), whose size and morphology are determined by the equilibrium between short-range attraction and long-range repulsion forces. They can be spontaneously assembled from a variety of nanoscale components that are, in the majority of cases, the same NPs. Hybrid supraparticles made from inorganic and biological components are possible but hardly known. We report here the self-assembly of hybrid bioinorganic supraparticles, prepared from iron disulfide, cadmium telluride, and zinc oxide NPs as well as protease, cytochrome c, and formate dehydrogenase, in which the protein content can exceed that of NPs by 3:1. The resulting bioinorganic supraparticles are 70–150 nm in diameter and have a narrow size distribution. Five different permutations of inorganic and biological components indicate the generality of the observed phenomena. Coarse-grained molecular dynamics simulations confirmed that the formation of supraparticles depends on the interplay between attraction strengths and electrostatic repulsion. Enzymatic activity of the native protein is retained and is completely recovered from the assemblies, which suggests that the supraparticles can be utilized for encapsulation of biomolecules.

Figure 4. a) Schematic of synthetic protocellularcommunicationdriven ATPs ynthesis. b) ATPsynthesis under different conditions: (i)AuAgNR SPCs + proteoliposomes + light, (ii)AuAgNR SPCs + proteoliposomes in dark, (iii)proteoliposomes + light, (iv) AuNP SPCs + proteoliposomes + light, and (v) SiO 2 NP SPCs + proteoliposomes + light. c) Recycling of AuAgNR SPCs for communication with different batches of proteoliposomes for ATPsynthesis.

The purple membrane (PM) isolated from the bacteria Halobacterium salinarum (H. salinarum) arranges the transmembrane proton pump bacteriorhodopsin (bR) in a 2D hexagonal crystalline lattice. Here, PM sheets containing native bR bend into tube-like structures with open edges under acidic pH conditions. When decorated with gold nanoparticles (AuNPs), these same PM sheets yield a sealed tube assembly. Upon Rhodamine B (Rh B) sequestration inside the sealed tube, a dramatic decrease in Rh B fluorescence lifetime (τ f ) from 1.5 ns (unencapsulated) to 14 ps (encapsulated) is observed. The dramatic decrease in lifetime is attributed to energy transfer between AuNPs and Rh B. Subsequent release from the AuNP-PM capsules triggered by an increase in pH shows that 93% of Rh B is recovered (τ = 14 min) due to the capsules' unfolding. The hybrid AuNP-PM material highlights the utility of multicomponent ensembles (i.e., lipid bilayer, protein array, and NPs) by demonstrating that complex, multistimuli 3D responses can lead to multiplexed functions such as controlling energy transfer in the confined, encapsulated state and breaking the energy pair via molecular release in response to a change in pH.