Macromolecular self-assembly (MSA) has been an active and fruitful research field since the 1980s, especially in this new century, which is promoted by the remarkable developments in controlled radical polymerization in polymer chemistry, etc. and driven by the demands in bio-related investigations and applications. In this review, we try to summarize the trends and recent progress in MSA in relation to biomimetic chemistry and bio-inspired materials. Our paper covers representative achievements in the fabrication of artificial building blocks for life, cell-inspired biomimetic materials, and macromolecular assemblies mimicking the functions of natural materials and their applications. It is true that the current status of the deliberately designed and obtained nano-objects based on MSA including a variety of micelles, multicompartment vesicles, and some hybrid and complex nano-objects is at their very first stage to mimic nature, but significant and encouraging progress has been made in achieving a certain similarity in morphologies or properties to that of natural ones. Such achievements also demonstrate that MSA has played an important and irreplaceable role in the grand and long-standing research of biomimetic and bio-inspired materials, the future success of which depends on mutual and persistent efforts in polymer science, material science, supramolecular chemistry, and biology.

Protein crystalline frameworks are attractive for biomimetic and nanotechnological studies because they could augment the useful functionalities of numerous proteins through dense packing and uniform orientation. However, their formation and precise structural control is challenging. Here we present novel protein crystalline frameworks with controllable interpenetration. The homotetrameric lectin concanavalin A is crosslinked by predetermined inducing ligands containing monosaccharide and rhodamine groups connected by an oligo(ethylene oxide) spacer. Two non-covalent interactions, that is, sugar-lectin binding and the dimerization of RhB, are responsible for the framework formation. The three-dimensional structure of the framework is fully characterized by X-ray crystallographic methods. For the first time, either interpenetrating or non-interpenetrating frameworks are obtained, and they are controlled by the spacer length of the inducing ligand. Further kinetics and mechanistic investigations reveal that, in the self-assembly process, the carbohydrate-protein binding occurs first, followed by RhB dimerization. This sequence favours rapid crystallization with a high yield when an excess amount of inducing ligand is used. In short, by using wellcontrolled dual non-covalent interactions, fast and versatile preparation of protein crystalline framework was achieved with high crystallization ratio of the proteins, which may shed light on protein crystallization in near future.

The enhancement effect of nucleation in immiscible blend systems has recently attracted interest. Although several authors have reported that the effect occurs at the phase interface, little is known about the mechanism involved. We focused on poly(L-lactide) (PLLA)/poly(ɛ-caprolactone) (PCL) immiscible blend systems in which the presence of PCL enhanced the nucleation of PLLA at low temperature. We investigated the nucleation behavior of PLLA during aging at temperatures below T g . Generally, neat polymers, including PLLA, seldom generate nuclei below T g due to restrictions in chain mobility. However, through DSC analysis of the crystallization behavior following an aging process, we revealed that the nucleation of PLLA occurs during aging even at temperatures below T g in the PLLA/PCL blend. Since the nuclei density became saturated with increasing aging time, the nucleation behavior was regarded as heterogeneous nucleation. The asymptotic density of nuclei depended on the PCL content, indicating that dispersed PCL acted as active sites for nucleation. The nucleation rate R was almost independent of the aging temperature, suggesting that the marked decrease in chain mobility due to the glass transition is locally evaded at the active sites. Nucleation was observed even at temperatures as much as 40 °C lower than T g following the addition of only 1 wt % PCL, while the T g obtained by a DSC heating scan showed a subtle decrease. This suggests that the limited miscibility of PLLA/PCL leads to the aggregation of PCL and induces local and deep depression of T g at the interface of the PCL domains, resulting in marked enhancement of PLLA nucleation.

Protein microtubule is a significant self-assembled architecture found in nature with crucial biological functions. However, mimicking protein microtubules with precise structure and controllable self-assembly behavior remains highly challenging. In this work, we demonstrate that by using dual supramolecular interactions from a series of well-designed ligands, i.e., protein-sugar interaction and π-π stacking, highly homogeneous protein microtubes were achieved from tetrameric soybean agglutinin without any chemical or biological modification. Using combined cryo-EM single-particle reconstruction and computational modeling, the accurate structure of protein microtube was determined. The helical protein microtube is consisted of three protofilaments, each of which features an array of soybean agglutinin tetramer linked by the designed ligands. Notably, the microtubes resemble the natural microtubules in their structural and dynamic features such as the shape and diameter and the controllable and reversible assembly behavior, among others. Furthermore, the protein microtubes showed an ability to enhance immune response, demonstrating its great potential for biological applications.

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Progressive Macromolecular Self-Assembly: From Biomimetic Chemistry to Bio-Inspired Materials -[219 refs.]. -(ZHAO, Y.; SAKAI, F.; SU, L.; LIU, Y.; WEI, K.; CHEN*, G.; JIANG, M.; Adv. Mater. (Weinheim, Ger.) 25 (2013) 37, 5215-5256, http://dx.