Recent advance in solid state nanopores modification and characterization

Nanopore, due to its advantages of modifiable, controllability and sensitivity, has made a splash in recent years in the fields of biomolecular sequencing, small molecule detection, salt differential power generation, and biomimetic ion channels, etc. In these applications, the role of chemical or biological modification is indispensable. Compared with small molecules, the modification of polymers is more difficult and the methods are more diverse. Choosing appropriate modification method directly determines the success or not of the research, therefore, it is necessary to summarize the polymer modification methods toward nanopores. In addition, it is also important to provide clear and convincing evidence that the nanopore modification is successful, the corresponding characterization methods are also indispensable. Therefore, this review will summarize the methods of polymer modification of nanopores and efficient characterization methods. And we hope that this review will provide some reference value for like-minded researchers.

Shaping Soft Structures Using Bottom-up Layer-by-layer Assembly Technology for Biomedical Applications

Layer-by-layer (LbL) assembly is an easier, inexpensive, and highly versatile bottom-up methodology to modify surfaces and fabricate functional multilayer thin films and nanocomposites with fine-tuned compositions, structures, properties, and functions at the nanoscale. Since the early stages of its development, LbL technology has gathered increasing attention across different fields of application, including in the biomedical field owing to its mild processing conditions. In this chapter, we review the multitude of templates, spanning from the zero-dimensional to the three-dimensional, for shaping a diverse set of multifunctional soft-based LbL structures aiming for biomedical applications. Several examples are given on multilayered structures, including nano-to-macro particles and hollow capsules or tubes, multilayered thin films and free-standing membranes, multi-compartmentalized systems, porous scaffolds, and even dynamic living cell platforms, which can act as unprecedented building blocks to create highly complex LbL devices. We envisage that such a multitude of functional LbL devices will stimulate scientists to pursue the further development of LbL technology and foster its effective translation to practical biomedical applications.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Engineering nanolayered particles for modular drug delivery

Layer-by-layer (LbL) based self-assembly of nanoparticles is an emerging and powerful method to develop multifunctional and tissue responsive nanomedicines for a broad range of diseases. This unique assembly technique is able to confer a high degree of modularity, versatility, and compositional heterogeneity to nanoparticles via the sequential deposition of alternately charged polyelectrolytes onto a colloidal template. LbL assembly can provide added functionality by directly incorporating a range of functional materials within the multilayers including nucleic acids, synthetic polymers, polypeptides, polysaccharides, and functional proteins. These materials can be used to generate hierarchically complex, heterogeneous thin films on an extensive range of both traditional and novel nanoscale colloidal templates, providing the opportunity to engineer highly precise systems capable of performing the numerous tasks required for systemic drug delivery. In this review, we will discuss the recent advancements towards the development of LbL nanoparticles for drug delivery and diagnostic applications, with a special emphasis on the incorporation of biostability, active targeting, desirable drug release kinetics, and combination therapies into LbL nanomaterials. In addition to these topics, we will touch upon the next steps for the translation of these systems towards the clinic.

Molecular Assembly of Polysaccharide-Based Microcapsules and Their Biomedical Applications

Advanced multifunctional microcapsules have revealed great potential in biomedical applications owing to their tunable size, shape, surface properties, and stimuli responsiveness. Polysaccharides are one of the most acceptable biomaterials for biomedical applications because of their outstanding virtues such as biocompatibility, biodegradability, and low toxicity. Many efforts have been devoted to investigating novel molecular design and efficient building blocks for polysaccharide-based microcapsules. In this Personal Account, we first summarize the common features of polysaccharides and the main principles of the design and fabrication of polysaccharide-based microcapsules, and further discuss their applications in biomedical areas and perspectives for future research.

Cellulose-Rich Nanofiber-Based Functional Nanoarchitectures

Surface self-assembly of functional molecules or nanoscale building blocks is an effective strategy for the syntheses of advanced materials. Natural cellulose-rich substances have unique macro-to-nano hierarchical structural features. The fabrication of nanoarchitectures, employing specific guest species on the surfaces of the fine structures of such substances, results in corresponding artificial nanomaterials that possess the chemical functionalities and physical properties of both sides. Metal oxide thin film coatings with nanometer precision on the nanofibers of bulk cellulose-rich substances not only yield replicas of nanostructured materials, but also make it possible for further assemblies of functional units on the surfaces. Hence, nanostructured metal oxides and further composites, as well as surface-functionalized cellulose-based composites are fabricated by employing cellulose-rich substances as templates or scaffolds. The three-dimensional cross-linked porous structures, with the high surface area of the resultant nanomaterials or composites, lead to superior performance when employed as photocatalysts, electrode materials, and sensing matrices, on which this report is focused.

Biodegradable protein-based rockets for drug transportation and light-triggered release

We describe a biodegradable, self-propelled bovine serum albumin/poly-l-lysine (PLL/BSA) multilayer rocket as a smart vehicle for efficient anticancer drug encapsulation/delivery to cancer cells and near-infrared light controlled release. The rockets were constructed by a template-assisted layer-by-layer assembly of the PLL/BSA layers, followed by incorporation of a heat-sensitive gelatin hydrogel containing gold nanoparticles, doxorubicin, and catalase. These rockets can rapidly deliver the doxorubicin to the targeted cancer cell with a speed of up to 68 μm/s, through a combination of biocatalytic bubble propulsion and magnetic guidance. The photothermal effect of the gold nanoparticles under NIR irradiation enable the phase transition of the gelatin hydrogel for rapid release of the loaded doxorubicin and efficient killing of the surrounding cancer cells. Such biodegradable and multifunctional protein-based microrockets provide a convenient and efficient platform for the rapid delivery and controlled release of therapeutic drugs.

Polymer melt flow through nanochannels: from theory and fabrication to application

This short review presents the theory, fabrication, and application of polymer melts through nanochannels.

An Escherichia coli trap in human serum albumin microtubes

Human serum albumin microtubes captured Escherichia coli (E. coli) into their one-dimensional pore space interior with a high efficiency. Similar MTs including an Fe₃O₄ layer also captured E. coli and were manipulated by a magnetic field.

Protein-based nanotubes for biomedical applications

This review presents highlights of our latest results of studies directed at developing protein-based smart nanotubes for biomedical applications. These practical biocylinders were prepared using an alternate layer-by-layer (LbL) assembly of protein and oppositely charged poly(amino acid) into a nanoporous polycarbonate (PC) membrane (pore diameter, 400 nm), with subsequent dissolution of the template. The tube wall typically comprises six layers of poly-L-arginine (PLA) and human serum albumin (HSA) [(PLA/HSA)(3)]. The obtained (PLA/HSA)(3) nanotubes (NTs) can be dispersed in aqueous medium and are hydrated significantly. Several ligands for HSA, such as zinc(II) protoporphyrin IX (ZnPP), were bound to the HSA component in the cylindrical wall. Similar NTs comprising recombinant HSA mutant, which has a strong binding affinity for ZnPP, captured the ligand more tightly. The Fe(3)O(4)-coated NTs can be collected easily by exposure to a magnetic field. The hybrid NTs bearing a single avidin layer as an internal wall captured biotin-labeled nanoparticles into the central channel when their particle size is sufficiently small to enter the pores. The NTs with an antibody surface interior entrapped human hepatitis B virus with size selectivity. It is noteworthy that the infectious Dane particles were encapsulated completely into the hollows. Other HSA-based NTs having an α-glucosidase inner wall hydrolysed a glucopyranoside to yield α-D-glucose. A perspective of the practical use of the protein-based NTs is also described.

Unconventional layer-by-layer assembly: surface molecular imprinting and its applications

Layer-by-layer assembly (LbL) is a rich, versatile, and powerful technique for fabricating multilayer thin films with controlled architecture and functions. Singly charged, uncharged, or water-repellent molecules cannot be used directly in conventional LbL assembly. This problem can be solved with unconventional LbL methods, by employing the preassembly of building blocks in solution and the use of these assemblies for LbL formation at the interface. This Concept summarizes different methods of unconventional LbL assembly, including electrostatic complex formation, hydrogen-bonded complexes, block-copolymer micelles, and π-π interaction complexes. These preassembly treatments endow the building blocks with enhanced abilities for advanced functionality, in particular, surface molecular imprinting, a new concept emerging from unconventional LbL. Molecular imprinting approaches are thus conceptually described based on different types of interactions and their great potential in applications is demonstrated by examples such as selective surface patterning and selective filtration.

Layer-by-Layer Assemblies in Nanoporous Templates: Nano-Organized Design and Applications of Soft Nanotechnology

The synergistic combination of layer-by-layer (LbL) assembly and nanoporous membrane templating has greatly facilitated the creation of complex and functional nanotubular structures. The approach takes advantage of both the new properties conferred by assembling diverse LbL building blocks and the tight dimensional control offered by nanotemplating to enable new functionalities that arise from the highly anisotropic "one-dimensional" LbL-nanotube format. In this review, we aim to convey the key developments and provide a current snap-shot of such templated LbL nanoarchitectures. We survey recent developments that have enabled the assembly of polymers, biomolecules and inorganic nanoparticles "à la carte", via electrostatic, covalent and specific (bio)recognition interactions. We also discuss the emerging mechanistic understanding of the LbL assembly process within the nanopore environment. Finally, we present a diverse range of LbL nanotube "devices" to illustrate the versatility of the nanotemplated LbL toolbox for generating functional soft nanotechnology.

pH-responsive reversibly swellable nanotube arrays

We demonstrate a technique for synthesizing substrate-bound arrays of submicrometer-sized reversibly swellable tubes by using porous templates. The sacrificial template approach allows straightforward control over the tube length, diameter, and lateral arrangement of the resultant surface-bound nanotubes. We also explored methods for varying the tube opening structure by altering the pore shape at the surface of the template. A specific PEM system composed of poly(allylamine hydrochloride) and poly(acrylic acid) was chosen as the building block for the nanotube arrays because of its ability to undergo pH-triggered swelling-deswelling transitions. The activation of this transition results in dramatic changes in the length and diameter of the nanotubes as characterized in situ via confocal laser scanning microscopy (CLSM). The pH-driven reversible swelling-deswelling and nanoporosity behavior observed with planar films and nanotubes of this PEM system is a direct consequence of the breaking and reforming of ionic cross-links.

Hierarchic Nanostructure for Auto‐Modulation of Material Release: Mesoporous Nanocompartment Films

The preparation of mesoporous nanocompartment films composed of both hollow silica capsules and silica particles by using layer‐by‐layer (LbL) adsorption is described. The resultant nanocompartment films exhibit stepwise release of encapsulated water molecules without application of external stimuli. The hollow hierarchic pore structure of the silica capsules, including their internal void and mesoporous walls, is a key factor for the regulation and stepwise release of water, and is probably caused by the non‐equilibrated concurrent evaporation of material from the mesopore and capillary penetration into the mesopores. The number of release steps and rate of release can be tuned by variation of several parameters including water content, ambient temperature, layer multiplicity, and co‐adduct particle size. Application of the mesoporous nanocompartment films for the release of substances, including therapeutic agents and fragrances, indicates that the stepwise material release can be applied for a wide range of liquid substances. The films should lead to a novel material release system useful even for biomedical applications capable of controlled and sustained delivery of drug molecules.

Supramolecular approaches to biological therapy

Supramolecular chemistry is a useful methodology for construction of nano- or micro-sized objects and can significantly contribute to nanotechnology through so-called bottom-up processing. In addition, supramolecular self-assembled structures can mimic some aspects of biological systems. Bio-related functions such as molecular sensing, controlled release, signaling and materials separations have been realized. Supramolecular chemistry is a multidisciplinary field that includes subjects such as molecular design and nanosized materials. In this article recent examples of supramolecular chemistry in the context of biological therapy are introduced and classified into five categories: small supramolecular systems; designer polymers; self-assembled structures; predesigned assemblies; and nanomaterials. Finally, hierarchic organization of supramolecular structures for advanced functions is introduced to illustrate future directions of investigation. We hope that scientists studying therapeutic applications receive inspiration from this review to exploit the opportunities offered by supramolecular chemistry in their respective research areas.

Hydrothermal-induced structure transformation of polyelectrolyte multilayers: from nanotubes to capsules

The assembled polyelectrolyte nanotubes composed of poly(styrenesulfonate) and poly(allylamine hydrochloride) multilayers by using the layer-by-layer assembly combined with the porous template method can be transformed into capsules by a high-temperature treatment. Scanning electron microscopy and confocal laser scanning microscopy images revealed the whole transition process. The structure transformation of polyelectrolyte multilayers after annealing can be initiated by the input of thermal energy which leads to a breakage of ion pairs between oppositely charged polyelectrolyte groups. The transition process from tubes to capsules is supposed to be driven by the Raleigh instability and leads to the generated polyelectrolyte capsules with different sizes.