The use of bionanostructures in real-world applications will require precise control over biomolecular self-assembly and the ability to scale up production of these materials. A significant challenge is to control the formation of large, homogeneous arrays of bionanostructures on macroscopic surfaces. Previously, bionanostructure formation has been based on the spontaneous growth of heterogenic populations in bulk solution. Here, we demonstrate the self-assembly of large arrays of aromatic peptide nanotubes using vapour deposition methods. This approach allows the length and density of the nanotubes to be fine-tuned by carefully controlling the supply of the building blocks from the gas phase. Furthermore, we show that the nanotube arrays can be used to develop high-surface-area electrodes for energy storage applications, highly hydrophobic self-cleaning surfaces and microfluidic chips.
The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility and structural complexity, but they lack the precise base pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide backbone. All 16 combinations of the very short di-PNA building blocks were synthesized and assayed for their ability to self-associate. Only three guanine-containing di-PNAs-CG, GC and GG-could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The X-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base pairing. The assemblies were also found to exhibit optical properties including voltage-dependent electroluminescence and wide-range excitation-dependent fluorescence in the visible region.
Hyaluronic acid (HA), a major component of the extracellular matrix, is an attractive material for various medical applications. Yet, its low mechanical rigidity and fast in vivo degradation hinder its utilization. Here, we demonstrate the reinforcement of HA by its integration with a low-molecular-weight peptide hydrogelator to produce a composite hydrogel. The formulation of HA with the fluorenylmethoxycarbonyl diphenylalanine (FmocFF) peptide, one of the most studied self-assembling hydrogel-forming building blocks, showing notable mechanical properties, resulted in the formation of stable, homogeneous hydrogels. Electron microscopy analysis demonstrated a uniform distribution of the two matrices in the composite forms. The composite hydrogels showed improved mechanical properties and stability to enzymatic degradation while maintaining their biocompatibility. Moreover, the storage modulus of the FmocFF/HA composite hydrogels reached up to 25 kPa. The composite hydrogels allowed sustained release of curcumin, a hydrophobic polyphenol showing antioxidant, anti-inflammatory, and antitumor activities. Importantly, the rate of curcumin release was modulated as a function of the concentration of the FmocFF peptide within the hydrogel matrix. This work provides a new approach for conferring mechanical rigidity and stability to HA without the need of cross-linking, thus potentially facilitating its utilization in different clinical applications, such as sustained drug release.
The development of tools for the early diagnosis of pancreatic adenocarcinoma is an urgent need in order to increase treatment success rate and reduce patient mortality. Here, we present a modular nanosystem platform integrating soft nanoparticles with a targeting peptide and an active imaging agent for diagnostics. Biocompatible single-chain polymer nanoparticles (SCPNs) based on poly(methacrylic acid) were prepared and functionalized with the somatostatin analogue PTR86 as the targeting moiety, since somatostatin receptors are overexpressed in pancreatic cancer. The gamma emitter Ga was incorporated by chelation and allowed in vivo investigation of the pharmacokinetic properties of the nanoparticles using single photon emission computerized tomography (SPECT). The resulting engineered nanosystem was tested in a xenograph mouse model of human pancreatic adenocarcinoma. Imaging results demonstrate that accumulation of targeted SCPNs in the tumor is higher than that observed for nontargeted nanoparticles due to improved retention in this tissue.
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