Toward Fluorescence‐Based High‐Throughput Screening for Enantiomeric Excess in Amines and Amino Acid Derivatives

A highly accurate and reliable screening method for enantiomeric excess of amine derivatives in the presence of water is reported. The fluorescence‐based screening system has been realized by self‐assembly of chiral diol‐type dyes (BINOL, VANOL and VAPOL), 2‐formylphenylboronic acid, and chiral amines forming iminoboronate esters. The structure and chirality of the amine analytes determine the stability of the diastereomeric iminoboronate esters, which in turn display differential fluorescence. The fluorescence signal reflects the enantiomeric purity of the chiral amines and was utilized in high‐throughput arrays. The arrays were able to recognize enantiomeric excess of amines, amino esters, and amino alcohols. In addition to qualitative analysis, quantitative experiments were successfully performed. Studies of the role of additives such as water or citrate were carried out to gain insight into the stability of the iminoboronate esters. It is shown that the above additives destabilize less stable esters while the stable esters remain unchanged. Thus, the presence of water and citrate leads to increased difference between the diastereomeric iminoboronates and contributes to the enantiodiscrimination of the chiral amines.     

Enzyme‐Responsive Multifunctional Magnetic Nanoparticles for Tumor Intracellular Drug Delivery and Imaging

Enzyme‐responsive, hybrid, magnetic silica nanoparticles have been employed for multifunctional applications in selective drug delivery and intracellular tumor imaging. In this study, doxorubicin (Dox)‐conjugated, enzyme‐cleavable peptide precursors were covalently tethered onto the surface of uniform silica‐coated magnetic nanoparticles through click chemistry. This enzyme‐responsive nanoparticle conjugate demonstrated highly efficient Dox release upon specific enzyme interactions in vitro. It also exhibits multiple functions in selective tumor intracellular drug delivery and imaging in the tumor cells with high cathepsin B expression, whereas it exhibited lower cytotoxicity towards other cells without enzyme expression.     

Supramolecular Self‐Assembly of Histidine‐Capped‐Dialkoxy‐Anthracene: A Visible‐Light‐Triggered Platform for Facile siRNA Delivery

Supramolecular self‐assembly of histidine‐capped‐dialkoxy‐anthracene (HDA) results in the formation of light‐responsive nanostructures. Single‐crystal X‐ray diffraction analysis of HDA shows two types of hydrogen bonding. The first hydrogen bond is established between the imidazole moieties while the second involves the oxygen atom of one amide group and the hydrogen atom of a second amide group. When protonated in acidic aqueous media, HDA successfully complexes siRNA yielding spherical nanostructures. This biocompatible platform controllably delivers siRNA with high efficacy upon visible‐light irradiation leading up to 90 % of gene silencing in live cells.     

Cross‐Platform Comparison of Therapeutic Delivery from Multilamellar Lipid‐Coated Polymer Nanoparticles

Significant efforts have been invested in finding a delivery system that can encapsulate and deliver therapeutics. Core–shell polymer‐lipid hybrid nanoparticles have been studied as a promising platform because of their mechanical stability, narrow size distribution, biocompatibility, and ability to co‐deliver diverse drugs. Here, novel core–shell nanoparticles based on a poly(lactic‐co‐glycolic acid) (PLGA) core and multilamellar lipid shell are designed, where the lipid bilayers are crosslinked between the two adjacent bilayers (PLGA‐ICMVs). The cross‐platform performance of the nanoparticles to other polymer‐lipid hybrid platforms is examined, including physicochemical characteristics, ability to encapsulate a variety of therapeutics, biocompatibility, and functionality as a vaccine delivery platform. Differential abilities of nanoparticle systems to encapsulate distinct pharmaceutics are observed, which suggest careful consideration of the platform chosen depending on the therapeutic agent and desired function. The novel PLGA‐ICMV platform herein demonstrates great potential in stably encapsulating water‐soluble agents and therefore is an attractive platform for therapeutic delivery.     

All‐in‐One Target‐Cell‐Specific Magnetic Nanoparticles for Simultaneous Molecular Imaging and siRNA Delivery

Cancer‐cell‐targeted gene silencing was observed with a magnetic‐nanoparticle platform (MEIO, magnetism‐engineered iron oxide) on which a fluorescent dye, siRNA, and a RGD‐peptide targeting moiety were attached (see picture). The different functionalities enable the macroscopic (magnetic resonance) and microscopic (fluorescence) imaging of target cells. This system may be suitable for concurrent diagnostic and therapeutic applications.

     

Polyethyleneimine‐Coated Gold Nanoparticles: Straightforward Preparation of Efficient DNA Delivery Nanocarriers

A novel one‐pot method for the synthesis of polyethyleneimine (PEI)‐coated gold nanoparticles (AuPEI‐NPs) that combines the reductant–stabilizer properties of PEI with microwave irradiation starting from hydrogen tetrachloroaurate acid (HAuCl₄) and branched PEI 25 kDa (b25kPEI) was explored. The method was straightforward, green, and low costing, for which the Au/PEI ratio (1:1 to 1:128 w/w) was a key parameter to modulate their capabilities as DNA delivery nanocarriers. Transfection assays in CHO‐k1 cells demonstrated that AuPEI‐NPs with 1:16 and 1:32 w/w ratios behaved as effective DNA gene vectors with improved transfection efficiencies (twofold) and significantly lower toxicity than unmodified b25kPEI and Lipofectamine 2000. The transfection mediated by these AuPEI‐NP–DNA polyplexes preferentially used the caveolae‐mediated route for intracellular internalization, as shown by studies performed by using specific internalization inhibitors as well as colocalization with markers of clathrin‐ and caveolae‐dependent pathways. The AuPEI‐NP polyplexes preferentially used the more efficient caveolae internalization pathway to promote transfection, a fact that supports their higher transfection efficiency relative to that of Lipofectamine 2000. In addition, intracellular trafficking of the AuPEI‐NPs was studied by transmission electron microscopy.     

Mesoporous‐Silica‐Functionalized Nanoparticles for Drug Delivery

The ever‐growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therapy.     

Calix[4]arene‐Functionalised Silver Nanoparticles as Hosts for Pyridinium‐Loaded Gold Nanoparticles as Guests

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1‐dodecanethiol and 1‐(11‐mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω‐alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X‐ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au‐AgNPs aggregation, shown through the low‐energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol‐capped AuNPs and the Ag calix[4]arene‐functionalised NPs was also promoted by the action of a simple N‐octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol‐capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs.     

Growth and Origami Folding of DNA on Nanoparticles for High‐Efficiency Molecular Transport in Cellular Imaging and Drug Delivery

A novel three‐dimensional (3D) superstructure based on the growth and origami folding of DNA on gold nanoparticles (AuNPs) was developed. The 3D superstructure contains a nanoparticle core and dozens of two‐dimensional DNA belts folded from long single‐stranded DNAs grown in situ on the nanoparticle by rolling circle amplification (RCA). We designed two mechanisms to achieve the loading of molecules onto the 3D superstructures. In one mechanism, ligands bound to target molecules are merged into the growing DNA during the RCA process (merging mechanism). In the other mechanism, target molecules are intercalated into the double‐stranded DNAs produced by origami folding (intercalating mechanism). We demonstrated that the as‐fabricated 3D superstructures have a high molecule‐loading capacity and that they enable the high‐efficiency transport of signal reporters and drugs for cellular imaging and drug delivery, respectively.     

High‐Throughput Synthesis and Screening of Combinatorial Heterogeneous Catalyst Libraries

In less than one minute the catalytic activity and selectivity of a single catalyst was measured in combinatorial libraries of ternary Rh‐Pd‐Pt‐Cu alloys. Only slightly more than two hours were needed to complete a library with 136 elements. The elements of the libraries (ca. 2–4 μg of material) are contained in a two‐dimensional array synthesized by a thin‐film technique. The analysis was performed by a scanning mass spectrometer (see picture).     

Bis‐clickable Mesoporous Silica Nanoparticles: Straightforward Preparation of Light‐Actuated Nanomachines for Controlled Drug Delivery with Active Targeting

Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co‐condensation of TEOS with variable amounts (2–5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on‐demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans‐to‐cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on‐command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin‐loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not.     

Photothermal Detection of Individual Gold Nanoparticles: Perspectives for High‐Throughput Screening

We use photothermal microscopy to detect and image individual gold nanoparticles that are either embedded in a polymer film or immobilized in an aqueous environment. Reducing the numerical aperture of the detection optics allows us to achieve a 200‐fold‐enlarged detection volume while still retaining sufficient detectivity. We characterize the capabilities of this approach for the detection of gold colloids with a diameter of 20 nm, with emphasis on practical aspects that are important for high‐throughput‐screening applications. The extended detection volume in combination with the stability of the photothermal signal are major advantages compared to fluorescence‐based approaches, which are limited by photoblinking and photobleaching. Careful consideration is given to the trade‐off between the maximum increase in local temperature that can be tolerated by a biological specimen and the minimum integration time needed to reliably determine whether a given volume contains a target species. We find that our approach has the potential to increase the detection‐limited flow rate (i.e. the limit given by the detection volume divided by the minimum detection time) by two to three orders of magnitude.     

Self‐Assembled Fluorescent Organic Nanoparticles for Live‐Cell Imaging

Fluorescent, cell‐permeable, organic nanoparticles based on self‐assembled π‐conjugated oligomers with high absorption cross‐sections and high quantum yields have been developed. The nanoparticles are generated with a tuneable density of amino groups for charge‐mediated cellular uptake by a straightforward self‐assembly protocol, which allows for control over size and toxicity. The results show that a single amino group per ten oligomers is sufficient to achieve cellular uptake. The non‐toxic nanoparticles are suitable for both one‐ and two‐photon cellular imaging and flow cytometry, and undergo very efficient cellular uptake.     

Primary Ammonium Monocarboxylate Synthon in Designing Supramolecular Gels: A New Series of Chiral Low‐Molecular‐Weight Gelators Derived from Simple Organic Salts that are Capable of Generating and Stabilizing Gold Nanoparticles

The primary ammonium monocarboxylate (PAM) synthon has been exploited to generate a new series of PAM salts from the free amine of L ‐phenylalanine‐3‐pyridyl amide, (S)‐2‐amino‐3‐phenyl‐N‐(pyridine‐3‐yl)propanamine (designated as “ B ”), and various substituted benzoic acids (designated as “ A(R) ”; R =4‐Me, 4‐Cl, 4‐Br, 4‐NO₂, 3‐Me, 3‐Cl, 3‐Br, 3‐NO₂, 2‐Me, 2‐Cl, 2‐Br, 2‐NO₂). The 4‐ and 3‐substituted benzoate salts showed moderate‐to‐excellent gelation ability with a number of polar and apolar solvents. The gels were characterized by DSC, rheology, SEM and TEM, FTIR spectroscopy, etc. Structure–property studies based on single‐crystal powder X‐ray diffraction (PXRD) and FTIR data provided insights into the role of the PAM synthon in the formation of the gel networks. Interestingly, some of the gels were capable of forming and stabilizing gold nanoparticles at room temperature without the use of any exogenous reducing agents.     

Mesenchymal‐Mode Migration Assay and Antimetastatic Drug Screening with High‐Throughput Microfluidic Channel Networks

Increasing evidence shows that activated mesenchymal migration is a key process of the metastatic cascade. Cancer cells usually gain such migratory capability through an epithelial‐to‐mesenchymal transition. Herein we present a high‐throughput microfluidic device with 3120 microchambers to specifically monitor mesenchymal migration. Through imaging of the whole chip and statistical analysis, we can evaluate the two key factors of velocity and percentage related to cell migratory capacity at different cell densities in culture. We also used the device to screen antimetastatic drugs for their inhibition of mesenchymal migration and prevention of metastatic malignancy. This device will provide an excellent platform for biologists to gain a better understanding of cancer metastasis.