DNA-Directed Assembly of a Cell-Responsive Biohybrid Interface for Cargo Release

Charge controlled interactions between DNA-modified silica nanoparticles and fluorosurfactants in microfluidic water-in-oil droplets

Microfluidic droplets are an important tool for studying and mimicking biological systems, e.g., to examine with high throughput the interaction of biomolecular components and the functionality of natural cells, or to develop basic principles for the engineering of artificial cells. Of particular importance is the approach to generate a biomimetic membrane by supramolecular self-assembly of nanoparticle components dissolved in the aqueous phase of the droplets at the inner water/oil interface, which can serve both to mechanically reinforce the droplets and as an interaction surface for cells and other components. While this interfacial assembly driven by electrostatic interaction of surfactants is quite well developed for water/mineral oil (W/MO) systems, no approaches have yet been described to exploit this principle for water/fluorocarbon oil (W/FO) emulsion droplets. Since W/FO systems exhibit not only better compartmentalization but also gas solubility properties, which is particularly crucial for live cell encapsulation and cultivation, we report here the investigation of charged fluorosurfactants for the self-assembly of DNA-modified silica nanoparticles (SiNP-DNA) at the interface of microfluidic W/FO emulsions. To this end, an efficient multicomponent Ugi reaction was used to synthesize the novel fluorosurfactant M4SURF to study the segregation and accumulation of negatively charged SiNP-DNA at the inner interface of microfluidic droplets. Comparative measurements were performed with the negatively charged fluorosurfactant KRYTOX, which can also induce SiNP-DNA segregation in the presence of cations. The segregation dynamics is characterized and preliminary results of cell encapsulation in the SiNP-DNA functionalized droplets are shown.

Dispersion Performances of Naphthalimides Doped in Dual Temperature- and pH-Sensitive Poly (N-Isopropylacrylamide-co-acrylic Acid) Shell Assembled with Vinyl-Modified Mesoporous SiO2 Core for Fluorescence Cell Imaging

Developing effective intelligent nanocarriers is highly desirable for fluorescence imaging and therapeutic applications but remains challenging. Using a vinyl-grafted BMMs (bimodal mesoporous SiO₂ materials) as a core and PAN ((2-aminoethyl)-6-(dimethylamino)-1H-benzo[de]isoquinoline-1,3(2H)-dione))-dispersed dual pH/thermal-sensitive poly(N-isopropylacrylamide-co-acrylic acid) as a shell, PAN@BMMs with strong fluorescence and good dispersibility were prepared. Their mesoporous features and physicochemical properties were extensively characterized via XRD patterns, N₂ adsorption-desorption analysis, SEM/TEM images, TGA profiles, and FT-IR spectra. In particular, their mass fractal dimension (d_m) features based on SAXS patterns combined with fluorescence spectra were successfully obtained to evaluate the uniformity of the fluorescence dispersions, showing that the d_m values increased from 2.49 to 2.70 with an increase of the AN-additive amount from 0.05 to 1%, along with the red shifting of their fluorescent emission wavelength from 471 to 488 nm. The composite (PAN@BMMs-I-0.1) presented a densification trend and a slight decrease in peak (490 nm) intensity during the shrinking process. Its fluorescent decay profiles confirmed two fluorescence lifetimes of 3.59 and 10.62 ns. The low cytotoxicity obtained via in vitro cell survival assay and the efficient green imaging performed via HeLa cell internalization suggested that the smart PAN@BMM composites are potential carriers for in vivo imaging and therapy.

Stable Immobilization of DNA to Silica Surfaces by Sequential Michael Addition Reactions Developed with Insights from Confocal Raman Microscopy

The immobilization of DNA to surfaces is required for numerous biosensing applications related to the capture of target DNA sequences, proteins, or small-molecule analytes from solution. For these applications to be successful, the chemistry of DNA immobilization should be efficient, reproducible, and stable and should allow the immobilized DNA to adopt a secondary structure required for association with its respective target molecule. To develop and characterize surface immobilization chemistry to meet this challenge, it is invaluable to have a quantitative, surface-sensitive method that can report the interfacial chemistry at each step, while also being capable of determining the structure, stability, and activity of the tethered DNA product. In this work, we develop a method to immobilize DNA to silica, glass, or other oxide surfaces by carrying out the reactions in porous silica particles. Due to the high specific surface area of porous silica, the local concentrations of surface-immobilized molecules within the particle are sufficiently high that interfacial chemistry can be monitored at each step of the process with confocal Raman microscopy, providing a unique capability to assess the molecular composition, structure, yield, and surface coverage of these reactions. We employ this methodology to investigate the steps for immobilizing thiolated-DNA to thiol-modified silica surfaces through sequential Michael addition reactions with the cross-linker 1,4-phenylene-bismaleimide. A key advantage of employing a phenyl-bismaleimide over a comparable alkyl coupling reagent is the efficient conversion of the initial phenyl-thiosuccinimide to a more stable succinamic acid thioether linkage. This transformation was confirmed by in situ Raman spectroscopy measurements, and the resulting succinamic acid thioether product exhibited greater than 95% retention of surface-immobilized DNA after 12 days at room temperature in aqueous buffer. Confocal Raman microscopy was also used to assess the conformational freedom of surface-immobilized DNA by comparing the structure of a 23-mer DNA hairpin sequence under duplex-forming and unfolding conditions. We find that the immobilized DNA hairpin can undergo reversible intramolecular duplex formation based on the changes in frequencies and intensities of the phosphate backbone and base-specific vibrational modes that are informative of the hybridization state of DNA.

Biofunctional Nanodot Arrays in Living Cells Uncover Synergistic Co-Condensation of Wnt Signalodroplets

Qualitative and quantitative analysis of transient signaling platforms in the plasma membrane has remained a key experimental challenge. Here, biofunctional nanodot arrays (bNDAs) are developed to spatially control dimerization and clustering of cell surface receptors at the nanoscale. High-contrast bNDAs with spot diameters of ≈300 nm are obtained by capillary nanostamping of bovine serum albumin bioconjugates, which are subsequently biofunctionalized by reaction with tandem anti-green fluorescence protein (GFP) clamp fusions. Spatially controlled assembly of active Wnt signalosomes is achieved at the nanoscale in the plasma membrane of live cells by capturing the co-receptor Lrp6 into bNDAs via an extracellular GFP tag. Strikingly, co-recruitment is observed of co-receptor Frizzled-8 as well as the cytosolic scaffold proteins Axin-1 and Disheveled-2 into Lrp6 nanodots in the absence of ligand. Density variation and the high dynamics of effector proteins uncover highly cooperative liquid-liquid phase separation (LLPS)-driven assembly of Wnt "signalodroplets" at the plasma membrane, pinpointing the synergistic effects of LLPS for Wnt signaling amplification. These insights highlight the potential of bNDAs for systematically interrogating nanoscale signaling platforms and condensation at the plasma membrane of live cells.

Cardiomyocyte-targeted anti-inflammatory nanotherapeutics against myocardial ischemia reperfusion (IR) injury

Myocardial ischemia reperfusion (IR) injury is closely related to the overwhelming inflammation in the myocardium. Herein, cardiomyocyte-targeted nanotherapeutics were developed for the reactive oxygen species (ROS)-ultrasensitive co-delivery of dexamethasone (Dex) and RAGE small interfering RNA (siRAGE) to attenuate myocardial inflammation. PPTP, a ROS-degradable polycation based on PGE₂-modified, PEGylated, ditellurium-crosslinked polyethylenimine (PEI) was developed to surface-decorate the Dex-encapsulated mesoporous silica nanoparticles (MSNs), which simultaneously condensed siRAGE and gated the MSNs to prevent the Dex pre-leakage. Upon intravenous injection to IR-injured rats, the nanotherapeutics could be efficiently transported into the inflamed cardiomyocytes via PGE₂-assisted recognition of over-expressed E-series of prostaglandin (EP) receptors on the cell membranes. Intracellularly, the over-produced ROS degraded PPTP into small segments, promoting the release of siRAGE and Dex to mediate effective RAGE silencing (72%) and cooperative antiinflammatory effect. As a consequence, the nanotherapeutics notably suppressed the myocardial fibrosis and apoptosis, ultimately recovering the systolic function. Therefore, the current nanotherapeutics represent an effective example for the co-delivery and on-demand release of nucleic acid and chemodrug payloads, and might find promising utilities toward the synergistic management of myocardial inflammation.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (experimental methods, RNA and primer sequences, ¹H NMR spectra, FTIR spectrum, TEM images, zeta potential, drug loading content, RNA and drug release, cytotoxicity, etc.) is available in the online version of this article at 10.1007/s12274-022-4553-6.