DNA Strand Exchange Stimulated by Spontaneous Complex Formation with Cationic Comb-Type Copolymer

Cationic comb-type copolymers (CCCs) composed of a polycation backbone and water-soluble side chains accelerate by 4−5 orders the DNA strand exchange reaction (SER) between double helical DNA and its homologous single-strand DNA. The accelerating effect is considered due to alleviation of counterion association during transitional intermediate formation in sequential displacement pathway. CCCs stabilize not only matured hybrids but also the nucleation complex to accelerate hybridization

Photothermally Controllable Cytosolic Drug Delivery Based On Core–Shell MoS₂‑Porous Silica Nanoplates

Single-layered molybdenum sulfide (MoS₂) displays strong photothermal properties, but low colloidal stability in aqueous solution prevents its biomedical application as a functional drug delivery carrier. We report a photothermally controllable nanoplate consisting of porous silica-coated, single-layered MoS₂, modified with poly­(ethylene glycol) (PEG). Silica and PEG enhanced stability and maintained the single layer structure of MoS₂ for over a month. A representative anticancer drug, doxorubicin (DOX), was loaded into the silica structure and subsequent exposure to near-infrared irradiation facilitated both endosomal escape of the carrier and the release of DOX. DOX-loaded, silica-coated, single-layered MoS₂ (DOX–PSMS–PEG) showed better therapeutic effect against liver and colon cancer compared than free DOX did; a result probably attributable to the combined effects of photothermally facilitated endosomal escape and the vulnerability of cancer cells to localized heating. These studies suggest that considerable new opportunities may exist for spatiotemporally controllable drug delivery systems based on single-layered MoS₂

DNA Strand Exchange Stimulated by Spontaneous Complex Formation with Cationic Comb-Type Copolymer

Cationic comb-type copolymers (CCCs) composed of a polycation backbone and water-soluble side chains accelerate by 4−5 orders the DNA strand exchange reaction (SER) between double helical DNA and its homologous single-strand DNA. The accelerating effect is considered due to alleviation of counterion association during transitional intermediate formation in sequential displacement pathway. CCCs stabilize not only matured hybrids but also the nucleation complex to accelerate hybridization

Polymer–DNA Molecular Net for Selective Transportation of Target Biomolecules and Inhibition of Tumor Growth

We demonstrate a new concept of a molecular net for capturing, release, and transportation of target molecules by utilizing polymer-based DNA molecular net (PD-mn). Target biomolecules like DNA, ATP, and VEGF were successfully captured from a heterogeneous mixture of biomolecules and released by a stimulus without nonspecific degradation by PD-mn prepared by polymerization of acrylamide and acrydite-modified DNA. Furthermore, by introducing fluorescence-labeled competitor DNA, single-mismatched DNA was specifically detected. As a concept of artificial transporter, PD-mn selectively captured target biomolecules from a heterogeneous mixture of molecules into a specific enzymatic reaction solution and induced enzyme-mediated reaction. Finally, effective <i>in vivo</i> antitumor effect was demonstrated utilizing sheet-shaped PD-mn which has improved capture ability against VEGF as a target biomolecule by amplified DNA VEGF aptamer. This PD-mn could be used as not only a selective molecular adsorbent or artificial transporter for specific capture and release of target molecules but also therapeutics by specific capture of disease-related molecules

Tumor-Homing, Size-Tunable Clustered Nanoparticles for Anticancer Therapeutics

We present herein a pH-responsive dynamic DNA nanocluster based on gold nanoparticles with highly packed nucleic acid assembly and evaluate its potential as a drug delivery vehicle with tumor-specific accumulation. Each gold nanoparticle was readily functionalized with various functional DNA sequences; in particular, we modified the surface of gold nanoparticles with bcl-2 antisense and i-motif binding sequences. Clustering of the gold nanoparticles induced by hybridization of each DNA sequence <i>via</i> i-motif DNA provided tumor targeting and drug loading capabilities. After cellular uptake, the drug was released by disassembly of the gold nanoparticle cluster into single gold nanoparticles in response to the pH decrease in the late endosome. Furthermore, the antiapoptotic Bcl-2 protein was down-regulated by the antisense-modified gold nanoparticles; thus, drug-mediated apoptosis was significantly accelerated by sensitizing the cancer cells to the drug. Our size-tunable clustered nucleic acid-grafted gold nanoparticles provide tumor homing in the blood circulation and are thus a potential multifunctional therapeutic agent <i>in vivo</i> as well as <i>in vitro</i>

Photothermally Triggered Cytosolic Drug Delivery <i>via</i> Endosome Disruption Using a Functionalized Reduced Graphene Oxide

Graphene oxide has unique physiochemical properties, showing great potential in biomedical applications. In the present work, functionalized reduced graphene oxide (PEG-BPEI-rGO) has been developed as a nanotemplate for photothermally triggered cytosolic drug delivery by inducing endosomal disruption and subsequent drug release. PEG-BPEI-rGO has the ability to load a greater amount of doxorubicin (DOX) than unreduced PEG-BPEI-GO <i>via</i> π–π and hydrophobic interactions, showing high water stability. Loaded DOX could be efficiently released by glutathione (GSH) and the photothermal effect of irradiated near IR (NIR) in test tubes as well as in cells. Importantly, PEG-BPEI-rGO/DOX complex was found to escape from endosomes after cellular uptake by photothermally induced endosomal disruption and the proton sponge effect, followed by GSH-induced DOX release into the cytosol. Finally, it was concluded that a greater cancer cell death efficacy was observed in PEG-BPEI-rGO/DOX complex-treated cells with NIR irradiation than those with no irradiation. This study demonstrated the development of the potential of a PEG-BPEI-rGO nanocarrier by photothermally triggered cytosolic drug delivery <i>via</i> endosomal disruption

Synergistic Effect of Low Cytotoxic Linear Polyethylenimine and Multiarm Polyethylene Glycol: Study of Physicochemical Properties and <i>In Vitro</i> Gene Transfection

Novel star-shaped copolymers consisting of multiarm polyethylene glycol and low molecular weight linear polyethylenimines (MAPEG-LPEIs) with a high transfection efficiency and low cytotoxicity were designed and synthesized as nonviral gene delivery carriers. The cationic polymers were prepared by conjugating low molecular weight linear PEI (2.5 kDa) to six-arm PEG-NHS (10 kDa) in two different compositions. Two copolymers, MAPEG-LPEI3 and MAPEG-LPEI6 with molecular weights of 17.5 kDa and 25 kDa respectively, were synthesized. The MAPEG-LPEI3/pDNA and MAPEG-LPEI6/pDNA polyplexes are stably dispersed in aqueous media with a narrowly distributed size range of in vitro. MAPEG-LPEI6 exhibited higher transfection activity than that of MAPEG-LPEI3 at the same weight ratios. Furthermore, MAPEG-LPEI/pDNA polyplexes were less toxic than LPEI/pDNA complexes as determined by MTT assay. These favorable results could be attributed to the combined effect of low molecular weight LPEI and multiarm PEG. The special structural features of the multiarm star-shaped central PEG core play an important role in achieving higher transfection efficiency as it imparts higher charge density to polyplexes and prevents the unwanted aggregation of the smaller polyplex particles. These two important factors contributed toward enhanced gene transfection. On the other hand, LPEI provides low cytotoxicity and effective complexation with pDNA in the designed architecture. Therefore it is possible to achieve enhanced gene transfection by using these two components, namely, pivotal multiarm PEG core and LPEI, in optimal ratio as observed in the case of MAPEG-LPEI6.</sub

i‑Motif-Driven Au Nanomachines in Programmed siRNA Delivery for Gene-Silencing and Photothermal Ablation

The present work illustrates unique design, construction and operation of an i-motif-based DNA nanomachine templated on gold nanoparticles (AuNPs), which utilizes pH-responsive dynamic motion of i-motif DNA strands and aggregational behavior of AuNPs to elicit programmed delivery of therapeutic siRNA. The pH-sensitive nucleic acids immobilized on the AuNPs consisted of three functional segments, <i>i.e.</i>, an i-motif DNA, an overhanging linker DNA and a therapeutic siRNA. At neutral pH, the i-motif DNA is hybridized with the overhanging linker DNA segment of the therapeutic siRNA. However, in endosomal acidic pH, the i-motif DNA forms interstrand tetraplex, which could induce cluster formation of AuNPs resulting in endosomal escape of AuNP clusters, and produce a high gene silencing efficiency by releasing siRNA in the cytosol. Furthermore, the cluster formation of AuNPs accelerated photothermal ablation of cells when irradiated with laser. Precise and synchronized biomechanical motion in subcellular microenvironment is realized through judicious integration of pH-responsive behavior of the i-motif DNA and AuNPs, and meticulous designing of DNA

Graphene Oxide–Polyethylenimine Nanoconstruct as a Gene Delivery Vector and Bioimaging Tool

Graphene oxide (GO) has attracted an increasing amount of interest because of its potential applications in biomedical fields such as biological imaging, molecular imaging, drug/gene delivery, and cancer therapy. Moreover, GO could be fabricated by modifying its functional groups to impart specific functional or structural attributes. This study demonstrated the development of a GO-based efficient gene delivery carrier through installation of polyethylenimine, a cationic polymer, which has been widely used as a nonviral gene delivery vector. It was revealed that a hybrid gene carrier fabricated by conjugation of low-molecular weight branched polyethylenimine (BPEI) to GO increased the effective molecular weight of BPEI and consequently improved DNA binding and condensation and transfection efficiency. Furthermore, this hybrid material facilitated sensing and bioimaging because of its tunable and intrinsic electrical and optical properties. Considering the extremely high transfection efficiency comparable to that of high-molecular weight BPEI, high cell viability, and its application as a bioimaging agent, the BPEI–GO hybrid material could be extended to siRNA delivery and photothermal therapy

Miktoarm Amphiphilic Block Copolymer with Singlet Oxygen-Labile Stereospecific β‑Aminoacrylate Junction: Synthesis, Self-Assembly, and Photodynamically Triggered Drug Release

Incorporation of a desired stimuli-responsive unit in a stereospecific manner at the specific location within a nonlinear block copolymer architecture is a challenging task in synthetic polymer chemistry. Herein, we report a facile and versatile method to synthesize AB₂ miktoarm block copolymers bearing a singlet oxygen (¹O₂)-labile regio and stereospecific β-aminoacrylate linkage with 100% <i>E</i>-configuration at the junction via a combination of amino-yne click chemistry and ring opening polymerization. Using this strategy, a series of ¹O₂-responsive AB₂ amphiphilic miktoarm (MA) copolymers composed of hydrophilic polyethylene glycol (PEG) as the A constituent and hydrophobic polycaprolactone (PCL) as the B constituent (MA-PEG-<i>b</i>-PCL₂) was synthesized by varying the block length of PCL. The self-assembly characteristics of these well-defined MA-PEG-<i>b</i>-PCL₂ copolymers in an aqueous condition were studied by solvent displacement and thin-film hydration method, and their morphologies were investigated using transmission electron microscopy. The copolymers formed spherical, cylindrical, or lamella morphologies, depending on the chain length and preparation conditions. A hydrophobic photosensitizer chlorin e6 (Ce6) and anticancer drug doxorubicin (DOX) were efficiently encapsulated into the hydrophobic core of MA-PEG-<i>b</i>-PCL₂ copolymer micelles. These coloaded micelles were taken up by human breast cancer (MDA-MB-231) cells. Upon red laser light irradiation, the ¹O₂-generated by the Ce6 induced photocleavage of the β-aminoacrylate moiety, leading to the dissociation of the micellar structure and triggered intracellular drug release for effective therapy. Overall, rapid disassembly upon ¹O₂ generation and subsequent controlled intracellular drug release suggested that these micelles bearing β-aminoacrylate linkage have a huge potential for on-demand drug delivery