Ultrasound-Responsive Aqueous Two-Phase Microcapsules for On-Demand Drug Release

Traditional implanted drug delivery systems cannot easily change their release profile in real time to respond to physiological changes. Here we present a microfluidic aqueous two-phase system to generate microcapsules that can release drugs on demand as triggered by focused ultrasound (FUS). The biphasic microcapsules are made of hydrogels with an outer phase of mixed molecular weight (MW) poly(ethylene glycol) diacrylate that mitigates premature payload release and an inner phase of high MW dextran with payload that breaks down in response to FUS. Compound release from microcapsules could be triggered as desired; 0.4 μg of payload was released across 16 on-demand steps over days. We detected broadband acoustic signals amidst low heating, suggesting inertial cavitation as a key mechanism for payload release. Overall, FUS-responsive microcapsules are a biocompatible and wirelessly triggerable structure for on-demand drug delivery over days to weeks.

Alginate-azo/chitosan nanocapsules in vitro drug delivery for hepatic carcinoma cells: UV-stimulated decomposition and drug release based on trans-to-cis isomerization

In this study, a nanocapsule (AL-azo/CH) was prepared with the anionic alginate-azo (AL-azo) and cationic chitosan (CH) via layer-by-layer method. Doxorubicin hydrochloride (DOX), an anticancer drug, was entrapped inside the AL-azo nanocapsules to form the DOX-loaded nanocapsules (DOX/AL-azo/CH). When the DOX/AL-azo/CH nanocapsules were irradiated with 365-nm light, the electrostatic attraction between the layers would be weakened as the trans-to-cis isomerization of AL-azo, which would lead to the UV-responsive decomposition and drug-release. Furthermore, cellular experiments showed that DOX/AL-azo/CH nanocapsules could be endocytosed by the HepG2 cells, and the confocal laser scanning microscope images showed that the DOX fluorescence intensity became stronger with the prolonging of irradiation time, indicating that the intracellular DOX-release could be controlled by UV irradiation. The AL-azo/CH nanocarriers were UV-triggered decomposition and drug-release, which stepped further towards the next-generation of nano-therapeutics with spatial and temporal external control in the field of polysaccharide.

Luminescent PMMA Films and PMMA@SiO2 Nanoparticles with Embedded Ln3+ Complexes for Highly Sensitive Optical Thermometers in the Physiological Temperature Range*

In recent years, luminescent materials doped with Ln³⁺ ions have attracted much attention for their application as optical thermometers based on both downshifting and upconversion processes. This study presents research done on the development of highly sensitive optical thermometers in the physiological temperature range based on poly(methyl methacrylate) (PMMA) films doped with two series of visible Ln³⁺ complexes (Ln³⁺ =Tb³⁺ , Eu³⁺ , and Sm³⁺ ) and SiO₂ nanoparticles (NPs) coated with these PMMA films. The best performing PMMA film doped with Tb³⁺ and Eu³⁺ complexes was the PMMA[TbEuL₁ tppo]1 film (L₁ =4,4,4-trifluoro-1-phenyl-1,3-butadionate; tppo=triphenylphosphine oxide), which showed good temperature sensing of S_r =4.21 % K^-1 at 313 K, whereas for the PMMA films doped with Tb³⁺ and Sm³⁺ complexes the best performing was the PMMA[TbSmL₂ tppo]3 film (L₂ =4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadionate), with S_r =3.64 % K^-1 at 313 K. Additionally, SiO₂ NPs coated with the best performing films from each of the series of PMMA films (Tb-Eu and Tb-Sm) and their temperature-sensing properties were studied in water, showing excellent performance in the physiological temperature range (PMMA[TbEuL₁ tppo]1@SiO₂ : S_r =3.84 % °C at 20 °C; PMMA[TbSmL₂ tppo]3@SiO₂ : S_r =3.27 % °C at 20 °C) and the toxicity of these nanoparticles on human cells was studied, showing that they were nontoxic.

A DNA-Azobenzene Nanopump Fueled by Upconversion Luminescence for Controllable Intracellular Drug Release

Stimulus-responsive drug release possesses considerable significance in cancer therapy. This work reports an upconversion-luminescence-fueled DNA-azobenzene nanopump for rapid and efficient drug release. The nanopump is constructed by assembling the azobenzene-functionalized DNA strands on upconversion nanoparticles (UCNPs). Doxorubicin (DOX) is loaded in the nanopump by intercalation in the DNA helix. Under NIR light, the UCNPs emit both UV and visible photons to fuel the continuous photoisomerization of azo, which acts as an impeller pump to trigger cyclic DNA hybridization and dehybridization for controllable DOX release. In a relatively short period, this system demonstrates 86.7 % DOX release. By assembling HIV-1 TAT peptide and hyaluronic acid on the system, targeting of the cancer-cell nucleus is achieved for perinuclear aggregation of DOX and enhanced anticancer therapy. This highly effective drug delivery nanopump could contribute to chemotherapy development.

Multilayer Capsules Inside Biological Systems: State-of-the-Art and Open Challenges

There are many reports about the interaction of multilayer capsules with biological systems in the literature. A majority of them are devoted to the in vitro study with two-dimensional cell cultures. Multilayer capsule fabrication had been under intensive investigation from 1990s and 2000s by Prof. Helmuth Möhwald, and many of his followers further developed their own research directions, focusing on capsule implementation in various fields of biology and medicine. The aim of this future article is to consistently consider the most recent advances in cell-capsule interactions for different biomedical applications, including functionalization of clinically relevant cells, nonviral gene delivery, magnetization of cells to control their movement, and in vivo drug delivery. Finally, the description and discussion of the new trends and perspectives for improved functionalities of capsules in design and functionalization of cell-assisted drug vehicles are the major topics of this work.

Near-Infrared Triggered Decomposition of Nanocapsules with High Tumor Accumulation and Stimuli Responsive Fast Elimination

A near-infrared (NIR) induced decomposable polymer nanocapsule is demonstrated. The nanocapsules are fabricated based on layer-by-layer co-assembly of azobenzene functionalized polymers and up/downconversion nanoparticles (U/DCNPs). When the nanocapsules are exposed to 980 nm light, ultraviolet/visible photons emitted by the U/DCNPs can trigger the photoisomerization of azobenzene groups in the framework. The nanocapsules could decompose from large-sized nanocapsule to small U/DCNPs. Owing to their optimized original size (ca. 180 nm), the nanocapsules can effectively avoid biological barriers, provide a long blood circulation (ca. 5 h, half-life time) and achieve four-fold tumor accumulation. It can fast eliminate from tumor within one hour and release the loaded drugs for chemotherapy after NIR-induced dissociation from initial 180 nm capsules to small 20 nm U/DCNPs.

Triplex DNA Nanostructures: From Basic Properties to Applications

Triplex nucleic acids have recently attracted interest as part of the rich "toolbox" of structures used to develop DNA-based nanostructures and materials. This Review addresses the use of DNA triplexes to assemble sensing platforms and molecular switches. Furthermore, the pH-induced, switchable assembly and dissociation of triplex-DNA-bridged nanostructures are presented. Specifically, the aggregation/deaggregation of nanoparticles, the reversible oligomerization of origami tiles and DNA circles, and the use of triplex DNA structures as functional units for the assembly of pH-responsive systems and materials are described. Examples include semiconductor-loaded DNA-stabilized microcapsules, DNA-functionalized dye-loaded metal-organic frameworks (MOFs), and the pH-induced release of the loads. Furthermore, the design of stimuli-responsive DNA-based hydrogels undergoing reversible pH-induced hydrogel-to-solution transitions using triplex nucleic acids is introduced, and the use of triplex DNA to assemble shape-memory hydrogels is discussed. An outlook for possible future applications of triplex nucleic acids is also provided.

Composite-walled magnetic microcapsules at the water-toluene interface by ligand polymerization

The liquid-liquid interface has been exploited as a platform for devising gold and iron oxide nanoparticle (NP)-decorated composite microcapsules (MCs) by cross-linking between -OH groups of poly(ethylene glycol) (PEG) attached to the iron oxide (Fe3O4) nanoparticle surface and starch attached to the gold (Au) nanoparticle surface in the presence of terephthaloyl chloride as a cross-linker. These nanoparticle-decorated capsules form a shell of both types of nanoparticles with water as the minor phase and toluene as the major phase. The morphology of these capsules has been characterized by optical, transmission, and scanning electron microscopy images, and the polymerization reaction has been established by UV-vis and FTIR spectroscopic studies. The magnetic behavior of the capsules has been illustrated by using an external magnetic field to tailor the magnetic control of the capsules. The encapsulated phase was impregnated with dye molecules of three different sizes, viz., fluorescein isothiocyanate and its dextran conjugates, to investigate the permeability of the capsule wall by fluorescence spectroscopy. Interestingly, the microcapsules exhibit size-selective permeability across the capsule wall that points to their plausible applications in controlled encapsulation and release.

Chaotropic-anion-induced supramolecular self-assembly of ionic polymeric micelles

Traditional micelle self-assembly is driven by the association of hydrophobic segments of amphiphilic molecules forming distinctive core-shell nanostructures in water. Here we report a surprising chaotropic-anion-induced micellization of cationic ammonium-containing block copolymers. The resulting micelle nanoparticle consists of a large number of ion pairs (≈60,000) in each hydrophobic core. Unlike chaotropic anions (e.g. ClO4(-)), kosmotropic anions (e.g. SO4(2-)) were not able to induce micelle formation. A positive cooperativity was observed during micellization, for which only a three-fold increase in ClO4(-) concentration was necessary for micelle formation, similar to our previously reported ultra-pH-responsive behavior. This unique ion-pair-containing micelle provides a useful model system to study the complex interplay of noncovalent interactions (e.g. electrostatic, van der Waals, and hydrophobic forces) during micelle self-assembly.

Gold nanoparticles and gold nanoparticle-conjugates for delivery of therapeutic molecules. Progress and challenges

Gold nanoparticles and their conjugates as drug delivery vehicles for selective targeting of cancer cells.

Monitoring pH-triggered drug release from radioluminescent nanocapsules with X-ray excited optical luminescence

One of the greatest challenges in cancer therapy is to develop methods to deliver chemotherapy agents to tumor cells while reducing systemic toxicity to noncancerous cells. A promising approach to localizing drug release is to employ drug-loaded nanoparticles with coatings that release the drugs only in the presence of specific triggers found in the target cells such as pH, enzymes, or light. However, many parameters affect the nanoparticle distribution and drug release rate, and it is difficult to quantify drug release in situ. In this work, we show proof-of-principle for a "smart" radioluminescent nanocapsule with an X-ray excited optical luminescence (XEOL) spectrum that changes during release of the optically absorbing chemotherapy drug, doxorubicin. XEOL provides an almost background-free luminescent signal for measuring drug release from particles irradiated by a narrow X-ray beam. We study in vitro pH-triggered release rates of doxorubicin from nanocapsules coated with a pH-responsive polyelectrolyte multilayer using HPLC and XEOL spectroscopy. The doxorubicin was loaded to over 5% by weight and released from the capsule with a time constant in vitro of ∼36 days at pH 7.4 and 21 h at pH 5.0, respectively. The Gd₂O₂S:Eu nanocapsules are also paramagnetic at room temperature with similar magnetic susceptibility and similarly good MRI T₂ relaxivities to Gd₂O₃, but the sulfur increases the radioluminescence intensity and shifts the spectrum. Empty nanocapsules did not affect cell viability up to concentrations of at least 250 μg/mL. These empty nanocapsules accumulated in a mouse liver and spleen following tail vein injection and could be observed in vivo using XEOL. The particles are synthesized with a versatile template synthesis technique which allows for control of particle size and shape. The XEOL analysis technique opens the door to noninvasive quantification of drug release as a function of nanoparticle size, shape, surface chemistry, and tissue type.

NIR-activated content release from plasmon resonant liposomes for probing single-cell responses

Technological limitations have prevented the interrogation and manipulation of cellular activity in response to bioactive molecules within model and living systems that is required for the development of diagnostic and treatment modalities for diseases, such as cancer. In this work, we demonstrate that gold-coated liposomes are capable of encapsulation and on-demand release of signaling molecules with a spatial and temporal resolution leading to activation of individual cells. As a model system, we used cells modified to overexpress a certain G-protein coupled receptor, the CCK2 receptor, and achieved its activation in a single cell via the localized release of its agonist. This content release was triggered by illumination of the liposomes at wavelengths corresponding to the plasmon resonance of the gold coating. The use of plasmon resonant liposomes may enable on-demand release of a broad range of molecules using biologically safe near-infrared light and without molecule chemical modification. In combination with the spectral tunability of plasmon resonant coating, this technology may allow for multiplexed interrogation of complex and diverse signaling pathways in model or living tissues with unprecedented spatial and temporal control.