Droplets become encapsulated after falling into floating polymer films
Capsules are composed of a core, typically a liquid containing active substances, and a surrounding shell. They are used to ...delay the degradation of active ingredients, protect them from reacting or interacting with substances contained in the surrounding shell, or to prevent premature consumption of encapsulants (
1
,
2
). The performance of capsules is often determined by their permeability toward encapsulants and stability against rupture; these parameters can be adjusted with the composition, structure, and thickness of the shell (
3
,
4
). Mechanically robust capsules with a minimal permeability even toward low molecular weight substances often have rather thick shells (
5
). On page 775 of this issue, Kumar
et al.
(
6
) report an elegant process to fabricate capsules with very thin, rigid shells that display a low permeability even toward small encapsulants.
Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and ...tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.
The ideal nanoscale drug delivery vehicle allows control over the released dose in space and time. We demonstrate that this can be achieved by stealth liposomes comprising self-assembled ...superparamagnetic iron oxide nanoparticles (NPs) individually stabilized with palmityl-nitroDOPA incorporated in the lipid membrane. Alternating magnetic fields were used to control timing and dose of repeatedly released cargo from such vesicles by locally heating the membrane, which changed its permeability without major effects on the environment.
Particles and capsules are used as containers for active ingredients to delay their degradation and control the location and kinetics of their release. Key to a successful application of these ...containers is a good control over their size, composition, and the release kinetics of encapsulants. These parameters can be tuned if containers are made from drops of a controlled size and composition; a method that enables formation of drops of a defined size is microfluidics. This review highlights some recent developments in the use of drops made with microfluidics to produce particles and capsules of controlled sizes, compositions, and structures.
Microfluidics: Thermo‐ and photoresponsive polymersomes are assembled using capillary microfluidic devices. Encapsulants can be selectively released from the thermoresponsive polymersomes if they are ...incubated at and above temperatures of 40 °C, whereas the photoresponsive polymersomes selectively release encapsulants if illuminated with laser light (see picture; NP=nanoparticle).
The trend towards personalized medicine and the long-standing wish to reduce drug consumption and unwanted side effects have been the driving force behind research on drug delivery vehicles that ...control localization, timing and dose of released cargo. Controlling location and timing of the release allows using more potent drugs as the interaction with the right target is ensured and enables sequential drug release. A particularly desired solution allows for externally triggered release of encapsulated compounds. Externally controlled release can be accomplished if drug delivery vehicles, such as liposomes or polyelectrolyte multilayer capsules, incorporate nanoparticle (NP) actuators. However, close control over the structure of the composite material is necessary to harness this potential. This review describes the assembly and characterization of NP functionalized liposomes and polyelectrolyte multilayer capsules that allow for externally triggered cargo release. Special attention is paid to the relationship between NP stability and the assembly and performance of NP functionalized drug delivery vehicles.
How droplet microfluidics can be used to fabricate solid‐shelled microcapsules having precisely controlled release behavior is described. Glass capillary devices enable the production of monodisperse ...double emulsion drops, which can then be used as templates for microcapsule formation. The exquisite control afforded by microfluidics can be used to tune the compositions and geometrical characteristics of the microcapsules with exceptional precision. The use of this approach to fabricate microcapsules that only release their contents when exposed to a specific stimulus – such as a change in temperature, exposure to light, a change in the chemical environment, or an external stress – only after a prescribed time delay, and at a prescribed rate is reviewed.
Recent developments in fabricating and characterizing solid‐shelled microcapsules using microfluidically generated double emulsion templates are highlighted. This approach enables the design of microcapsules with release behavior tailored for specific applications.
Single-cell RNA sequencing (scRNA-seq) approaches have transformed our ability to resolve cellular properties across systems, but are currently tailored toward large cell inputs (>1,000 cells). This ...renders them inefficient and costly when processing small, individual tissue samples, a problem that tends to be resolved by loading bulk samples, yielding confounded mosaic cell population read-outs. Here, we developed a deterministic, mRNA-capture bead and cell co-encapsulation dropleting system, DisCo, aimed at processing low-input samples (<500 cells). We demonstrate that DisCo enables precise particle and cell positioning and droplet sorting control through combined machine-vision and multilayer microfluidics, enabling continuous processing of low-input single-cell suspensions at high capture efficiency (>70%) and at speeds up to 350 cells per hour. To underscore DisCo's unique capabilities, we analyzed 31 individual intestinal organoids at varying developmental stages. This revealed extensive organoid heterogeneity, identifying distinct subtypes including a regenerative fetal-like Ly6a
stem cell population that persists as symmetrical cysts, or spheroids, even under differentiation conditions, and an uncharacterized 'gobloid' subtype consisting predominantly of precursor and mature (Muc2
) goblet cells. To complement this dataset and to demonstrate DisCo's capacity to process low-input, in vivo-derived tissues, we also analyzed individual mouse intestinal crypts. This revealed the existence of crypts with a compositional similarity to spheroids, which consisted predominantly of regenerative stem cells, suggesting the existence of regenerating crypts in the homeostatic intestine. These findings demonstrate the unique power of DisCo in providing high-resolution snapshots of cellular heterogeneity in small, individual tissues.
High‐volume production of monodisperse droplets is of importance for industrial applications due to increased emulsion stability, precise control over droplet volumes, and the formation of periodic ...arranged structures. So far, parallelized microfluidic devices are limited by either their complicated channel geometry or by their chemically or thermally unstable embedding material. This study shows a scalable microfluidic step emulsification chip that enables production of monodisperse emulsions at a throughput of up to 25 mL h−1 in a glass device with 364 linearly parallelized droplet makers. The chemical and thermal stability of such a glass device allows for the preparation of a broad variety of functional particles and microdroplets by using any desired solvent together with nanoparticles, polymers, and hydrogels. Moreover, the microfluidic device can be stringently cleaned for nearly unlimited use and permits the alternating production of oil‐in‐water and water‐in‐oil emulsions. The combined high throughput, chemical and thermal stability offered by our device enables production of monodisperse functional materials for large‐scale applications.
High‐throughput production of monodisperse emulsions is attractive in material‐, food‐, and pharmaceutical sciences, since it provides precise control to create functional microcapsules and microparticles. This study combines the scalability of step emulsification with the chemical inertness of glass devices to enable the robust and high‐volume production of a broad variety of functional materials.
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