Chitosan—one of the natural multifunctional polymers—due to its unique and versatile biological properties is regarded as a useful compound in medical and pharmaceutical technology. Recently, considerable research effort has been made in order to develop safe and efficient chitosan products. However, the problem of poor stability of chitosan-based systems restricts its practical applicability; thus, it has become a great challenge to establish sufficient shelf-life for chitosan formulations. Improved stability can be assessed by controlling the environmental factors, manipulating processing conditions (e.g., temperature), introducing a proper stabilizing compound, developing chitosan blends with another polymer, or modifying the chitosan structure using chemical or ionic agents. This review covers the influence of internal, environmental, and processing factors on the long-term stability of chitosan products. The aim of this paper is also to highlight the latest developments which enable the physicochemical properties of chitosan-based applications to be preserved upon storage.

https://www.mdpi.com/1660-3397/13/4/1819/pdf

Stability of chitosan-a challenge for pharmaceutical and biomedical applications.

This disclosure provides methods and compositions for sample processing, particularly for sequencing applications. Included within this disclosure are bead compositions, such as diverse libraries of beads attached to large numbers of oligonucleotides containing barcodes. Often, the beads provides herein are degradable. For example, they may contain disulfide bonds that are susceptible to reducing agents. The methods provided herein include methods of making libraries of barcoded beads as well as methods of combining the beads with a sample, such as by using a microfluidic device.

Compositions and methods for sample processing

This disclosure provides microwell capsule array devices. The microwell capsule array devices are generally capable of performing one or more sample preparation operations. Such sample preparation operations may be used as a prelude to one more or more analysis operations. For example, a device of this disclosure can achieve physical partitioning and discrete mixing of samples with unique molecular identifiers within a single unit in preparation for various analysis operations. The device may be useful in a variety of applications and most notably nucleic-acid-based sequencing, detection and quantification of gene expression and single-cell analysis.

Capsule array devices and methods of use

Provided herein are methods, compositions, and kits for assays, many of which involve amplification reactions such as digital PCR or droplet digital PCR. The assays may be used for such applications as sequencing, copy number variation analysis, and others. In some cases, the assays involve subdividing a sample into multiple partitions (e.g., droplets) and merging the partitions with other partitions that comprise adaptors with barcodes.

Methods and compositions for nucleic acid analysis

The present disclosure provides compositions, methods, systems, and devices for polynucleotide processing. Such polynucleotide processing may be useful for a variety of applications, including polynucleotide sequencing.

Methods and systems for processing polynucleotides

The present invention generally relates to emulsions, and more particularly, to multiple emulsions In one aspect, multiple emulsions are formed by urging a fluid into a channel, eg, by causing the fluid to enter the channel as a "jet" Side channels can be used to encapsulate the fluid with a surrounding fluid In some cases, multiple fluids may flow through a channel collinearly before multiple emulsion droplets are formed The fluidic channels may also, in certain embodiments, include varying degrees of hydrophilicity or hydrophobicity As examples, the fluidic channel may be relatively hydrophilic upstream of an intersection (or other region within the channel) and relatively hydrophobic downstream of the intersection, or vice versa In some cases, the average cross-sectional dimension may change, eg, at an intersection For instance, the average cross-sectional dimension may increase at the intersection Surprisingly, a relatively small increase in dimension, in combination with a change in hydrophilicity of the fluidic channel, may delay droplet formation of a stream of collinearly-flowing multiple fluids under certain flow conditions; accordingly, the point at which multiple emulsion droplets are formed can be readily controlled within the fluidic channel In some cases, the multiple droplet may be formed from the collinear flow of fluids at (or near) a single location within the fluidic channel In addition, unexpectedly, systems such as those described herein may be used to encapsulate fluids in single or multiple emulsions that are difficult or impossible to encapsulate using other techniques, such as fluids with low surface tension, viscous fluids, or viscoelastic fluids Other aspects of the invention are generally directed to methods of making and using such systems, kits involving such systems, emulsions created using such systems, or the like

Multiple emulsions created using jetting and other techniques

The present invention generally relates to emulsions, and more particularly, to double and other multiple emulsions. Certain aspects of the present invention are generally directed to the creation of double emulsions and other multiple emulsions at a common junction of microfluidic channels. In some cases, the microfluidic channels at the common junction may have substantially the same hydrophobicity. In one set of embodiments, a device may include a common junction of six or more channels, where a first fluid flows through one channel, a second fluid flows through two channels, and a third or carrying fluid flows through two more channels, such that a double emulsion of a first droplet of the first fluid, contained in a second droplet of the second fluid, contained by the carrying fluid, flows away from the common junction through a sixth channel. Other aspects of the invention are generally directed to methods of making and using such systems, kits involving such systems, emulsions created using such systems, or the like.

Control of emulsions, including multiple emulsions

Articles and methods for controlling flow in fluidic Systems, especially in microfluidic Systems, are provided. A microfluidic System includes a configuration such that the actuation of a single valve can allow the switching of fluids from a first fluid path (e.g., a first channel section) to a second fluid path (e.g., a second channel section). This may be achieved by incorporating a valve (38) with a first channel section (24), which may have a lower hydrodynamic resistance than a second channel section (28)prior to actuation of the valve. Actuation of the valve (38) can cause only the hydrodynamic resistance of the first channel section (24) to increase, thereby redirecting fluid flow into the second channel section (28) (which now has a relatively lower hydrodynamic resistance). The valve comprises a control channel (40) for introducing a positive or reduced pressure, and is adapted to modulate fluid flow in an adjacent channel section by constricting or expanding the channel section (24).

Valves and other flow control in fluidic systems including microfluidic systems

The present invention generally relates to microfluidics and epigenetic sequencing. In one set of embodiments, cells contained within a plurality of microfluidic droplets are lysed and the DNA (e.g., from nucleosomes) within the droplets are labeled, e.g., with adapters containing an identification sequence. The adapters may also contain other sequences, e.g., restriction sites, primer sites, etc., to assist with later analysis. After labeling with adapters, the DNA from the different cells may be combined and analyzed, e.g., to determine epigenetic information about the cells. For example, the DNA may be separated on the basis of certain modifications (e.g., methylation), and the DNA from the separated nucleosomes may be sequenced using techniques such as chromatin immunoprecipitation ("ChIP"). In some cases, the DNA sequences may also be aligned with genomes, e.g., to determine which portions of the genome were epigenetically modified, e.g., via methylation.

Systems and methods for epigenetic sequencing

The present invention generally relates to emulsions, and more particularly, to multiple emulsions. In one aspect, multiple emulsions are formed using a plurality of channels, such as microfluidic channels, that meet at a common intersection. The multiple emulsions may be created at a single common intersection in some embodiments, unlike other prior art systems where multiple channel intersections are required to create multiple emulsions. For instance, in one set of embodiments, three, four, or more microfluidic channels may intersect at a common intersection, with two or three serving as inlets and one serving as the outlet. In some embodiments, a first fluidic channel may be relatively hydrophobic, while a second fluidic channel is relatively hydrophilic. The third channel, if present, may be relatively hydrophilic or hydrophobic, depending on the application. The outlet channel may be hydrophobic, hydrophilic, or may comprise at least one portion that is relatively hydrophilic and at least one portion that is relatively hydrophilic. By controlling the flow of fluids through the hydrophilic and hydrophobic portions of the channels, multiple emulsions may be created proximate the common intersection, due to interactions between the fluids entering the common intersection. In other embodiments, different patterns of hydrophilic or hydrophobic channels may be used. Other aspects of the invention are generally directed to methods of making and using such systems, kits involving such systems, emulsions created using such systems, or the like.

Multiple emulsions created using junctions

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