A method and system are described for processing tissues according to particular processing protocols that are established based on time-of-flight measurements as a processing fluid is diffused into a tissue sample. In one embodiment, measurement of the time it takes about 70% ethanol to diffuse into a tissue sample is used to predict the time it will take to diffuse other processing fluids into the same or similar tissue samples. Advantageously, the disclosed method and system can reduce overall processing times and help ensure that only samples that require similar processing conditions are batched together.

The present invention relates to systems and methods for tissue processing and analysis. Tissue chambers are configured to allow single-container chemical processing, imaging, and wax embedding of tissue samples in a single container without manipulation between steps. Tissue chambers with features to support the tissue sample and allow fluid flow between the tissue sample and the tissue chamber surface are disclosed. The features may be index matched to sample structures of interest or dissolvable in clearing solution to allow for in-chamber imaging with minimal distortion. Specialized tissue processing and wax removal apparatuses are also disclosed including for use with tissue chambers having frangible portions to permit ease of wax removal.

An extended tissue fixation method is provided including at least one soak in a cold aldehyde-based fixative solution followed by a soak in a warm aldehyde-based fixative solution over a period greater than 2 days. Using the processes disclosed herein, improved tissue morphology and IHC staining as well as superior preservation of post-translation modification signals, e.g. biomarkers, have been accomplished relative to standard room temperature fixation protocols. Moreover, the tissue can be left in the fixative solution up to at least 14 days using these methods, which provides improved flexibility relative to other protocols, enabling fixation to be conducted during transportation, shipping, and over weekends or vacations, while still achieving acceptable staining results.

Methods, kits, and systems for fixation of RNA permitting its detection in intact tissue, such as, large volume of mammalian tissue are disclosed. The methods, kits, and systems utilize carbodiimide-based chemistry to stably retain RNAs in tissue clarified using CLARITY. Also provided herein are methods, kits, and systems for detection of RNAs in clarified tissue.

In various embodiments, the present application teaches methods and compositions for tissue clearing in which whole organs and bodies are rendered macromolecule-permeable and optically-transparent, thereby exposing their cellular structure with intact connectivity. In some embodiments, the present application teaches PACT, a protocol for passive tissue clearing and immunostaining of intact organs. In other embodiments, the present application teaches RIMS, a refractive index matching media for imaging thick tissue. In yet other embodiments, the application teaches PARS, a method for whole-body clearing and immunolabeling.

Methods of isolating and assaying fetal extravillous trophoblast cells, including assays of RNA of the fetal extravillous trophoblast cells according to aspects of the disclosure include obtaining a maternal endocervical sample containing fetal extravillous trophoblast cells from a pregnant subject; fixing the maternal endocervical sample in an aldehyde fixative, removing fetal extravillous trophoblast cells from the maternal endocervical sample thereby producing isolated extravillous trophoblast cells, isolating and assaying RNA from the fetal extravillous trophoblast cells.

A novel fixation method is presented that will circumvent both biological and safety concerns with current fixation methods.

The invention discloses a hard tissue slice anti-falling pretreatment device which comprises a box and a slice frame, a buffer plate is arranged in the box, and a plurality of small holes are evenly formed in the buffer plate; the bottom of the box is communicated with a liquid discharge pipe through a liquid outlet, and the liquid discharge pipe is provided with a valve; the slice frame is arranged on the buffer plate and comprises two longitudinal support frames and a plurality of layers of transverse support frames fixed between the two longitudinal support frames; each layer of transverse support frame comprises a plurality of first support rods, the gradient of each first support rod relative to the horizontal plane is 0-15 degrees.

Described herein are methods, compositions, kits and systems for fixing biological samples. In one aspect, the method includes contacting the tissue sample with a fixing composition comprising about 20 to about 80% v/v DMSO. The solutions of the dehydration and clearing steps also include DMSO. Tissues fixed according to the methods described herein (and using the compositions herein described) may be fixed at a more rapid rate as compared to conventional procedures, but with comparable results.

An in vitro method is provided for analyzing chromatin accessibility and screening RNA of each single cell in a heterologous population (e.g., a library of cells). The method comprises incubating cell nuclei obtained from lysed cells with a transposome complex in a tagmentation buffer, performing reverse transcription wherein each of the RNAs is reverse transcribed to a DNA barcoded with the first barcode; sequencing DNA, which is extracted from digested cell nuclei; and analyzing chromatin accessibility and RNA of the cells. In a further embodiment, the method described comprises performing combinatorial cellular indexing and/or a perturbation step. Additionally, provided are a transposase TnY, buffer(s), and kit(s) for use in the described method.