New technique to freeze brain tissue without harm

A team of medical researchers has developed a technique to freeze and thaw brain tissue without causing damage.
In their study, published in the journal Cell Reports Methods, the group tested bathing brain organoid tissue in candidate chemicals before freezing them using liquid nitrogen.

Prior research has shown that no matter how quickly brain matter is frozen, the freezing and thawing process always causes tissue damage. This has made it more difficult for researchers to study brain matter because research must be conducted immediately after obtaining a tissue sample. In this new effort, the team  found a way around this problem by soaking the tissue in a special solution before freezing.

The work involved dipping or soaking brain organoids (brain tissue grown from stem cells) in candidate compounds and then freezing and thawing them to see how they fared. After many attempts, they found one combination of solutions that worked best—a mix of ethylene glycol, methylcellulose DMSO and Y27632. They named the solution mix MEDY.

The research team then tested MEDY under a variety of conditions to see how well it prevented damage from freezing. The conditions involved changing variables, such as the age of the organoids prior to freezing and how long they were soaked in a MEDY solution. They then allowed the organoids to resume growing after they were thawed for up to 150 days.

The researchers found little difference between organoids that had been frozen and those that had not—even those that had been frozen for as long as 18 months.

As a final test, the research team used their technique on a sample of brain tissue obtained from a live human patient and found that it worked just as well.

The research team suggests that their technique should allow researchers to store brain tissue samples on a scale large enough to allow for new types of brain and nervous system research.

Weiwei Xue et al, Effective cryopreservation of human brain tissue and neural organoids, Cell Reports Methods (2024). DOI: 10.1016/j.crmeth.2024.100777

Microplastics may slow the rate at which carbon is pulled from the sea surface to the depths

Plastics in the ocean do more harm than suffocate turtles, fish and other marine life.

A new study  shows that microplastics may reduce the ability of the ocean to help offset the climate crisis by slowing down the rate at which carbon is taken from the sea surface to the depths.

For millennia, the ocean has been part of a carbon sink process in which dead phytoplankton clump together and fall into the deep ocean in showers of what look like "marine snow". The resulting carbon sequestration is a marine version of how trees and plants on terrestrial Earth take carbon from the atmosphere and store it in soil.

But new research  shows that microplastics in the ocean are slowing the process down by making the "marine snow" more buoyant. Plastics want to float. If phytoplanktons grow on microplastics in biofilms, instead of as free living organisms, that changes the buoyancy of the phytoplankton when they die.

Basically, the plastics are slowing down the sinking rate of the marine snow, which is potentially reducing the efficiency with which the ocean can remove carbon dioxide from the atmosphere.

So microplastics  could be a threat to global scale processes, such as the carbon cycle that is so important for all life.

 Kai Ziervogel et al, Microbial interactions with microplastics: Insights into the plastic carbon cycle in the ocean, Marine Chemistry (2024). DOI: 10.1016/j.marchem.2024.104395