A recent study published in the journal ‘Advanced Functional Materials’ revealed groundbreaking techniques to address the challenge of low capture rates when removing older cells from cultures. Rather than focusing solely on the removal of old cells, the researchers proposed a more favourable approach—preventing these cells from entering the state of senescence altogether.

As we age, our bodies undergo a natural process of change and degeneration called senescence. This senescence phenomenon also affects stem cells, which possess the remarkable capability to differentiate into different cell types. However, when it comes to maintaining cell cultures for therapeutic purposes, senescence poses a significant challenge. These cultured cells play a crucial role in producing vital biomolecules necessary for various medicines and treatments. Unfortunately, once the cells enter a senescent state, they not only cease producing these beneficial biomolecules but also start generating biomolecules that counteract the intended therapeutic effects, compounding the issue further.

Miller said, “We work with mesenchymal stem cells, which are derived from fat tissue, and produce biomolecules that are essential for therapeutics, so we want to keep the cell cultures healthy. In a clinical setting, the ideal way to prevent senescence would be to condition the environment that these stem cells are in, to control the oxidative state.” “With antioxidants, you can pull them the cells out of this senescent state and make them behave like a healthy stem cell.”

In the quest to delay senescence, the administration of antioxidants to cells has shown promise. However, conventional approaches for delivering antioxidants suffer from significant drawbacks, such as inconsistent and fluctuating drug release rates between cells and over time. Fortunately, a groundbreaking study conducted by the labs of Kong and Hee-Sun Han (GNDP/IGOH), led by Miller as the first author, introduces a novel antioxidant delivery method. This innovative approach offers enhanced reliability, long-lasting effects, and minimized variation, addressing the limitations of existing techniques.

Antioxidants are employed in the form of polymer-stabilized crystals. Unlike conventional methods that involve crystal growth within reactors, this technique leverages microfluidics—an advanced technology enabling precise manipulation of minute fluid volumes. By utilizing microfluidics, the research team successfully produces uniformly-sized crystals with consistent dosages. Consequently, this breakthrough methodology significantly reduces variations in drug release among cells, enhancing the overall effectiveness and reliability of the antioxidant delivery system. “With microfluidics, each drop functions as a small reactor, such that we can get small, similar-sized, individual crystals, which minimizes variation in drug release rate,” said Miller.

Moreover, the crystals dissolve at a slower rate than traditional methods, making the release of the drug uniform over time, and increasing the duration of the drug’s effectiveness.

“We learned that the narrow variation in the drug’s release profile is really important,” explained Han. “When you add drugs that dissolve in water, there is this bursting period where a lot of it dissolves in the liquid at once, and not much later. But the crystal allows this uniform, extended-release, which helps maintain the tight range of optimal concentrations that are needed.”

“When typical antioxidants are put into water or biological fluid, they lose their vital activity within six hours,” described Kong. “But the new antioxidant crystal remains bioactive for at least two days, so we can actually extend the duration of the drug, and also reduce the frequency with which we have to add antioxidants to the cell culture media. This minimizes the variation in the type of the biomolecules the stem cells are generating and improves the reproducibility of the product, which is one of the biggest challenges in biomanufacturing at the moment.”

The prolonged efficacy of the drug enables stem cell cultures to remain in a non-senescent state for extended periods, resulting in a higher yield of essential biomolecules for therapeutic purposes. Furthermore, this method holds potential for patient-derived stem cell treatments, where biomolecules derived from the patient’s own body can aid in addressing tissue ailments like any disease or injuries.

“When we use biomolecules from donors instead of the patient, that can have a host effect,” explained Miller. “Ideally, we would harvest stem cells from the patient that we’re treating, grow them in a bioreactor, and harvest those biomolecules for that therapeutic. This works well for someone who is 20. Still, if we envision an elderly patient, they’re going to have a high population of these senescence cells, that are not going to be secreting the therapeutically relevant biomolecules. If we can pull those cells out of that state, and make them behave like a healthy cell, we can get a much larger load of therapeutically relevant biomolecules for the patient.”

The team aims to elevate the biomanufacturing process, yet this methodology has versatile applications beyond antioxidant delivery to stem cells. With many cell types experiencing senescence, this technique holds promise for diverse cell cultures in medicine and therapeutics. Additionally, the crystals can offer controlled and sustained delivery of antioxidants or other drugs directly into the targeted tissue of patients.