Technological progress often involves miniaturization. So, what can miniaturization do for single-cell analysis? Let’s consider single cells that are compartmentalized and analyzed for secreted products such as antibodies. The larger the volume of each compartment, the greater the problem posed by the diffusion of secreted products away from cells. Sensitivity suffers.
If the compartments are the wells in a 96-well microplate, one way to improve sensitivity is to switch from microplates to microfluidic chips. However, these chips may need to be used in conjunction with specialized instrumentation, which can lower throughput even as it increases costs.
Such difficulties were confronted by doctoral candidate Joe de Rutte when he worked in the lab headed by Dino Di Carlo, PhD, at the University of California, Los Angeles (UCLA). de Rutte was contributing to the lab’s efforts to reimagine microfluidics so that it could become more functional and more approachable for bench scientists.
“We created a reagent solution for problems that are traditionally addressed with niche instruments,” de Rutte says. The solution—suspendable hydrogel-based microcarriers—was described by de Rutte and colleagues as way to democratize access to high-throughput functional cell screening (ACS Nano 2022; 16: 7242–7257).
The microcarriers, which de Rutte is now helping to commercialize as CEO of Partillion Bioscience, are microscale, bowl-shaped particles that are mixed with cells in a standard test tube. With each particle cavity acting as an individual cell chamber, scientists can screen between 10,000 and one million cells per test tube.
Partillion’s microcarriers are called Nanovials. They are available in 35 and 50 µm sizes (marginally larger than most human cells), and they hold volumes of less than 1 nanoliter. The volume of a 96-well microplate, in contrast, is approximately 300 microliters, more than a hundred thousand times larger.
“Our Nanovials enable the isolation of single cells and the precise capture of secreted antibodies with exceptional sensitivity,” de Rutte asserts. “Unlike traditional methods, Nanovials seamlessly integrate into existing workflows, so researchers can leverage their current equipment. This simplifies the process and significantly enhances screening throughput and diversity, which leads to faster and more accurate identification of promising antibody candidates.”
Di Carlo and colleagues have likened microcarrier platforms to software applications, or apps, in that each, in its own sphere, is compatible with standard infrastructure: “[Microcarrier platforms can run on] ubiquitous life sciences instrument hardware, fueling more rapid adoption and expanded impact” (Anal. Chem. 2024; 96: 7817–7839).
A learning experience
A summer spent working in the BioHybrid Systems Lab at the University of Tokyo in 2015, while a graduate student at the University of California, Santa Barbara, taught de Rutte to think in new ways. “This was a very multidisciplinary lab,” de Rutte says. “The 40 to 50 people working there approached science with creativity. A lot of their projects were pretty far out, like making chemical sensors similar to the olfactory receptors from mosquitoes. The lab’s culture was all about rapid innovation and the creative mixing of ideas. Concepts often moved from idea to prototype in just a day.”
“It was the combination of this creativity with the purpose-driven research I later encountered in the Di Carlo lab that truly made the difference,” de Rutte reflects. “The fusion of these two environments—the exploratory freedom in Tokyo, and the focused, application-driven work at UCLA—was essential. Without both, the Nanovial technology might never have been realized.”
The greatest catalyst in terms of forming Partillion, de Rutte says, was the reaction to his presentation, “High-Throughput Encapsulation and Selection of Cells Based on Antibody Secretion Using Lab-on-a-Particle Technology,” at the Society of Lab Automation and Screening 2020 conference: “I won the Innovation Award—the top award given to a researcher presenting there.”
This validation reinforced de Rutte’s confidence in the technology he had developed with Di Carlo. In 2020, when COVID-19 hit and many labs were closed, they co-founded Partillion. “We started putting together a pitch deck, applying for research grants, and looking for incubator space,” he recalls. Initial financing came from friends and family, a Small Business Innovation Research grant, and pre-seed funding from two venture groups. Partillion closed its first $5 million seed round in late 2022. It also has revenue from customers in the United States, and it will soon have revenue from customers in Japan.
de Rutte transitioned into the CEO role without biopharma management experience. To fill that expertise gap, he tapped veteran biopharma and investment firm executives as advisors.
Unique market position
“We’re in a unique spot in the market, and this has given us a lot of flexibility,” de Rutte remarks. Specifically, it helped Partillion go to market quickly and build market share by leveraging equipment that people already can access in their laboratories.
de Rutte says that for many budget-
constrained researchers accustomed to hybridoma screening and other legacy approaches, this is the “first time they’ve been able to access such sophisticated techniques as direct plasma cell screening or other single-cell assays that characterize antibody function.” He adds that even large labs accustomed to sophisticated microfluidic screening technologies are finding value in Nanovials, which enable fast startup and the screening of more cells than normally expected.
Antibody discovery and more
“We’re seeing a lot of interest in antibody discovery, and there’s still a lot of opportunity,” de Rutte says. “For example, we’ve been working to develop and improve our workflows for screening cell membrane targets such as ion channels and G protein–coupled receptors. They can be challenging to screen because they are hard to express recombinantly.”
Partillion has launched an early-access program for its high-throughput multicell screening workflow. The new format enables scientists to localize an antibody-secreting cell and a cell expressing a target protein on its membrane. de Rutte notes that the company is looking beyond the antibody space to anywhere scientists need to compartmentalize cells or cell products.
According to de Rutte, a key challenge for the company is to focus on “providing better guidance around some of the ubiquitous parts of the workflows to better support the instruments that interface with [our products].” He acknowledges that maintaining this focus can be difficult, given the company’s size: “We’re a smaller team, so it’s imperative that the team understands where best to focus its efforts for immediate benefits, while also exploring areas that will lead to future progress.”
Partillion is bringing its technology to Japan through a distribution agreement with Sony. “Our technology is compatible with a lot of different instruments from Sony and other technology groups,” de Rutte points out, so additional agreements appear to be in the works. The company also is developing the Nano-SEEDS Program to actively support academic endeavors to build next-generation assays.
To create the conditions for sustainable growth, Partillion is working to expand its customer base and optimize its operations. “As we achieve these goals,” de Rutte declares, “we’re confident that profitability will naturally follow.”
