We spoke to a few members of the exciting research team in the Majumder lab at IIT-Bombay. Using microphysiological systems, they study mechanobiology by combining the principles of biology, chemistry, engineering, and physics! Their mantra? Keep it simple!

“In our lab, we try to keep things very uncomplicated, as much as we can.” chuckles Dr. Abhijit Majumder as he finishes explaining a seemingly straightforward yet intricate aspect of one of his lab’s research projects. During his time at IIT-Kanpur, The Institute for Stem Cell Science and Regenerative Medicine (inStem), Bangalore and Harvard Medical School, Boston, most of Dr. Majumder’s doctoral and post-doctoral work focused on cell mechanics and microfluidic devices.

Now, an Associate Professor atthe Indian Institute of Technology – Bombay, he spends his time with his students tackling the mystery of how the microenvironment within the body contributes to cellular growth, and how they can create affordable devices to be used in these studies! The basic tenets of the Majumder lab are to keep things cheap and stick to basic scientific principles.

All his students work on projects which seem incredibly complicated, but we quickly realized the theory behind allthese experiments was extremely straightforward. It’s all about keeping it simple!

Ketaki, a Ph.D. student in the Majumder lab, is working on two projects. Through a collaboration with Dr. Shilpee Dutt’s lab at ACTREC, Mumbai, she grows glioblastoma (a kind of brain cancer) cells on two separate bases; one is a regular tissue culture plate seen in labs worldwide, and the other is a polyacrylamide hydrogel. This gel has been tinkered with so that its stiffness matches that of the brain, a cool 0.5 kiloPascal.

Now, when grown in a plastic culture plate, these cells usually tend to form a single layer, after which they begin to clump together into structures called “tumoroids”. However, Ketaki noticed something different on the PA hydrogel. “The glioblastoma cells immediately formed tumoroids when they grew on this brain-like tissue,” she explains.

“This self-assembling property of tumour cells goes missing in 2D cell culture systems,” says Dr. Majumder. “We usually rely on the hanging drop technique, where cells are forced together to form 3D structures. But these cells form tumoroids in the brain without all these fancy things, right? We decided to mimic the brain microenvironment using a gel with the same thickness and behold! Our cells formed tumoroids right away!” Intriguing, isn’tit?

To Dr. Majumder and his students, it seemed that all the cells needed to form the correct shape was a familiar setting. Mechanobiology is rooted in investigating how physical forces and changes in the mechanical properties of cells and tissues influence cell growth and development, and even disease progression. “We simulate the brain microenvironment, focusing on tissue stiffness to test drugs and identify chemosensitivity using these glioblastoma cells,” says Ketaki.

Next, a picture of a mesh-like structure flashes on the screen; Ketaki explains hown she is developing a device which can deliver drug loads of various concentrations to cells. “Seeding cells one at a time into hundreds of wells and manually preparing various drug concentrations is incredibly timeconsuming, and increases the risk of human error. To combat this, we’ve worked with Professor Prasanna Gandhi at IIT-Bombay and come up with a microfluidic device that tackles all these problems.”

This teeny-tiny mesh-like structure, just 15mm in area can hold thousands of cells and allows a drug to diffuse across the device in a gradient, dispersing the drug to each cell cluster in a different concentration. “Each tiny node has an equal number of cells, in both 5×5 and 10×10 devices, meaning up to 100 concentrations can be studied at once! We were able to identify the IC50 (a measure used to study drug efficacy) of curcumin, an anti-cancer drug on brain cancer cells and validate the effectiveness of our device”.

Shital, who is also a collaborator in the drug gradient study, steps into our Zoom window next. “My work focuses on topography, which is basically the features of a surface. I work with different kinds of plants, cataloguing their topography and seeing how we can use natural surfaces to study the behaviour of cells,”. Naturally, our first question is how she thought of this idea! Dr. Majumder interrupts us, laughing. “The entire credit goes to Shital, she came up with this idea all by herself. I didn’t even wantto do it!”

Smiling, Shital explains “I was reading some papers about the structure of the intestine, focusing on how the bumpy folds increase its surface area. I noticed that the leaves of a lotus plant looked the same way! This was how my idea was born! I wondered how the characteristics of these natural surfaces could be used as models to study cellular behaviour”. Using these oddly shaped leaf surfaces, Shital creates a mould using PDMS (polydimethylsiloxane, a silicone-based organic polymer) and replicates the pattern seen on the leaf.

Have you ever used insects as a mould?” wonders Kadambari. “Nope!” comes a quick reply. “I’m very happy with my plants” laughs Shital. “I started my work with the Bambusoideae leaf. After replicating the leaf pattern onto a PDMS cast, I grew some muscle cells. These cells usually grow in a random manner on a flat surface. But when I grew it on the bamboo leaf pattern, the cells aligned themselves along the pattern of the leaf surface! I also noticed the same behaviour when I grew mesenchymal stem cells.”

These bio-mimicked surfaces can be used to recreate biological topography in an invitro model and to study drug responses to these structures. Several structures can be explored in the future to study the response of cells, and could potentially be combined with drug testing endeavours to understand how these natural surfaces influence drug effects on cells. There remains a lot of potential for collaborations with botanists to understand how the topological surfaces of different plants and flowers may influence these cellular behaviours.

“We also focus on creating affordable, efficient cell culture devices which can be used to grow 100x the number of spheroids as compared to well plates. These devices can be used to expedite the scaling-up process of cells and allow an easier way to not only grow many cells but also allow drug delivery to multiple cells at the same time” says Dr. Majumder. “This idea was also quite serendipitous; we noticed a structured polymer covering the AC ducts in our lab. Sanjay, a former student of ours used that pattern to create these microwells and now Sourav, Pankaj &Tushar are carrying the work forward.”

These low-costing microwell devices are a neat solution for high throughput organoid generation, and collaborators (Dr. Deepak Modi, NIRRH-ICMR, Mumbai) of the Majumder lab are using these devices to generate different kinds of organoids. This device could be used to speed up in-vitro drug testing and streamline drug development processes, in addition to driving down costs.

“Personal principles like keeping costs low definitely contribute to the ideas generated in this lab, but I always enjoy looking for elegant and simple solutions. We want to create solutions which can be achieved in labs worldwide, especially those from low and mid-income nations.” says Dr. Majumder. “We are eager to work with researchers from different fields and create a comprehensive network filled with collective knowledge.”

This work is funded by SERB-IMPRINT, DBT-ATGC, and Wadhwani Research Centre for Bioengineering (WRCB-IITB).

Dr. Abhijit Majumder and his team are a part of our upcoming India | EMBO Lecture Course and will be conducting a hands-on demonstration on mechanobiology and microfluidic devices. To learn more,turn to page 11.