# A Biomimetic Buffering Hydrogel Scaffold for Long‐Term Culture of Patient‐Derived Tumor Organoids

## TL;DR

A new hydrogel scaffold helps maintain the right pH for long-term cancer organoid growth, mimicking the tumor environment better.

## Contribution

A biomimetic hydrogel with built-in buffering capacity is introduced to maintain physiological pH during organoid culture.

## Key findings

- The hydrogel maintained pH in the physiologically relevant range during long-term culture.
- The hydrogel preserved its structural and mechanical properties over 21 days.
- Cancer cell proliferation was enhanced in organoids cultured in the buffering hydrogel.

## Abstract

Patient‐derived cancer organoids have emerged as a promising in vitro model for fundamental cancer research and drug screening for therapeutic cancer treatment. Yet, while the inherent acidification of the tumor environment in vivo is controlled at a particular level, hydrogel scaffolds used for organoid culture lack this ability and their pH falls outside the physiologically relevant range. The excessive acidification can also lead to the degradation of pH‐sensitive hydrogel scaffolds during long‐term organoid culture, thus changing the mechanical properties of the organoid microenvironment. Here, we report a biomimetic fibrous hydrogel with built‐in buffering capacity, which enables control of the local acidification of the organoid environment to maintain its mechanical and structural stability. The hydrogel is formed from aldehyde‐functionalized cellulose nanocrystals carrying histidine buffering molecules, and gelatin. During long‐term organoid culture, the hydrogel maintained the pH in the physiologically relevant range, while maintaining network integrity and mechanical properties. The organoids grown in this hydrogel exhibited enhanced proliferative activity of cancer cells, thus reflecting a more homeostatic tumor‐like niche. This work shows that introducing a buffering functionality into the hydrogel scaffold enables significantly improved support for long‐term culture of patient‐derived breast cancer organoids under physiologically relevant conditions.

A biomimetic fibrous buffering hydrogel controls the local acidification at the tumoroid/hydrogel interface at the physiologically relevant level over 21‐day culture. The buffering effect promotes cancer cell proliferation in the tumoroids and supports the structural integrity and mechanical properties of the hydrogel scaffold over long‐term tumoroid growth.