Thermoreversible Polymers with Improved Stability and Methods and Uses Thereof PEG-PNIPAAM Hydrogels for Scalable Stem Cell Differentiation

This patent covers a family of thermoreversible PEG and poly(N-isopropylacrylamide) hydrogels engineered for scalable culture and differentiation of human pluripotent stem cells, with applications including the production of inhibitory GABAergic cortical interneurons, midbrain dopaminergic neurons, pancreatic endoderm progenitor cells, and haematopoietic stem cells.

The Problem

Human pluripotent stem cells (hPSCs) can in principle differentiate into any cell type in the body, but the practical promise of stem cell therapies has been gated by the difficulty of producing relevant cells at clinically useful scale. Two-dimensional culture systems on plastic dishes cannot economically generate the billions of cells needed for a single patient dose. Three-dimensional bioreactor culture requires hydrogels that support cell expansion and differentiation without leaching, without xenogeneic components such as Matrigel, and without shear damage when cells are loaded or released. Existing thermoresponsive polymers like poly(N-isopropylacrylamide) (PNIPAAM) reversibly transition from liquid below their lower critical solution temperature (LCST) to gel above it, which sounds ideal, but the practical formulations available have stability issues over the weeks-long differentiation runs that sensitive neuronal and pancreatic protocols need, and their viscosity profile makes them difficult to load into commercial liquid handling and microfluidic encapsulation systems.

What This Invention Does

The invention provides a class of thermoreversible polymers described by Formula III, a PEG and PNIPAAM copolymer with specified mole fractions of comonomers, defined PEG length, total molecular weight above 50 kDa, and a w/w ratio of PEG to PNIPAAM copolymer backbone above 1:2. The polymer is made by polymerising N-isopropylacrylamide, alkyl methacrylate, and N-acryloxysuccinimide in a single solvent, conjugating with a mono-PEG-amine, then reacting with isopropylamine to finish. The resulting hydrogel has a lower critical solution temperature of about 12 to 32 degrees Celsius (preferably about 22 degrees), a stiffness of approximately 100 to 8000 Pa (preferably 800 to 1000 Pa), and a liquid-phase viscosity of about 200 to 4000 cP (preferably 200 to 1000 cP). The patent also claims an in vitro method using the hydrogel to produce a cell population enriched for inhibitory GABAergic cortical interneurons from human pluripotent stem cells, xeno-free and free of extracellular matrix protein additives, and a composition comprising the resulting cell population. The application is a divisional of AU 2024343386, claiming priority from US provisionals 63/595,847 and 63/595,841 filed 3 November 2023.

Key Features

• Defined polymer chemistry. Formula III specifies a PEG and PNIPAAM copolymer with explicit mole fraction, molecular weight, and PEG-to-PNIPAAM ratio constraints, supporting a discoverable composition space for variants and reproducible manufacture.
• LCST tuned for cell culture. With a lower critical solution temperature near 22 degrees Celsius, the polymer is a low-viscosity liquid at room-temperature loading and gels at 37 degrees Celsius incubator conditions, enabling cell encapsulation in standard liquid-handling and microfluidic systems.
• Stability across long differentiation runs. The molecular weight and PEG length are selected to keep the hydrogel structurally stable through the multi-week protocols required for neuronal and pancreatic differentiation, addressing a key failure mode of earlier thermoresponsive systems.
• Xeno-free and ECM-free. The hydrogel is designed to work without animal-derived components or extracellular matrix proteins such as Matrigel, removing a major regulatory and reproducibility issue in clinical-grade cell manufacture.
• Cortical interneuron application. The patent specifically claims an in vitro method using the hydrogel to produce post-mitotic inhibitory GABAergic cortical interneurons enriched populations, addressing a cell type relevant to epilepsy and schizophrenia cell therapy programs.

Who Is Behind It?

The applicant is Axent Biosciences Inc., a stem cell therapeutics company developing scalable manufacturing platforms for pluripotent stem cell derived therapies. The named inventors are Rocio G. Sampayo and Hunter J. Johnson. The Australian patent attorney is RnB IP in Deakin, ACT. The application is a divisional of AU 2024343386, claiming priority from US provisionals 63/595,847 and 63/595,841 filed 3 November 2023.

Why It Matters

The cell therapy field is in a manufacturing pivot. Approved CAR-T products and pipeline cell therapies for Parkinson’s disease (midbrain dopaminergic neurons), epilepsy (GABAergic cortical interneurons), type 1 diabetes (pancreatic islet cells), and blood disorders (HSCs) all need cell manufacturing at orders of magnitude greater scale than the current academic and biotech infrastructure can deliver economically. Australia has growing strength in stem cell research through the Australian Regenerative Medicine Institute and Stem Cells Australia, and in cell manufacturing through Cell Therapies (Peter Mac). A patented polymer scaffold that supports xeno-free, scalable, multi-lineage differentiation is the kind of upstream IP that underlies many downstream cell therapy products and may be the subject of licensing or supply agreements with both global cell therapy companies and Australian manufacturing partners.

Related Concepts

This application sits within the broader field of regenerative medicine, where engineered biomaterials and tissue engineering approaches aim to grow patient-ready cells outside the body and deliver them as therapies.

Thermoresponsive polymers like PNIPAAM rely on a lower critical solution temperature phase transition to switch between liquid and gel, making them attractive scaffolds for cell culture and downstream stem cell therapies for diseases such as Parkinson’s disease, epilepsy, and type 1 diabetes.

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AU 2026201865 was published in the Australian Official Journal of Patents on 2 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.