There aren’t many scientists whose influence radiates so widely that millions benefit from their work without ever hearing their name. Yet that is precisely the impact Professor Tayyaba Hasan has had on the world.

Born into a Muslim family in Pratapgarh, India, she has lived all over Pakistan, and moved to America for her PhD. Over the past five decades, she has mentored hundreds of scientists. Her former students and postdocs are now scattered across the globe in what we call the “Hasan diaspora”.

I have known Prof. Hasan since 2009 where we met formally at the 12th World Congress of the International Photodynamic Association in Seattle, Washington. We have been working together on the IPA Board for over the past decade to witness firsthand what a formidable force she is for bringing economical photodynamic therapies (PDT) to global healthcare systems through science and clinical excellence.

As friends, colleagues, mentees, and admirers gathered in Cambridge, Massachusetts, to celebrate her 80th birthday in November 2025, what became clear was that the accolades tell only part of the story and don’t explain why a roomful of people from across the world came to honour her.

To me, Prof. Hasan is not only a scientist, but a friend. To many of us, she is far more than a pioneer of photodynamic therapy. She is its anchor, its matriarch — our “Mother of PDT.”

The Maternal Force

If you’ve ever worked with Prof. Hasan, you know she embodies the spirit of a “Tiger Mom”. Not in the clichéd sense, but in the way she nurtures ideas, people, and technologies with fierce loyalty and endless patience.

So many breakthroughs in PDT, including Visudyne, which brought light-activated therapy to millions, bear her fingerprints. Millions have benefited from light-activated therapies because Prof. Hasan fought for the technologies long before the medical mainstream embraced them.

Prof. Hasan’s influence reaches into the work my team and I have pursued at Canada’s Ondine Biomedical, where antimicrobial PDT therapies have now helped hundreds of thousands of patients avoid hospital infections. Prof. Hasan’s foundational science and her steady encouragement have been constant sources of strength. I often think of her not only as a scientific trailblazer, but as someone who made it personally possible for many of us to keep pursuing the promise of light. This is Nobel-worthy work.

She has nurtured not just ideas, but people. Scientists, clinicians, innovators, and leaders, whom she guided, filled a conference room for her 80th birthday celebrations, in November 2025 followed by dinner at an Indian restaurant in Cambridge.

Prof. Hasan’s science gave them the foundation, and her belief in them gave them the courage. Her work is generational, creating not only new discoveries, but new discoverers.

Unshakeable Architect

Beyond the bench, Prof. Hasan has shown equally impressive tenacity in holding together the International Photodynamic Association. For four decades, along with friends like scientists David Kessel, Colin Hopper, Brian Wilson, Brian Pogue, and others, she sustained and grew what once felt like a small, fragile community.

Today, that community spans continents, with the 19th biennial meeting held in Shanghai, June 2025, showcasing extraordinary global talent.

Prof. Hasan believes that light-based therapies can reach their full potential only if the people behind them trust one another. Much of the camaraderie we now take for granted in the PDT world — what I often call “the speed of trust”— flows directly from her influence.

The “Hasan diaspora” has become an informal, organic network providing expertise, mentorship, and support wherever PDT research and commercialization encounter new challenges. It’s a global village she quietly — and sometimes not so quietly — raised.

Prof. Hasan’s guidance is memorable to everyone she has mentored. She didn’t just teach PDT; she taught conviction, resilience, and ambition.

I’ve seen her treated like a rock star at world congresses — surrounded by students who simply wanted a few minutes of her time. I used to joke that being around her felt like being a roadie for a celebrity.

And yet, beneath all that deserved reverence, she remains profoundly human, generous, and thoughtful, never too busy to check in when life becomes difficult. Some of my favorite memories of her are not from conference halls but from quiet walks in Vancouver or conversations in the mountains of Whistler, British Columbia.

Long may Prof. Hasan continue to shape PDT research, mentor newcomers, and inspire us with new ideas. But if she decides it’s time to slow down, spend more days in the garden, or simply enjoy life’s quieter pleasures, she has more than earned that peace.

Her influence is so vast that it will continue to illuminate the field long after she chooses to rest. In my view, it is this global PDT network, in time, will prove to be her greatest legacy.

(The author is chief executive officer for Ondine Biomedical Inc., Vancouver, Canada. This article is adapted from her speech at Prof. Hasan’s birthday dinner in Cambridge, Massachusetts, on 8 November. By special arrangement with Sapan)