Houston founder shares how he's using tech to make digital media more effective and equitable

houston innovators podcast episode 173

This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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Houston founder on shaping the future of medicine through biotechnology and resilience

Guest Column

Living with chronic disease has shaped my life in profound ways. My journey began in 5th grade when I was diagnosed with Scheuermann’s disease, a degenerative disc condition that kept me sidelined for an entire year. Later, I was diagnosed with hereditary neuropathy with liability to pressure palsies (HNPP), a condition that significantly impacts nerve recovery. These experiences didn’t just challenge me physically, they reshaped my perspective on healthcare — and ultimately set me on my path to entrepreneurship. What started as personal health struggles evolved into a mission to transform patient care through innovative biotechnology.

A defining part of living with these conditions was the diagnostic process. I underwent nerve tests that involved electrical shocks to my hands and arms — without anesthesia — to measure nerve activity. The pain was intense, and each test left me thinking: There has to be a better way. Even in those difficult moments, I found myself thinking about how to improve the tools and processes used in healthcare.

HNPP, in particular, has been a frustrating condition. For most people, sleeping on an arm might cause temporary numbness that disappears in an hour. For me, that same numbness can last six months. Even more debilitating is the loss of strength and fine motor skills. Living with this reality forced me to take an active role in understanding my health and seeking solutions, a mindset that would later shape my approach to leadership.

Growing up in Houston, I was surrounded by innovation. My grandfather, a pioneering urologist, was among the first to introduce kidney dialysis in the city in the 1950s. His dedication to advancing patient care initially inspired me to pursue medicine. Though my path eventually led me to healthcare administration and eventually biotech, his influence instilled in me a lifelong commitment to medicine and making a difference.

Houston’s thriving medical and entrepreneurial ecosystems played a critical role in my journey. The city’s culture of innovation and collaboration provided opportunities to explore solutions to unmet medical needs. When I transitioned from healthcare administration to founding biotech companies, I drew on the same resilience I had developed while managing my own health challenges.

My experience with chronic disease also shaped my leadership philosophy. Rather than accepting diagnoses passively, I took a proactive approach questioning assumptions, collaborating with experts, and seeking new solutions. These same principles now guide decision-making at FibroBiologics, where we are committed to developing groundbreaking therapies that go beyond symptom management to address the root causes of disease.

The resilience I built through my health struggles has been invaluable in navigating business challenges. While my early career in healthcare administration provided industry insights, launching and leading companies required the same determination I had relied on in my personal health journey.

I believe the future of healthcare lies in curative treatments, not just symptom management. Fibroblast cells hold the promise of engaging the body’s own healing processes — the most powerful cure for chronic diseases. Cell therapy represents both a scientific breakthrough and a significant business opportunity, one that has the potential to improve patient outcomes while reducing long-term healthcare costs.

Innovation in medicine isn’t just about technology; it’s about reimagining what’s possible. The future of healthcare is being written today. At FibroBiologics, our mission is driven by more than just financial success. We are focused on making a meaningful impact on patients’ lives, and this purpose-driven approach helps attract talent, engage stakeholders, and differentiate in the marketplace. Aligning business goals with patient needs isn’t just the right thing to do, it’s a powerful model for sustainable growth and lasting innovation in biotech.

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Pete O’Heeron is the CEO and founder of FibroBiologics, a Houston-based regenerative medicine company.


Houston researchers make headway on affordable, sustainable sodium-ion battery

Energy Solutions

A new study by researchers from Rice University’s Department of Materials Science and NanoEngineering, Baylor University and the Indian Institute of Science Education and Research Thiruvananthapuram has introduced a solution that could help develop more affordable and sustainable sodium-ion batteries.

The findings were recently published in the journal Advanced Functional Materials.

The team worked with tiny cone- and disc-shaped carbon materials from oil and gas industry byproducts with a pure graphitic structure. The forms allow for more efficient energy storage with larger sodium and potassium ions, which is a challenge for anodes in battery research. Sodium and potassium are more widely available and cheaper than lithium.

“For years, we’ve known that sodium and potassium are attractive alternatives to lithium,” Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Engineering at Rice, said in a news release. “But the challenge has always been finding carbon-based anode materials that can store these larger ions efficiently.”

Lithium-ion batteries traditionally rely on graphite as an anode material. However, traditional graphite structures cannot efficiently store sodium or potassium energy, since the atoms are too big and interactions become too complex to slide in and out of graphite’s layers. The cone and disc structures “offer curvature and spacing that welcome sodium and potassium ions without the need for chemical doping (the process of intentionally adding small amounts of specific atoms or molecules to change its properties) or other artificial modifications,” according to the study.

“This is one of the first clear demonstrations of sodium-ion intercalation in pure graphitic materials with such stability,” Atin Pramanik, first author of the study and a postdoctoral associate in Ajayan’s lab, said in the release. “It challenges the belief that pure graphite can’t work with sodium.”

In lab tests, the carbon cones and discs stored about 230 milliamp-hours of charge per gram (mAh/g) by using sodium ions. They still held 151 mAh/g even after 2,000 fast charging cycles. They also worked with potassium-ion batteries.

“We believe this discovery opens up a new design space for battery anodes,” Ajayan added in the release. “Instead of changing the chemistry, we’re changing the shape, and that’s proving to be just as interesting.”

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This story originally appeared on EnergyCapitalHTX.com.

FAA demands investigation into SpaceX's out-of-control Starship flight

Out of this world

The Federal Aviation Administration is demanding an accident investigation into the out-of-control Starship flight by SpaceX on May 27.

Tuesday's test flight from Texas lasted longer than the previous two failed demos of the world's biggest and most powerful rocket, which ended in flames over the Atlantic. The latest spacecraft made it halfway around the world to the Indian Ocean, but not before going into a spin and breaking apart.

The FAA said Friday that no injuries or public damage were reported.

The first-stage booster — recycled from an earlier flight — also burst apart while descending over the Gulf of Mexico. But that was the result of deliberately extreme testing approved by the FAA in advance.

All wreckage from both sections of the 403-foot (123-meter) rocket came down within the designated hazard zones, according to the FAA.

The FAA will oversee SpaceX's investigation, which is required before another Starship can launch.

CEO Elon Musk said he wants to pick up the pace of Starship test flights, with the ultimate goal of launching them to Mars. NASA needs Starship as the means of landing astronauts on the moon in the next few years.

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