By Suherman Candra Maholtra 
In a significant advancement for preventative dermatology and materials science, researchers at the University of California, Los Angeles (UCLA) have developed a novel mineral sunscreen formulation that addresses one of the most persistent barriers to daily sun protection: the unsightly, chalky white residue known as "white cast." The study, led by a multidisciplinary team at the UCLA Health Jonsson Comprehensive Cancer Center, demonstrates that by altering the physical architecture of zinc oxide particles from traditional spheres into microscopic four-armed structures called tetrapods, scientists can create a high-performance sunscreen that is aesthetically inclusive for all skin tones without compromising on ultraviolet (UV) protection.
The research, recently published in the journal ACS Materials Letters, arrives at a critical time for public health. Skin cancer remains the most frequently diagnosed malignancy in the United States, with over five million cases treated annually. While dermatologists have long advocated for the daily application of sunscreen to mitigate the DNA-damaging effects of UV radiation, consumer compliance remains low. A primary deterrent for many users, particularly those with darker skin tones, is the visible film left by mineral-based blockers. By solving this aesthetic dilemma through structural engineering rather than chemical additives, the UCLA team has opened a new pathway for increasing sunscreen adherence and reducing the national burden of skin disease.
The Public Health Context: Skin Cancer and the Compliance Gap
The necessity for effective, wearable sun protection is underscored by sobering clinical data. According to the American Academy of Dermatology, one in five Americans will develop skin cancer in their lifetime. Ultraviolet radiation from the sun—specifically UVA rays, which penetrate deeply to cause premature aging and long-term DNA damage, and UVB rays, which cause immediate sunburns—is the primary environmental catalyst for these conditions.
Despite the widespread availability of sunscreens, a significant portion of the population does not use them correctly or consistently. For many, the choice of sunscreen involves a trade-off between chemical and mineral filters. Chemical sunscreens (containing ingredients like oxybenzone or avobenzone) absorb UV radiation but have faced scrutiny regarding their environmental impact on coral reefs and potential systemic absorption in humans. Conversely, mineral sunscreens, which utilize zinc oxide or titanium dioxide, work by reflecting and scattering UV light. These are classified by the U.S. Food and Drug Administration (FDA) as "generally recognized as safe and effective" (GRASE).
However, mineral sunscreens are notoriously difficult to formulate for aesthetic appeal. Traditional zinc oxide particles are roughly spherical and tend to clump together—a process known as aggregation. When these clusters reach a certain size, they scatter visible light, creating a white or grayish appearance on the skin. This "white cast" is not merely a cosmetic annoyance; it is a health equity issue. For individuals with higher melanin content, the residue is starkly visible, often leading to the abandonment of sun protection altogether.
Engineering the Solution: From Nanospheres to Tetrapods
The breakthrough achieved by the UCLA team, led by chemical biology doctoral candidate AJ Addae and senior author Paul S. Weiss, lies in the application of materials science to cosmetic chemistry. Rather than seeking a new chemical compound, the researchers focused on the morphology of existing zinc oxide.
Standard zinc oxide used in the industry typically consists of nanoparticles produced via wet-chemical methods, which yield small, round shapes that pack tightly together. The UCLA study utilized a patented high-temperature flame synthesis process to create zinc oxide tetrapods. These structures feature a central core with four protruding "arms" or spikes.
"Because of their structure, these tetrapod-shaped particles have standoffs and form porous networks instead of collapsing into clumps," explained Addae, who is also a cosmetic science entrepreneur. "They can’t pack tightly and aggregate, so they stay evenly distributed in the sunscreen."
The geometric properties of the tetrapods prevent the particles from forming the large, light-scattering clusters responsible for the white cast. In laboratory settings, the tetrapod-based lotions demonstrated a "warmer" appearance on the skin, effectively blending into various complexions without the need for added pigments or artificial tints. This structural stability also means the sunscreen is less likely to separate in the bottle or become excessively viscous over time, improving the overall shelf-life and user experience.
Performance and Stability Data
To validate the efficacy of the new structure, the researchers conducted a series of comparative tests between tetrapod-shaped zinc oxide and conventional spherical nanoparticles. The results indicated that the tetrapod formulation provided robust protection that met industry standards.
- Sun Protection Factor (SPF): When tested at equivalent concentrations, the tetrapod formula achieved an SPF of approximately 30. This level of protection is widely recommended by dermatologists for daily use to prevent both non-melanoma skin cancers and melanoma.
- UVA/UVB Balance: The tetrapod structures maintained the broad-spectrum capabilities inherent to zinc oxide, effectively blocking the full range of damaging radiation.
- Rheological Stability: The study found that the tetrapod sunscreen maintained a more consistent texture. Traditional mineral sunscreens often require heavy shaking to redistribute settled particles; the tetrapod network remained suspended, ensuring that every application provides a uniform dose of active ingredients.
- Visual Transparency: Using controlled applications on various skin types, the researchers observed a significant reduction in light scattering. The tetrapod particles allowed more natural skin pigment to show through while still providing a physical barrier against UV rays.
Addressing Health Disparities in Dermatology
One of the most profound implications of this research is its potential to improve health outcomes for people of color. While the incidence of melanoma is lower in Black, Hispanic, and Asian populations compared to White populations, the mortality rates are often higher among people of color.
Data from the American Cancer Society suggests that Black patients are more likely to be diagnosed with melanoma at a late stage, when the five-year survival rate drops significantly. One contributing factor is the misconception that darker skin does not require sun protection, compounded by a lack of products designed for diverse skin tones.
"I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin," said Addae. "That frustration really became the starting point for this work. If we can make zinc oxide look better on more skin tones without sacrificing protection, it could help more people protect themselves from the sun’s most dangerous effects."
By removing the "aesthetic tax" of mineral sunscreen, the researchers hope to encourage higher rates of daily application in communities that have historically been underserved by the sun-care industry.
The Research Team and Collaborative Effort
The success of the project is attributed to a unique collaboration between chemistry, bioengineering, and clinical dermatology. Senior author Paul S. Weiss, a distinguished professor at UCLA and an investigator at the UCLA Health Jonsson Comprehensive Cancer Center, emphasized that the project represents the "best of interdisciplinary science."
The team also included Jennifer Uyanga, professor Justin Carman of UCLA’s department of chemistry and biochemistry, and professor Yogendra Kumar Mishra of the University of Southern Denmark. The inclusion of international expertise in flame-based materials synthesis was vital for producing the specialized tetrapod structures at the necessary scale for testing.
The project received support from several prestigious institutions, including the National Science Foundation (NSF), the Challenge Initiative at UCLA, and a Sigma Xi IFoRE Grant-in-Aid. This funding underscores the recognition of sun protection as a vital area of public health research.
Future Directions and Clinical Trials
While the initial results are promising, the UCLA team is preparing for the next phases of development required to bring the technology to the consumer market. A critical area of focus is the interaction between the tetrapod particles and the skin microbiome—the delicate ecosystem of bacteria and fungi that live on the skin’s surface.
"We are now collaborating with the UCLA Health department of dermatology, including UCLA Health’s Skin of Color Clinic," Weiss noted. "We want to ensure that these new structures are not only aesthetically superior but also maintain the high safety profile that mineral sunscreens are known for."
Future studies will involve human clinical trials to assess the long-term wearability, water resistance, and potential for skin irritation. Additionally, the researchers are exploring how the tetrapod shape might allow for even higher SPF ratings without increasing the concentration of zinc oxide, potentially leading to even lighter and more comfortable formulations.
Conclusion: A New Standard for Sun Care
The work coming out of UCLA suggests that the future of sun protection lies in the precise control of matter at the microscopic level. By moving away from simple spheres and toward more complex, engineered structures like tetrapods, the researchers have addressed a decades-old complaint that has hindered skin cancer prevention efforts.
"This isn’t just about cosmetics," Professor Weiss concluded. "If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention."
As the skincare industry continues to evolve toward "cleaner" and more environmentally friendly ingredients, the demand for high-quality mineral sunscreens is expected to grow. The UCLA tetrapod technology provides a blueprint for how science can bridge the gap between safety, efficacy, and inclusivity, ensuring that the "best sunscreen"—the one that people actually use—is available to everyone, regardless of their skin tone.
