Bill Gates Funds 'SLIM' Microneedle Tech That Self-Assembles Inside the Body

Long-acting contraceptive delivered through self-aggregating, long-acting injectable microcrystals (SLIM) that form an implant inside the recipient’s body after injection.

A new injectable contraceptive platform developed with Gates Foundation funding is being promoted as a “nonsurgical option for women,” but its self-assembling drug delivery mechanism and potential for future adaptation to neuropsychiatric and infectious disease drugs raise serious safety, ethical, and biosecurity concerns.

Bill Gates supports depopulation, during a 2010 TedTalk stating that “if we do a really great job on new vaccines, health care, reproductive health services, we could lower [the world population] by, perhaps, 10 or 15 percent.”

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The new technology, described in Nature Chemical Engineering and reported by Healio yesterday, was developed by researchers from MIT, Harvard Medical School, and the Broad Institute.

It delivers the long-acting contraceptive levonorgestrel through self-aggregating long-acting injectable microcrystals, or “SLIM,” that form an implant inside the recipient’s body after injection.

“Once injected, the drug microcrystals self-aggregate in the subcutaneous space to form a monolithic implant,” said Giovanni Traverso, MD, BChir, PhD, associate professor at MIT and physician at Harvard Medical School.

In a press release, the researchers described the mechanism as “like tiny puzzle pieces that, once injected inside the body, undergo solvent exchange to assemble into a single solid implant that slowly releases the drug as the surface erodes.”

This solvent-exchange crystallization process, enabling administration with an ultra-thin 30-gauge needle, allows for “prolonged drug release” without requiring surgery.

It bypasses traditional medical oversight and dramatically increases the possibility of self-administration, which researchers claim would improve accessibility and “medication use.”

But this radical convenience comes at a cost.

Traverso explained the driving motivation behind the project:

“The challenge is people do not like injections. Is there a way to engineer something to help overcome those types of challenges? That is our focus.”

Their solution was to use a solvent that solubilizes the drug during injection, then “go[es] away” in the body, leaving behind the crystallized drug structure.

“What we were able to figure out is by using a solvent or fluid that can help solubilize the drug, we could load that solution in a way that, when injected, that solvent would go away and leave behind that solid depot of drug,” Traverso told Healio. “Because it is fluid and we are loading it, it is much easier to inject. That was critical.”

“We also wanted that object to be solid enough that we could retrieve it if we needed to.”

The goal, he said, was a drug platform that could be injected easily yet form a physically solid implant that may be removable if required—though the method of removal post-aggregation is unclear.

According to Healio, “the solvent-exchange-mediated aggregation mechanism allows injections through needles as small as 30 G with no polymer and 25 G with a small amount of polymer while extending the drug release time frame.”

Histological studies allegedly confirmed the drug platform was “well tolerated,” and researchers claim its applications could extend beyond contraception.

“Specifically, in applications such as contraception, SLIM’s capability for prolonged drug release could significantly reduce the frequency of administration compared with current self-administrable options such as Depo-Provera and Sayana Press,” the researchers wrote.

But they don’t intend to stop at contraceptives.

“Traverso said the researchers are still actively working on the platform and applying it to several other infectious and neuropsychiatric conditions.”

“From a manufacturing standpoint, this [design] is simple and low cost,” Traverso said. “This work was funded by the Gates Foundation, an organization that considers those aspects from an early stage.”

He concluded:

“We hope to be in humans [with this technology] within the next 3 to 5 years, assuming further funding.”

What This Means

The Gates Foundation is now backing a self-assembling drug delivery platform designed for low-cost mass production, self-injection, and potential fertility suppression—and the developers plan to expand its use to psychiatric drugs and vaccines.

The key concerns:

• The “solid depot of drug” is formed inside the body via solvent-triggered crystallization.

• There is no clear long-term data on biocompatibility, systemic toxicity, or removal protocols.

• It circumvents surgical protocols and facilitates self-injection with minimal oversight.

• The same platform may be repurposed for behavior-modifying psychiatric agents or bioengineered therapeutics.

For now, it’s branded as an “accessible” form of birth control.

But the underlying platform is being actively refined for mass delivery of other potent drugs—with Gates Foundation support, MIT engineering, and Broad Institute backing.

The same institutions that partnered on controversial COVID-19 vaccine research are now developing bio-integrated implants that form themselves once inside your body.

And they want to inject it into humans by 2028.

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