Nonfungible token protocol Alethea AI has closed a $16 million private token sale to build scalable infrastructure for the NFT market, highlighting once again the growing demand for digital collectibles.

Billionaire investor Mark Cuban was among the backers of the Alethea AI token sale, which was co-led by Metapurse and Capital. Some of blockchain’s biggest venture funds participated in the sale, including Alameda Research, Multicoin, Galaxy Interactive, Dapper Labs, LD Capital, Gemini Frontier Fund, Borderless Capital and others. Individual investors included CoinShares’ Meltem Demirors and Haseeb Qureshi of Dragonfly Capital.

The funding will go towards building “scalable AI infrastructure for NFTs” that will give digital collectibles more dynamic characteristics, Alethea AI said. The company has been working closely with Open AI to develop its underlying technology. Once complete, Alethea’s protocol will enable NFTs to become “interactive media assets, with personality traits, preferences and real-time interactive capability.”

After a historic run-up in the first half of the year, NFT mania is showing little sign of abating. The latest craze appears to be centered around Ethereum Pet Rocks, which are selling for record amounts. According to industry sources, EtherRock #61 sold for 78 ETH on Aug. 11, which was equivalent to $250,000 at the time. The most expensive EtherRock is reportedly going for $1.9 billion.

Earlier this month, NFT platform OpenSea announced that its gross market volume for the year surpassed $1 billion for the first time. By comparison, the platform generated $24 million in gross volume in all of 2020 and $8 million in 2019. As far as NFT sales go, more than $2.5 billion worth of transactions were recorded through the first six months of 2021.

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Venture funds are also backing NFT protocols and platforms with greater conviction. As Cointelegraph reported, several major investors including Pantera, Coinbase Ventures and Sony recently backed a $30 million Series A funding round for MakersPlace.