Sustainability-focused non-fungible token (NFT) platform OneOf has raised $8.4 million in a strategic funding round that included Amex Ventures, the venture capital arm of American Express. The credit card company will host an exclusive pop-up event that includes OneOf NFTs, according to a press release provided to CoinDesk.

Other investors included Mirabaud Lifestyle Impact and Innovation fund, Snow Hill Partners, Sangha Capital and Chain Link Crypto Fund, among others.

Miami-based OneOf built its platform on the energy-efficient Tezos and Polygon blockchains, which offer low transaction fees. Founded in 2021, OneOf has signed partnerships with the estate of late rap legend Biggie Smalls, hockey great Wayne Gretzky and the Grammy Awards, to name a few. The startup has raised more than $72 million in total funding, including a $63 million seed round in May 2021.

American Express will host a color-theory and therapy-focused event, the American Express Summer in Color Oasis at the Mandarin Oriental hotel in Bodrum, Turkey. Card members who attend will receive a free OneOf NFT designed by Turkish artist Selay Karasu. The pop-up started Friday and runs through Aug. 21.

“A growing number of creators and consumer brands are experimenting with NFTs leading to the rise of a new spend category, new business ideas and new loyalty and membership models,” Amex Ventures’ managing director, Margaret Lim, said in the press release. “We believe that the investment in OneOf will help American Express stay close to the developments in NFT-powered commerce and lead to the development of new customer engagement models for our Card Members.”