Cryptocurrency trading platform Abra has raised $55 million in funding to bootstrap the next phase of its growth strategy, bringing several high-profile investors on board from both inside and outside the blockchain industry.  Abra will use funds from the Series C investment to grow its product offerings in wealth management, trading and payments, as well as expand its in-house capacity, the company announced Wednesday. Amex Ventures, a venture capital arm of American Express, was among the contributors alongside Blockchain Capital, Ignia, Kingsway Capital and Stellar Development Foundation. Abra has now raised over $85 million since its inception.