"It was pretty overwhelming to get that sort of response in such a short period of time," he said. "We definitely knew there was interest from investors but to get that level was really encouraging."
Designer Wardrobe has previously focused on womenswear with Brooke saying the capital would be used to expand into menswear and kidswear, as well as funding expansion into Australia which had been on the cards for a while.
Users can already rent clothes from other users on the platform, but Brooke said she planned to build the company's own rental portfolio with some of the money being used to buy rental stock.
"As a fashion-tech company, the capital will be used to continue to create an even bigger and better peer-to-peer experience for our much loved members," Brooke said.
"We're going to stick with what our customers love, which is some of the [usual] designer brands but then we'll also look into some higher end things like Gucci for example."
Brooke founded Designer Wardrobe in 2013, originally through Facebook, as a way to pay rent after being diagnosed with thyroid cancer.
The page amassed several thousand followers in the first few weeks, eventually prompting Brooke to set up a business platform after recovering from her illness.
"I'd always wished there was something like Designer Wardrobe and I needed to sell all my clothes because I had no money and I was unwell," Brooke said.
"So I just got on and did it and within a few weeks we had thousands of people on it. It was a great project to have going and to keep my mind positive at that time."
The platform now has a growing customer base of more than 87,000 members with more than 26,000 listings and about 1.2 million page views per month.
Designer Wardrobe also has a key backer in Spark chief executive Simon Moutter - one of the early investors and chairman of the company.
"I love the concept and the way it creates significant value for buyers and sellers of fashion," Moutter said. "Donielle and Aidan really inspire me as young, passionate entrepreneurs and I jumped at the chance to get involved."
The maximum equity on offer is 29.8 per cent based on a pre-money valuation of $4m.
The offer closes on June 15.