Matt, who was a semi-finalist in the 2017 series of the BBC show, collapsed at the 22.5 mile mark during the race on Sunday and later died in hospital.
Campbell had hoped to raise £2,500 with his run, but the target was reached - and passed - soon after news of his death.
Matt, who reached the semi-finals of Masterchef: The Professionals previous year, was also running in memory of his dad Martin, who died in 2016. "I know you can do it!" and entered me into my first marathon; Brathay 2016 along with my brother, Josh.
A statement on London Marathon's official Twitter page, said: "With deep sadness, we confirm the death of a participant in the 2018 Virgin Money London Marathon".
"It may be in London, Somerset, Manchester - where ever you are - but if as many people can do a 3.7m run on [run tracking app] Strava on Saturday, and give a £5 "entry fee" to Matt's justgiving page, I think that'd be a nice gesture from us as a group".
Runners across the country are pledging to run 3.7 miles in memory of 29-year-old Matt Campbell, the London Marathon runner who collapsed and died before he could finish the race.
A spokesman for the Brathay Trust said: "We're not a huge charity and this is a significant sum to us, so firstly, a huge thank you to everyone who has donated - this is just fantastic".
Following his successful stint on MasterChef: The Professionals in 2017, he embarked on a United Kingdom roadshow this year - with dates in London, Manchester, Bristol and Leeds.
A spokesman for the show said: "We are shocked and saddened to hear the news about Matt Campbell, one of our talented contestants from a year ago".
In a statement, The Brathay Trust said: "Matt and his family have been tireless in supporting the work of Brathay Trust and our thoughts and prayers are with them at this awful time".