Sitecore's solution is correct. It looks like you are getting escape characters in your strings. If you want to exclude all characters that are not alphanumeric or ':' you can use the Regex class like this
string testString = "\"status\":\"ok\"";
var regex = new Regex("[^a-zA-Z0-9 :]");
string cleanedString = regex.Replace(testString, "");
Console.WriteLine(cleanedString);
Console.ReadLine();
What it is doing is matching all characters that are not a-z,A-Z,0-9 or : and replacing each with an empty string.