Error When Passing Quotes To Webservice By AJAX

I'm passing data using .ajax and here are my data and contentType attributes:

data: '{ "UserInput" : "' + $('#txtInput').val() + '","Options" : { "Foo1":' + bar1 + ', "Foo2":' + Bar2 + ', "Flags":"' + flags + '", "Immunity":' + immunity + '}}',
contentType: 'application/json; charset=utf-8',

Server side my code looks like this:

<WebMethod()> _
Public Shared Function ParseData(ByVal UserInput As String, ByVal Options As Options) As String

The userinput is obvious but the Options structure is like the following:

Public Structure Options
Dim Foo1 As Boolean
Dim Foo2 As Boolean
Dim Flags As String
Dim Immunity As Integer
End Structure

Everything works fine when $('#txtInput') contains no double-quotes but if they are present I get an error (for an input of asd"):

{"Message":"Invalid object passed in, u0027:u0027 or u0027}u0027 expected. (22): { "UserInput" : "asd"","Options" : { "Foo1":false, "Foo2":false, "Flags":"", "Immunity":0}}","StackTrace":" at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeDictionary(Int32 depth)
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer)
at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize[T](String input)
at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.ArgumentException"}