what is alternative of mysql_real_escape_string in wordpress ?

$arr=				array( 
				'subject' => $subject,
				'message' =>  $message,
				'department' =>  mysql_real_escape_string($department),
   
				) ;	
			$insert=$wpdb->insert( 
				"{$wpdb->prefix}ticket", 
				$arr
			);
		 

Warning: mysql_real_escape_string(): Access denied for user ''@'localhost' (using password: NO 

Warning: mysql_real_escape_string(): A link to the server could not be established 

$wpdb->escape($input);