regex_replace

index.php:

$smarty = new Smarty;
$smarty->assign('articleTitle', "Infertility unlikely to\nbe passed on, experts say.");
$smarty->display('index.tpl');

index.tpl:

{* replace each carriage return, tab & new line with a space *}

{$articleTitle}
{$articleTitle|regex_replace:"/[\r\t\n]/":" "}

OUTPUT:

Infertility unlikely to
 be passed on, experts say.
Infertility unlikely to be passed on, experts say.