The verb loan is one of the words English settlers brought to America and continued to use after it had died out in Britain. Its use was soon noticed by British visitors and somewhat later by the New England literati, who considered it a bit provincial. It was flatly declared wrong in 1870 by a popular commentator, who based his objection on etymology. A later scholar showed that the commentator was ignorant of Old English and thus unsound in his objection, but by then it was too late, as the condemnation had been picked up by many other commentators. Although a surprising number of critics still voice objections, loan is entirely standard as a verb. You should note that it is used only literally; lend is the verb used for figurative expressions, such as "lending a hand" or "lending enchantment."