In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: RESULTS : Densitometry showed no significant difference regarding GAP43 - ir in the IML between Pilo , CHX + Pilo , and control groups .
### Output Text:
RESULTS : Densitometry showed no significant difference regarding GAP43 - ir in the IML between <span class="chemical">Pilo</span> , <span class="chemical">CHX</span> + <span class="chemical">Pilo</span> , and control groups . 