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: Acute doxorubicin - loaded nanoparticle ( DXNP ) renal toxicity was explored in both normal rats and rats with experimental glomerulonephritis .
### Output Text:
Acute <span class="chemical">doxorubicin</span> - loaded nanoparticle ( DXNP ) renal toxicity was explored in both normal rats and rats with experimental glomerulonephritis . 