An official website of the United States government
Here's how you know
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
The principle of photodynamic diagnosis (PDD) of 5-ALA mediated protoporphyrin IX (PpIX) in tumour cells (a); molecular structure of PpIX and fluorescence spectrum (b), following excitation with violet blue light at 405 nm, PpIX emits a red fluorescence of 635 nm.