Targeted Photodynamic Therapy of Oral Bacteria Using Antibody-Conjugated Nanoparticles

Objectives: While targeting of biofilm bacteria and sparing of eukaryotic cells is possible through drug dosimetry, it is also preferable to target the disease-causing organisms within plaque specifically, and thus promote the maintenance of a healthy plaque. To achieve this we employed antibody-conjugated gold nanoparticles.

Methods: Gold nanoparticles were synthesised to which had been conjugated erythrosine and antibody specific to either S. mutans or L. casei. These conjugates were designated S.m.-G-Er and L.c.-G-Er respectively. The conjugates were then used for the PDT of mixed 2 species biofilm cultures of S. mutans and L. casei grown in a constant depth film fermenter. Cell killing was determined by colony counting.

Results: The results showed that specific nanoparticles caused killing of their target organism in both a light and drug-dependent manner. Up to 2 log₁₀ of cell kill of L. casei was achieved using L.c.-G-Er and 1.5 log₁₀ killing of S. mutans when using S.m.-G-Er. Little cross-reactivity to the non-target organism was observed with either type of nanoparticle.

Conclusion: Specific killing of target organisms was achieved using targeted nanoparticles. The use of antibody and erythrosine-labelled nanoparticles shows potential for the targeting of specific bacterial species in oral plaque biofilms.