Using ultrasound and photoacoustics to monitor in situ forming implant structure and drug release

Most chemotherapeutics (CTs) are delivered systemically, causing nausea, hair loss, fatigue and a compromised immune system. Biocompatible in situ forming implants (ISFIs) are drug delivery vehicles which are injected as a liquid before solidifying in tissues and ultimately breaking down. By dissolving CTs in an ISFI solution, they can be injected directly to the tumour site and released in a controllable manner. ISFIs can provide localized, continuous release of CT, reducing side effects. The complex phase change of ISFIs cause variable release rate of CT. For the first time, photoacoustic (PA) imaging was used to monitor a dye (mimicking CT) diffusing into a tissue mimicking phantom while quantitative ultrasound (QUS) was used to monitor the changes in the ISFI structure.