Schematic of the preparation of hollow mesoporous carbon spheres and drug loading for cancer therapy induced by laser irradiation and assisted by microwave irradiation.Tiny particles on the micro- or nanoscale could deliver drugs, especially highly toxic anticancer drugs, in a more targeted way with fewer side effects for patients. Researchers from China have demonstrated that this approach can be given a boost by using hollow carbon spheres loaded with active agents and bombarding them with microwaves and laser irradiation simultaneously [Gui et al., Biomaterials 248 (2020) 120009, ].
Hollow structures made from sheets of carbon atoms such as fullerenes and carbon nanotubes, as well as graphene oxide (GO) and reduced GO, have all attracted interest as drug delivery systems and photothermal therapy agents. However, these materials can be toxic to cells and organisms and, in the case of graphene-based materials, require expensive and complex preparation methods using strong acids/alkalis or oxidants.
Now researchers at Tongji University and the Chinese Academy of Sciences’ Institute of Biophysics in Beijing have fabricated hollow mesoporous carbon microspheres without strong reagents that can be readily loaded with a variety of small molecule drugs. A spray of aqueous bovine serum albumin is air-dried and carbonized to produce the 5-25-µm-diameter spheres, the hollow interior of which can be filled with anticancer drugs such as doxorubicin, paclitaxel, or other active agents.
The drug-loaded microspheres are injected directly into the site of tumors to reduce the migration of active agents to other organs or tissues. As well as delivering active drugs to the tumor, the carbon microspheres convert low power laser light (from a 980-nm laser) into heat to induce a local photothermal effect. This damages the tumor by vibrating the water molecules present in the tissue. The researchers found that this effect could be enhanced markedly by simultaneously bombarding the microspheres with microwaves. While the microwaves do not interact directly with the carbon microspheres, they slightly raise the general body temperature of the test mice. This higher initial tumor temperature appears to result in an enhanced photothermal effect. As the microspheres are confined to the tumor site, only the tissue in this area experiences the enhanced photothermal effect, leaving surrounding tissue unaffected.
The combined approach shows an advantage in curbing tumor growth in mice, boosting the therapeutic effect of anticancer drugs in combination photothermal therapy without any physiological side effects. As the laser and microwave irradiation is low power, can work at a distance of several centimeters or more, and requires no specific microwave-sensitive materials, the approach easy to realize as a therapeutic strategy.
“This method is simple, safe, ‘green’, and highly efficient, and does not require organic solvents, strong acid or alkali, or strong oxidants, making it suitable for producing... porous carbon for biomedical applications in bulk,” write the researchers.