Date Published: March 03, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Jundong Shao, Changshun Ruan, Hanhan Xie, Zhibin Li, Huaiyu Wang, Paul K. Chu, Xue‐Feng Yu.
Photothermal therapy (PTT) is a fledgling therapeutic strategy for cancer treatment with minimal invasiveness but clinical adoption has been stifled by concerns such as insufficient biodegradability of the PTT agents and lack of an efficient delivery system. Here, black phosphorus (BP) nanosheets are incorporated with a thermosensitive hydrogel [poly(d,l‐lactide)‐poly(ethylene glycol)‐poly(d,l‐lactide) (PDLLA‐PEG‐PDLLA: PLEL)] to produce a new PTT system for postoperative treatment of cancer. The BP@PLEL hydrogel exhibits excellent near infrared (NIR) photothermal performance and a rapid NIR‐induced sol–gel transition as well as good biodegradability and biocompatibility in vitro and in vivo. Based on these merits, an in vivo PTT postoperative treatment strategy is established. Under NIR irradiation, the sprayed BP@PLEL hydrogel enables rapid gelation forming a gelled membrane on wounds and offers high PTT efficacy to eliminate residual tumor tissues after tumor removal surgery. Furthermore, the good photothermal antibacterial performance prevents infection and this efficient and biodegradable PTT system is very promising in postoperative treatment of cancer.
Surgery is the most common means to treat cancer but its success hinges on the removal of well‐defined and primary tumors located in nonvital tissue regions.1, 2, 3 Nevertheless, some forms of cancer are poorly defined with high metastasis and when they are detected from vital organs or tissues in the human body, surgery is quite challenging and may not be sufficiently effective due to the high recurrence rate after the treatment.4 To reduce the incidence of relapse, radiotherapy and chemotherapy are often implemented after surgery5 but serious complications and side effects may arise.6 In this respect, new treatment techniques besides radiotherapy and chemotherapy are desirable in clinical practice.
The BP@PLEL hydrogel is designed and adopted in a sprayable and biodegradable PTT system for postsurgical treatment of cancer. The BP@PLEL hydrogel delivers excellent NIR PTT performance, facilitates rapid sol–gel transition under NIR irradiation, and has excellent biodegradability and biocompatibility as verified by in vitro and in vivo experiments. The sprayed BP@PLEL hydrogel under NIR irradiation enables rapid gelation forming a gelled membrane on wound and has high PTT efficacy to eliminate residual tumor tissues. Compared to other previously reported PTT agents, the BP@PLEL hydrogel is especially attractive due to the biodegradability and biocompatibility. Both BP nanosheets and PLEL are biodegradable and all the degradation products are safe small molecules including phosphate, phosphonate, carbon dioxide, and water, which can be excreted harmlessly from the body after the therapy. Based on the BP@PLEL hydrogel, a new PTT treatment strategy is proposed and demonstrated by spraying only a small amount of the hydrogel onto the tumor site followed by low‐dose NIR laser irradiation (0.5 W cm−2). Compared to radiotherapy and chemotherapy, this postoperative treatment is simpler and causes less side effects. Furthermore, this technique not only eliminates residual tumor tissues, but also can prevent wound infection. It thus has immense clinical potential in the treatment of cancer.
Materials: The BP crystals were purchased from a commercial supplier (Smart‐Elements) and stored in a dark Ar glove box and N‐methyl‐2‐pyrrolidone (NMP, 99.5%, anhydrous) was obtained from Aladdin Reagents. The triblock PDLLA‐PEG‐PDLLA copolymers with a molecular weight of 4500 Da were purchased from PolySciTech (Indiana, USA). All other chemicals used in this study were analytical reagent grade and used without further purification.
The authors declare no conflict of interest.