Coronavirus disease 19 (COVID-19) has occurred for more than four years, and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing COVID-19 is a strain of coronavirus, which presents high rates of morbidity around the world. Up to the present date, there are no therapeutics that can avert this form of illness, and photodynamic therapy (PDT) may be an alternative approach against SARS-CoV-2. Curcumin and methylene blue have been approved and used in clinical practices as a photosensitizer in PDT for a long time with their anti-viral properties and for disinfection through photo-inactivated SARS-CoV-2. Previously, curcumin and methylene blue with antibacterial properties have been used against Gram-positive bacteria, Staphylococcus aureus (S. aureus), and Gram-negative bacteria, Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Pseudomonas aeruginosa (P. aeruginosa). Methods: To conduct a literature review, nine electronic databases were researched, such as WanFang Data, PubMed, Science Direct, Scopus, Web of Science, Springer Link, SciFinder, and China National Knowledge Infrastructure (CNKI), without any regard to language constraints. In vitro and in vivo studies were included that evaluated the effect of PDT mediated via curcumin or methylene blue to combat bacteria and SARS-CoV-2. All eligible studies were analyzed and summarized in this review. Results: Curcumin and methylene blue inhibited the replication of SARS-CoV-2. The reactive oxygen species (ROS) are generated during the treatment of PDT with curcumin and methylene blue to prevent the attachment of SARS-CoV-2 on the ACE2 receptor and damage to the nucleic acids either DNA or RNA. It also modulates pro-inflammatory cytokines and attenuates the clotting effects of the host response. Conclusion: The photodynamic action of curcumin and methylene blue provides a possible approach against bacteria and SARS-CoV-2 infection because they act as non-toxic photosensitizers in PDT with an antibacterial effect, anti-viral properties, and disinfection functions.

Photodynamic therapy (PDT), as an alternative approach to treat tumors through reactive oxygen species (ROS) produced by the activated photosensitizers (PS) upon light irradiation, has attracted wide attention in recent years due to its low invasive and highly efficient features. However, the low hydrophilicity and poor targeting of PS limits the clinical application of PDT. Stimuli-responsive nanomaterials represent a major class of remarkable functional nanocarriers for drug delivery. In particular, tumor microenvironment-responsive nanomaterials (TMRNs) can respond to the special pathological microenvironment in tumor tissues to release the loaded drugs, that allows them to control the release of PS within tumor tissues. Recent studies have demonstrated that TMRNs can achieve the targeted release of PS at tumor sites, increase the concentration of PS in tumor tissues, and reduce side effects of PDT. Hence, in the present paper, we review TMRNs, mainly including pH-, redox-, enzymes-, and hypoxia-responsive smart nanomaterials, and focus on the application of these smart nanomaterials as targeted delivery carriers of PS in photodynamic anticancer therapy, to further boost the development of PDT in tumor therapy.

Photodynamic therapy (PDT) is a minimally invasive treatment for several diseases. It combines light energy with a photosensitizer (PS) to destroy the targeted cells or tissues. A PS itself is a non-toxic substance, but it becomes toxic to the target cells through the activation of light at a specific wavelength. There are some limitations of PDT, although it has been used in clinical studies for a long time. Two-photon excitation (TPE) and upconversion (UC) for PDT have been recently developed. A TPE nanoparticle-based PS combines the advantages of TPE and nanotechnology that has emerged as an attractive therapeutic agent for near-infrared red (NIR) light-excited PDT, whilst UC is also used for the NIR light-triggered drug release, activation of ‘caged’ imaging, or therapeutic molecules during PDT process for the diagnosis, imaging, and treatment of cancers. Methods: Nine electronic databases were searched, including WanFang Data, PubMed, Science Direct, Scopus, Web of Science, Springer Link, SciFinder, and China National Knowledge Infrastructure (CNKI), without any language constraints. TPE and UCNP were evaluated to determine if they had different effects from PDT on cancers. All eligible studies were analyzed and summarized in this review. Results: TPE-PDT and UCNP-PDT have a high cell or tissue penetration ability through the excitation of NIR light to activate PS molecules. This is much better than the conventional PDT induced by visible or ultraviolet (UV) light. These studies showed a greater PDT efficacy, which was determined by enhanced generation of reactive oxygen species (ROS) and reduced cell viability, as well as inhibited abnormal cell growth for the treatment of cancers. Conclusions: Conventional PDT involves Type I and Type II reactions for the generation of ROS in the treatment of cancer cells, but there are some limitations. Recently, TPE-PDT and UCNP-PDT have been developed to overcome these problems with the help of nanotechnology in in vitro and in vivo studies.

Summary: Astragalus is a traditional herb which has been used in China for a long time. It regulates blood circulation (vital energy), invigorates body fluid circulation, protects the flow of blood to fight against the attack of pathogens, and strengthens “blood deficiencies” according to Bencao Congxin. Astragalus was approved by the Food and Drug Administration in 2009 as a dietary supplement for upper respiratory infections, allergic rhinitis (hay fever), asthma, chronic fatigue syndrome, and chronic kidney disease. Thirty journals published in the past ten years were reviewed by using library search engines such as SCI/SCIE, PubMed, and Scopus. In this mini-review, we focus on the anti-inflammatory of Astragalus features, discuss the background of Astragalus and its function in various diseases from water-extracted Astragalus membranaceus, Astragalus saponins, and Astragalus polysaccharides. Based on the traditional Chinese medicine theory, Astragalus is a potential candidate to treat and prevent COVID-19.

Cancer is a major global health concern, affecting nearly 20 million individuals annually, according to the International Agency for Research on Cancer (IARC). There are some unconventional and conventional treatments for cancer. Typically, they span a wide spectrum of conventional and advanced therapeutic approaches, such as photodynamic therapy (PDT). This has long been valued for its non-invasive, targeted, and minimally toxic approach in the management of cancer. More importantly, PDT results in fewer operative and post-operative major complications, faster recovery times, reduced operating time, and saved costs. There are two types of photosensitizers in PDT, including synthetics (e.g., hematoporphyrin derivative, photofrin II, verteporfin) and natural (e.g., Hypocrellin A (HA) and Hypocrellin B (HB)). Nine electronic databases—WanFang Data, PubMed, ScienceDirect, Scopus, Web of Science, Springer Link, SciFinder, and the China National Knowledge Infrastructure (CNKI)—were systematically searched for this review, covering the literature published within the past 20 to 30 years (time range), without language restrictions. Studies were included if they were identified using the keywords Hypocrellin A, Hypocrellin B, photodynamic therapy, and cancer (inclusion criteria). All eligible papers were collected, critically analyzed, and summarized. Duplicate records were excluded during the screening process (exclusion criteria). HA and HB, derived from the fungus Hypocrella bambusae, offer a natural alternative with lower toxicity. However, these compounds are still in the in vitro or in vivo, and must meet rigorous standards for “quality”, “safety”, “efficacy”, “pharmacokinetics”, as well as “regulatory compliance” before entering clinical trials. “Curcumin” is a successful PS for traditional Chinese medicine used in PDT during clinical study and it is used as a benchmark for HB. Currently, scientists are paying attention to “nanotechnology” that enhances hypocrellin’s properties in PDT for achieving clinical goals, but further investigations are required.