Development of Platinum Complexes for Tumor Chemoimmunotherapy.

Platinum complexes are potential antitumor drugs in chemotherapy. Their impact on tumor treatment could be greatly strengthened by combining with immunotherapy. Increasing evidences indicate that the antitumor activity of platinum complexes is not limited to chemical killing effects, but also extends to immunomodulatory actions. This review introduced the general concept of chemoimmunotherapy and summarized the progress of platinum complexes as chemoimmunotherapeutic agents in recent years. Platinum complexes could be developed into inducers of immunogenic cell death, blockers of immune checkpoint, regulators of immune signaling pathway, and modulators of tumor immune microenvironment, etc. The synergy between chemotherapeutic and immunomodulatory effects reinforces the antitumor activity of platinum complexes, and helps them circumvent the drug resistance and systemic toxicity. The exploration of platinum complexes for chemoimmunotherapy may create new opportunities to revive the discovery of metal anticancer drugs.

Silk fibroin/polyvinyl alcohol composite film loaded with antibacterial AgNP/polydopamine-modified montmorillonite; characterization and antibacterial properties.

In this study, a kind of nanocomposite film was fabricated via combining silk fibroin, polyvinyl alcohol (SF/PVA) and AgNP/polydopamine-modified Montmorillonite (AgNP/PDA-Mt). The structural characteristics and properties of the SF/PVA/AgNP/PDA-Mt nanocomposites films were identified using X-ray diffraction (XRD), Thermal gravimetric analyzer (TGA), Fourier transform infrared spectroscopy (FTIR), EDS-mapping analyses and Scanning electron microscope (SEM). The results indicated enhanced thermal performance of SF/PVA/AgNP/PDA-Mt nanocomposites with increased AgNP/PDA-Mt weight. The nanocomposite film exhibited excellent antibacterial activity against E. coli and S. aureus. The 2 % SF/PVA/AgNP/PDA-Mt film showed the highest zone of inhibition with an average inhibition circle diameter of 26.1 mm against E. coli and 20.61 mm against S. aureus. Cytotoxicity test results indicated that the nanocomposites films were biocompatible with L929 cells with a 100 % survival rate, which can be considered as one of the advantages of new nanocomposites films. These findings suggest that SF/PVA/AgNP/PDA-Mt films have potential clinical applications in wound dressing and antibacterial biomedical applications.

Regulating tumor glycometabolism and the immune microenvironment by inhibiting lactate dehydrogenase with platinum(iv) complexes.

Lactate dehydrogenase (LDH) is a key enzyme involved in the process of glycolysis, assisting cancer cells to take in glucose and generate lactate, as well as to suppress and evade the immune system by altering the tumor microenvironment (TME). Platinum(iv) complexes MDP and DDP were prepared by modifying cisplatin with diclofenac at the axial position(s). These complexes exhibited potent antiproliferative activity against a panel of human cancer cell lines. In particular, DDP downregulated the expression of LDHA, LDHB, and MCTs to inhibit the production and influx/efflux of lactate in cancer cells, impeding both glycolysis and glucose oxidation. MDP and DDP also reduced the expression of HIF-1α, ARG1 and VEGF, thereby disrupting the formation of tumor vasculature. Furthermore, they promoted the repolarization of macrophages from the tumor-supportive M2 phenotype to the tumor-suppressive M1 phenotype in the TME, thus enhancing the antitumor immune response. The antitumor mechanism involves reprogramming the energy metabolism of tumor cells and relieving the immunosuppressive TME.

Amlexanox-modified platinum(IV) complex triggers apoptotic and autophagic bimodal death of cancer cells.

Platinum(IV) prodrugs c,c,t-[PtCl2(NH3)2(OH)(amlexanox)] (MAP) and c,c,t-[PtCl2(NH3)2(amlexanox)2] (DAP) were synthesized by reacting amlexanox with oxoplatin and characterized by NMR, HR-MS, HPLC, and elemental analysis. The complexes could be reduced to platinum(II) species and amlexanox to exert antitumor activity. Generally, MAP was more potent than DAP and cisplatin towards various human cancer cell lines; particularly, it was active in cisplatin-resistant Caov-3 ovarian cancer and A549/DDP lung cancer cells. MAP induced serious damage to DNA, remarkable change in mitochondrial morphology, decrease in mitochondrial membrane potential, release of cytochrome c from mitochondria, and up-regulation of pro-apoptotic protein Bax in Caov-3 cells, thereby leading to evident apoptosis. Meanwhile, MAP markedly promoted the autophagic flux, including affecting the expression of microtubule-associated protein light chain 3 (LC3) and autophagy adaptor protein p62 in Caov-3 cells, with an increase in the ratio of LC3-II/LC3-I and a decrease in p62, thus trigging the occurrence of autophagy. The MAP-induced bimodal cell death mode is uncommon for platinum complexes, which presents a new possibility to invent anticancer drugs with unique mechanism of action.

Golgi apparatus-targeted aggregation-induced emission luminogens for effective cancer photodynamic therapy.

Golgi apparatus (GA) oxidative stress induced by in situ reactive oxygen species (ROS) could severely damage the morphology and function of GA, which may open up an avenue for effective photodynamic therapy (PDT). However, due to the lack of effective design strategy, photosensitizers (PSs) with specific GA targeting ability are in high demand and yet quite challenging. Herein, we report an aggregation-induced emission luminogen (AIEgen) based PS (TPE-PyT-CPS) that can effectively target the GA via caveolin/raft mediated endocytosis with a Pearson correlation coefficient up to 0.98. Additionally, the introduction of pyrene into TPE-PyT-CPS can reduce the energy gap between the lowest singlet state (S1) and the lowest triplet state (T1) (ΔEST) and exhibits enhanced singlet oxygen generation capability. GA fragmentation and cleavage of GA proteins (p115/GM130) are observed upon light irradiation. Meanwhile, the apoptotic pathway is activated through a crosstalk between GA oxidative stress and mitochondria in HeLa cells. More importantly, GA targeting TPE-T-CPS show better PDT effect than its non-GA-targeting counterpart TPE-PyT-PS, even though they possess very close ROS generation rate. This work provides a strategy for the development of PSs with specific GA targeting ability, which is of great importance for precise and effective PDT.

Concurrent suppression of Aß aggregation and NLRP3 inflammasome activation for treating Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative illness accompanied by severe memory loss, cognitive disorders and impaired behavioral ability. Amyloid ß-peptide (Aß) aggregation and nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome play crucial roles in the pathogenesis of AD. Aß plaques not only induce oxidative stress and impair neurons, but also activate the NLRP3 inflammasome, which releases inflammatory cytokine IL-1ß to trigger neuroinflammation. A bifunctional molecule, 2-[2-(benzo[d]thiazol-2-yl)phenylamino]benzoic acid (BPBA), with both Aß-targeting and inflammasome-inhibiting capabilities was designed and synthesized. BPBA inhibited self- and Cu2+- or Zn2+-induced Aß aggregation, disaggregated the already formed Aß aggregates, and reduced the neurotoxicity of Aß aggregates; it also inhibited the activation of the NLRP3 inflammasome and reduced the release of IL-1ß in vitro and vivo. Moreover, BPBA decreased the production of reactive oxygen species (ROS) and alleviated Aß-induced paralysis in transgenic C. elegans with the human Aß42 gene. BPBA exerts an anti-AD effect mainly through dissolving Aß aggregates and inhibiting NLRP3 inflammasome activation synergistically.

DNA-Unresponsive Platinum(II) Complex Induces ERS-Mediated Mitophagy in Cancer Cells.

Mitophagy is a selective autophagic process that degrades dysfunctional mitochondria. Monofunctional platinum(II) complexes are candidates for anticancer drugs with the potential to circumvent the drug resistance and side effects of cisplatin and its analogues, but their mechanism of action is elusive. Complex Mono-Pt kills cancer cells through a mitophagic pathway. The mechanism involves the stimulation of endoplasmic reticulum stress (ERS) and activation of the unfolded protein response. Mono-Pt severely impairs the structure and function of mitochondria, including disruption of morphological integrity, dissipation of membrane potential, elevation of reactive oxygen species, inhibition of mtDNA transcription, and reduction of adenosine triphosphate (ATP), which ultimately leads to mitophagy. Mono-Pt does not react with nuclear DNA but exhibits potent antiproliferative activity against cancer cells, thus breaking the DNA-binding paradigm and classical structure-activity rules for platinum drugs. The ERS-mediated mitophagy provides an alternative mechanism for platinum complexes, which broadens the way for developing new platinum anticancer drugs.

Platinum(IV) complexes as inhibitors of CD47-SIRPα axis for chemoimmunotherapy of cancer.

Phagocytosis of cancer cells by antigen presenting cells (APCs) is critical to activate the host's immune responses. However, the targeting ability of APCs to cancer cells is limited by the upregulation of transmembrane protein CD47 on the cancer cell surface. Blocking CD47 can affect the macrophage-mediated phagocytosis. Two platinum-based immunomodulators MUP and DMUP were synthesized to enhance the phagocytic activity of macrophages by blocking the CD47-SIRPα axis. These PtIV complexes not only showed high antiproliferative activity against a panel of human cancer cell lines, but also cooperated with human peripheral blood mononuclear cells (PBMCs) to suppress cancer cells. They acted as immune checkpoint inhibitors to modulate the immune responses of both cancer and immune cells. In particular, DMUP decreased the expression of CD47 in tumor tissues and promoted the polarization of macrophages from M2 to M1 phenotype in a mouse model of non-small cell lung cancer, thereby enhancing the anticancer effect. By interfering with DNA synthesis and stimulating immune system, DMUP takes the advantage of chemotherapy and immunotherapy to inhibit cancer cells. The dual efficacy of DMUP makes it a potential chemoimmunotherapeutic agent in cancer therapy.

Assessing Impact of Platinum Complexes on Mitochondrial Functions.

Platinum-based antitumor drugs play important roles in the clinical treatment of various tumors. Nevertheless, some deficiencies such as poor targeting ability, low bioavailability, in vivo deactivation, drug resistance, and side effects undermine the efficacy of these drugs. Mitochondria are important organelles which regulate the energy metabolism, physiological function, life span, and survival of the cells. Regulating or interfering with mitochondrial metabolism is of great significance in the prevention or treatment of cancers. Thus, a series of mitochondrion-targeted platinum complexes were prepared by modifying triphenylphosphine (TPP+) through chemical modifications, which endow traditional platinum drugs with new properties and mechanisms through interfering with mitochondrial DNA (mtDNA), mitochondrial membrane potential (MMP), mitochondrial morphology, mitochondrial bioenergetics, or production of reactive oxygen species (ROS), thereby opening a new path for the clinical application of platinum drugs. Here we introduce the synthesis of some TPP+-modified platinum (II, IV) complexes in details and the detection method of the activity parameters related to the mitochondrial functions.

Monofunctional Platinum(II) Anticancer Agents.

Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side effects. Much effort has been made to circumvent the drug resistance and general toxicity of these drugs. Among multifarious designs, monofunctional platinum(II) complexes with a general formula of [Pt(3A)Cl]+ (A: Ammonia or amine) stand out as a class of "non-traditional" anticancer agents hopeful to overcome the defects of current platinum drugs. This review aims to summarize the development of monofunctional platinum(II) complexes in recent years. They are classified into four categories: fluorescent complexes, photoactive complexes, targeted complexes, and miscellaneous complexes. The intention behind the designs is either to visualize the cellular distribution, or to reduce the side effects, or to improve the tumor selectivity, or inhibit the cancer cells through non-DNA targets. The information provided by this review may inspire researchers to conceive more innovative complexes with potent efficacy to shake off the drawbacks of platinum anticancer drugs.

Immunogenicity and cytotoxicity of a platinum(IV) complex derived from capsaicin.

Platinum-based anticancer drugs constitute the cornerstone of chemotherapy for various cancers. Although cytotoxic agents are considered to have immunosuppressive effects, increasing evidence suggests that some cytotoxic compounds can effectively stimulate the antitumor immune response by inducing a special type of apoptosis called immunogenic cell death (ICD). A platinum(iv) complex (DCP) modified with the derivative of synthetic capsaicin (nonivamide) was designed to elicit ICD. The complex exhibited high cytotoxicity against a panel of human cancer cell lines including pancreas (PANC-1), breast (MCF-7), and liver (HepG2) cancer cells, and osteosarcoma (MG-63) cells. In addition to causing DNA damage, DCP also triggered the translocation of calreticulin (CRT) as well as the release of ATP and HMGB1 protein in PANC-1 cells, thus manifesting an efficient ICD-inducing effect on cancer cells. Furthermore, the DCP-treated PANC-1 cell-conditioned culture medium promoted the release of IFN-γ and TNF-α to induce the immune response of human peripheral blood mononuclear cells, thereby increasing their cytotoxicity to cancer cells. Concurrently, the phagocytosis of PANC-1 cells by macrophages was also augmented by DCP. The results demonstrate that DCP is an effective inducer of ICD and a potential agent for chemoimmunotherapy of cancers.

Multispecific Platinum(IV) Complex Deters Breast Cancer via Interposing Inflammation and Immunosuppression as an Inhibitor of COX-2 and PD-L1.

Breast cancer (BC) is one of the most common malignancies in women and often accompanied by inflammatory processes. Cyclooxygenase-2 (COX-2) plays a vital role in the progression of BC, correlating with the expression of programmed death-ligand 1 (PD-L1). Overexpression of PD-L1 contributes to the immune escape of cancer cells, and its blockade would stimulate anticancer immunity. Two multispecific platinum(IV) complexes DNP and NP were prepared using non-steroidal antiinflammatory drug naproxen (NPX) as axial ligand(s) to inhibit the BC cells. DNP exhibited high cytotoxicity and antiinflammatory properties superior over NP, cisplatin and NPX; moreover, it displayed potent antitumor activity and almost no general toxicity in mice bearing triple-negative breast cancer (TNBC). Mechanistic studies revealed that DNP could downregulate the expression of COX-2 and PD-L1 in vitro and vivo, inhibit the secretion of prostaglandin, reduce the expression of BC-associated protein BRD4 and phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2), and block the oncogene c-Myc in BC cells. These findings demonstrate that DNP is capable of intervening in inflammatory, immune, and metastatic processes of BC, thus presenting a new mechanism of action for anticancer platinum(IV) complexes. The multispecificity offers a special superiority for DNP to treat TNBC by combining chemotherapy and immunotherapy in one molecule.

Targeting Energy Metabolism by a Platinum(IV) Prodrug as an Alternative Pathway for Cancer Suppression.

Cancer is characterized by abnormal cellular energy metabolism, which preferentially switches to aerobic glycolysis rather than oxidative phosphorylation as a means of glucose metabolism. Many key enzymes involved in the abnormal glycolysis are potential targets of anticancer drugs. Platinum(IV) complexes are potential anticancer prodrugs and kinetically more inert than the platinum(II) counterparts, which offer an opportunity to be modified by functional ligands for activation or targeted delivery. A novel platinum(IV) complex, c, c, t-[Pt(NH3)2Cl2(C10H15N2O3S)(C2HO2Cl2)] (DPB), was designed to explore the effects of axial ligands on the reactivity and bioactivity of the complex as well as on tumor energy metabolism. The complex was characterized by electrospray ionization mass spectrometry and multinuclear (1H, 13C, and 195Pt) NMR spectroscopy. The introduction of dichloroacetate (DCA) markedly increases the lipophilicity, reactivity, and cytotoxicity of the complex and blocks the growth of cancer cells having active glycolysis, and the introduction of biotin (C10H16N2O3S) enhances the tumor-targeting potential of the complex. The cytotoxicity of DPB is increased dramatically in a variety of cancer cell lines as compared with the platinum(IV) complex PB without the DCA group. DPB alters the mitochondrial membrane potential and disrupts the mitochondrial morphology. The levels of mitochondrial and cellular reactive oxygen species are also decreased. Furthermore, the mitochondrial function of tumor cells was impaired by DPB, leading to the inhibition of both glycolysis and glucose oxidation and finally to the death of cancer cells via a mitochondria-mediated apoptotic pathway. These findings demonstrate that DPB suppresses cancer cells mainly through altering metabolic pathways and highlight the importance of dual-targeting for the efficacy of anticancer drugs.

A platinum(iv) prodrug to defeat breast cancer through disrupting vasculature and inhibiting metastasis.

A PtIV prodrug (PDMA) exhibits great potential for the therapy of metastatic triple-negative breast cancer (TNBC) through a synergistic action of antiangiogensis and antimetastasis.

Alleviation of symptoms of Alzheimer's disease by diminishing Aß neurotoxicity and neuroinflammation.

Alzheimer's disease (AD) is one of the most prevailing neurodegenerative illnesses in the elderly. Accumulation of amyloid-ß peptide (Aß) and inflammation play critical roles in the pathogenesis and development of AD. Multi-target drugs may interdict the progress of AD through a synergistic mechanism. A neuromodulator, 2-((1H-benzo[d]imidazole-2-yl)methoxy)benzoic acid (BIBA), consisting of an Aß-targeting group and a derivative of anti-inflammatory aspirin was designed as a potential anti-AD agent. BIBA exhibits a remarkable inhibitory effect on the self- and metal-induced Aß aggregations and shows outstanding anti-inflammatory activity simultaneously. The neurotoxicity of Aß aggregates is attenuated, and the production of pro-inflammatory cytokines (PICs), such as IL-6, IL-1ß and TNF-α, in microglia stimulated by lipopolysaccharide (LPS) or Aß is reduced. Owing to the synergy between the inhibition of Aß oligomerization and downregulation of PICs, BIBA markedly prolongs the lifespan and relieves the Aß-induced paralysis of Aß-transgenic Caenorhabditis elegans, thus showing the potential to ameliorate the symptoms of AD through inhibiting Aß neurotoxicity and deactivating microglia. These findings demonstrate that both Aß aggregation and neuroinflammation are therapeutic targets for anti-AD drugs, and dual-functional agents that integrate anti-Aß and anti-inflammatory capabilities have great advantages over the traditional single-target agents for AD treatment.

Stimuli-Responsive Therapeutic Metallodrugs.

The success of platinum-based anticancer agents has motivated the exploration of novel metal-based drugs for several decades, whereas problems such as drug-resistance and systemic toxicity hampered their clinical applications and efficacy. Stimuli-responsiveness of some metal complexes offers a good opportunity for designing site-specific prodrugs to maximize the therapeutic efficacy and minimize the side effect of metallodrugs. This review presents a comprehensive and up-to-date overview on the therapeutic stimuli-responsive metallodrugs that have appeared in the past two decades, where stimuli such as redox, pH, enzyme, light, temperature, and so forth were involved. The compounds are classified into three major categories based on the nature of stimuli, that is, endo-stimuli-responsive metallodrugs, exo-stimuli-responsive metallodrugs, and dual-stimuli-responsive metallodrugs. Representative examples of each type are discussed in terms of structure, response mechanism, and potential medical applications. In the end, future opportunities and challenges in this field are tentatively proposed. With diverse metal complexes being introduced, the foci of this review are pointed to platinum and ruthenium complexes.

Impact of Mitochondrion-Targeting Group on the Reactivity and Cytostatic Pathway of Platinum(IV) Complexes.

Platinum(IV) complexes are prodrugs of cisplatin with multiple potential advantages over platinum(II) drugs. Mitochondria play pivotal roles in producing energy and inducing death of cancer cells. Two platinum(IV) complexes, namely, c,c,t-[Pt(NH3)2Cl2(OH)(OCOCH2CH2CH2CH2PPh3)]Br and c,c,t-[Pt(NH3)2Cl2(OCOCH2CH2CH2CH2PPh3)2]Br2, were designed to explore the effect of mitochondrion-targeting group(s) on the bioactivity and cytotoxicity of platinum(IV) complexes. The complexes were characterized by electrospray ionization mass spectrometry, reverse-phase high-performance liquid chromatography, and multinuclear (1H, 13C, 31P, and 195Pt) NMR spectroscopy. The introduction of triphenylphosphonium targeting group(s) markedly influences the reactivity and cytotoxicity of the Pt(IV) complexes. The targeted complex displays more potent disruptive effect on mitochondria but less inhibitory effect on cancer cells than cisplatin. The lipophilicity of the Pt(IV) complexes is enhanced by the targeting group(s), while their reactivity to DNA is decreased. As a result, the mitochondrial morphology and adenosine triphosphate producing ability are impaired, which constitutes an alternative pathway to inhibit cancer cells. This study shows that both the reactivity of platinum(IV) center and the property of axial targeting ligand exert influences on the cytotoxicity of targeted Pt(IV) complexes. For targeting groups with pharmacological activities, their intrinsic function could enrich the anticancer mechanism of Pt(IV) complexes.

Synthesis and anticoagulation activities of polymer/functional graphene oxide nanocomposites via Reverse Atom Transfer Radical Polymerization (RATRP).

The anticoagulation properties of biomaterials are crucial for biomedical applications, especially for blood-contacting materials. In this work, a range of functional graphene oxide based on the biomimetic monomer 2-(methacryloyloxy) ethyl phosphorylcholine (GO-g-pMPC) were synthesized by RATRP in alcoholic media using peroxide groups as initiator, and then filled into the polyurethane matrix to obtain the polyurethane (PU)/functional graphene oxide nanocomposite films (PU/GO-g-pMPC). The tensile strength and elongation and morphology of the PU/GO-g-pMPC were characterized by mechanical properties test, Transmission electron microscope (TEM), respectively. The results showed that a small amount of graphene oxide can improve the mechanical properties of PU. The blood compatibility of the PU substrates was evaluated by protein adsorption tests and platelet adhesion tests in vitro. It was found that all the PU/GO-g-pMPC showed improved resistance to nonspecific protein adsorption and platelet adhesion.