Photo/radiosensitizers, such as octahedral molybdenum clusters (Mo6), have been intensively studied for photodynamic applications to treat various diseases. However, their delivery to the desired target can be hampered by its limited solubility, low stability in physiological conditions, and inappropriate biodistribution, thus limiting the therapeutic effect and increasing the side effects of the therapy. To overcome such obstacles and to prepare photofunctional nanomaterials, we employed biocompatible and water-soluble copolymers based on N-(2-hydroxypropyl)methacrylamide (pHPMA) as carriers of Mo6 clusters. Several strategies based on electrostatic, hydrophobic, or covalent interactions were employed for the formation of polymer-cluster constructs. Importantly, the luminescent properties of the Mo6 clusters were preserved upon association with the polymers: all polymer-cluster constructs exhibited an effective quenching of their excited states, suggesting a production of singlet oxygen (O2(1Δg)) species which is a major factor for a successful photodynamic treatment. Even though the colloidal stability of all polymer-cluster constructs was satisfactory in deionized water, the complexes prepared by electrostatic and hydrophobic interactions underwent severe aggregation in phosphate buffer saline (PBS) accompanied by the disruption of the cohesive forces between the cluster and polymer molecules. On the contrary, the conjugates prepared by covalent interactions notably displayed colloidal stability in PBS in addition to high luminescence quantum yields, suggesting that pHPMA is a suitable nanocarrier for molybdenum cluster-based photosensitizers intended for photodynamic applications.

Institute of Inorganic Chemistry of the Czech Academy of Sciences 250 68 Husinec Řež 1001 Czech Republic

Institute of Macromolecular Chemistry of the Czech Academy of Sciences Heyrovského Náměstí 2 162 06 Prague 6 Czech Republic

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Maeda H., Nakamura H., Fang J. The EPR effect for macromolecular drug delivery to solid tumors: Improvement of tumor uptake, lowering of systemic toxicity, and distinct tumor imaging in vivo. Adv. Drug Deliv. Rev. 2013;65:71–79. doi: 10.1016/j.addr.2012.10.002. PubMed DOI

Fang J., Šubr V., Islam W., Hackbarth S., Islam R., Etrych T., Ulbrich K., Maeda H. N-(2-hydroxypropyl)methacrylamide polymer conjugated pyropheophorbide-a, a promising tumor-targeted theranostic probe for photodynamic therapy and imaging. Eur. J. Pharm. Biopharm. 2018;130:165–176. doi: 10.1016/j.ejpb.2018.06.005. PubMed DOI

Berg K., Selbo P.K., Weyergang A., Dietze A., Prasmickaite L., Bonsted A., Engesaeter B.Ø., Angell-Petersen E., Warloe T., Frandsen N., et al. Porphyrin-related photosensitizers for cancer imaging and therapeutic applications. Pt 2J. Microsc. 2005;218:133–147. doi: 10.1111/j.1365-2818.2005.01471.x. PubMed DOI

Li L., Huh K.M. Polymeric nanocarrier systems for photodynamic therapy. Biomater. Res. 2014;18:19. doi: 10.1186/2055-7124-18-19. PubMed DOI PMC

Chepurna O.M., Yakovliev A., Ziniuk R., Nikolaeva O.A., Levchenko S.M., Xu H., Losytskyy M.Y., Bricks J.L., Slominskii Y.L., Vretik L.O., et al. Core–shell polymeric nanoparticles co-loaded with photosensitizer and organic dye for photodynamic therapy guided by fluorescence imaging in near and short-wave infrared spectral regions. J. Nanobiotechnol. 2020;18:19. doi: 10.1186/s12951-020-0572-1. PubMed DOI PMC

Gibot L., Lemelle A., Till U., Moukarzel B., Mingotaud A.-F., Pimienta V., Saint-Aguet P., Rols M.-P., Gaucher M., Violleau F., et al. Polymeric Micelles Encapsulating Photosensitizer: Structure/Photodynamic Therapy Efficiency Relation. Biomacromolecules. 2014;15:1443–1455. doi: 10.1021/bm5000407. PubMed DOI

Lee Y.-E.K., Kopelman R. Methods in Molecular Biology. Volume 726. Springer; Clifton, NJ, USA: 2011. Polymeric Nanoparticles for Photodynamic Therapy; pp. 151–178. PubMed

Ricci-Júnior E., Marchetti J.M. Preparation, characterization, photocytotoxicity assay of PLGA nanoparticles containing zinc (II) phthalocyanine for photodynamic therapy use. J. Microencapsul. 2006;23:523–538. doi: 10.1080/02652040600775525. PubMed DOI

Weiss G.J., Chao J., Neidhart J.D., Ramanathan R.K., Bassett D., Neidhart J.A., Choi C.H.J., Chow W., Chung V., Forman S.J., et al. First-in-human phase 1/2a trial of CRLX101, a cyclodextrin-containing polymer-camptothecin nanopharmaceutical in patients with advanced solid tumor malignancies. Investig. New Drugs. 2013;31:986–1000. doi: 10.1007/s10637-012-9921-8. PubMed DOI PMC

Brandhonneur N., Hatahet T., Amela-Cortes M., Molard Y., Cordier S., Dollo G. Molybdenum cluster loaded PLGA nanoparticles: An innovative theranostic approach for the treatment of ovarian cancer. Eur. J. Pharm. Biopharm. 2018;125:95–105. doi: 10.1016/j.ejpb.2018.01.007. PubMed DOI

Kirakci K., Demel J., Hynek J., Zelenka J., Rumlová M., Ruml T., Lang K. Phosphinate Apical Ligands: A Route to a Water-Stable Octahedral Molybdenum Cluster Complex. Inorg. Chem. 2019;58:16546–16552. doi: 10.1021/acs.inorgchem.9b02569. PubMed DOI

Kirakci K., Zelenka J., Rumlová M., Cvačka J., Ruml T., Lang K. Cationic octahedral molybdenum cluster complexes functionalized with mitochondria-targeting ligands: Photodynamic anticancer and antibacterial activities. Biomater. Sci. 2019;7:1386–1392. doi: 10.1039/C8BM01564C. PubMed DOI

Brandhonneur N., Boucaud Y., Verger A., Dumait N., Molard Y., Cordier S., Dollo G. Molybdenum cluster loaded PLGA nanoparticles as efficient tools against epithelial ovarian cancer. Int. J. Pharm. 2021;592:120079. doi: 10.1016/j.ijpharm.2020.120079. PubMed DOI

Smith C.B., Days L.C., Alajroush D.R., Faye K., Khodour Y., Beebe S.J., Holder A.A. Photodynamic Therapy of Inorganic Complexes for the Treatment of Cancer†. Photochem. Photobiol. 2022;98:17–41. doi: 10.1111/php.13467. PubMed DOI

Kirakci K., Kubát P., Fejfarová K., Martinčík J., Nikl M., Lang K. X-ray Inducible Luminescence and Singlet Oxygen Sensitization by an Octahedral Molybdenum Cluster Compound: A New Class of Nanoscintillators. Inorg. Chem. 2016;55:803–809. doi: 10.1021/acs.inorgchem.5b02282. PubMed DOI

Kirakci K., Zelenka J., Rumlová M., Martinčík J., Nikl M., Ruml T., Lang K. Octahedral molybdenum clusters as radiosensitizers for X-ray induced photodynamic therapy. J. Mater. Chem. B. 2018;6:4301–4307. doi: 10.1039/C8TB00893K. PubMed DOI

Kirakci K., Pozmogova T.N., Protasevich A.Y., Vavilov G.D., Stass D.V., Shestopalov M.A., Lang K. A water-soluble octahedral molybdenum cluster complex as a potential agent for X-ray induced photodynamic therapy. Biomater. Sci. 2021;9:2893–2902. doi: 10.1039/D0BM02005B. PubMed DOI

Koncošová M., Rumlová M., Mikyšková R., Reiniš M., Zelenka J., Ruml T., Kirakci K., Lang K. Avenue to X-ray-induced photodynamic therapy of prostatic carcinoma with octahedral molybdenum cluster nanoparticles. J. Mater. Chem. B. 2022;10:3303–3310. doi: 10.1039/D2TB00141A. PubMed DOI

Felip-León C., Arnau del Valle C., Pérez-Laguna V., Isabel Millán-Lou M., Miravet J.F., Mikhailov M., Sokolov M.N., Rezusta-López A., Galindo F. Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials. J. Mater. Chem. B. 2017;5:6058–6064. doi: 10.1039/C7TB01478C. PubMed DOI

Vorotnikova N.A., Alekseev A.Y., Vorotnikov Y.A., Evtushok D.V., Molard Y., Amela-Cortes M., Cordier S., Smolentsev A.I., Burton C.G., Kozhin P.M., et al. Octahedral molybdenum cluster as a photoactive antimicrobial additive to a fluoroplastic. Mater. Sci. Eng. C. 2019;105:110150. doi: 10.1016/j.msec.2019.110150. PubMed DOI

Kirakci K., Nguyen T.K.N., Grasset F., Uchikoshi T., Zelenka J., Kubát P., Ruml T., Lang K. Electrophoretically Deposited Layers of Octahedral Molybdenum Cluster Complexes: A Promising Coating for Mitigation of Pathogenic Bacterial Biofilms under Blue Light. ACS Appl. Mater. Interfaces. 2020;12:52492–52499. doi: 10.1021/acsami.0c19036. PubMed DOI

López-López N., Muñoz Resta I., de Llanos R., Miravet J.F., Mikhaylov M., Sokolov M.N., Ballesta S., García-Luque I., Galindo F. Photodynamic Inactivation of Staphylococcus aureus Biofilms Using a Hexanuclear Molybdenum Complex Embedded in Transparent polyHEMA Hydrogels. ACS Biomater. Sci. Eng. 2020;6:6995–7003. doi: 10.1021/acsbiomaterials.0c00992. PubMed DOI

Jackson J.A., Turro C., Newsham M.D., Nocera D.G. Oxygen quenching of electronically excited hexanuclear molybdenum and tungsten halide clusters. J. Phys. Chem. 1990;94:4500–4507. doi: 10.1021/j100374a029. DOI

Kirakci K., Kubát P., Langmaier J., Polívka T., Fuciman M., Fejfarová K., Lang K. A comparative study of the redox and excited state properties of (nBu4N)2[Mo6X14] and (nBu4N)2[Mo6X8(CF3COO)6] (X = Cl, Br, or I) Dalt. Trans. 2013;42:7224. doi: 10.1039/c3dt32863e. PubMed DOI

Kirakci K., Kubáňová M., Přibyl T., Rumlová M., Zelenka J., Ruml T., Lang K. A Cell Membrane Targeting Molybdenum-Iodine Nanocluster: Rational Ligand Design toward Enhanced Photodynamic Activity. Inorg. Chem. 2022;61:5076–5083. doi: 10.1021/acs.inorgchem.2c00040. PubMed DOI

Aubert T., Burel A., Esnault M.A., Cordier S., Grasset F., Cabello-Hurtado F. Root uptake and phytotoxicity of nanosized molybdenum octahedral clusters. J. Hazard. Mater. 2012;219–220:111–118. doi: 10.1016/j.jhazmat.2012.03.058. PubMed DOI

Nakamura H., Liao L., Hitaka Y., Tsukigawa K., Subr V., Fang J., Ulbrich K., Maeda H. Micelles of zinc protoporphyrin conjugated to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer for imaging and light-induced antitumor effects in vivo. J. Control. Release. 2013;165:191–198. doi: 10.1016/j.jconrel.2012.11.017. PubMed DOI

Ulbrich K., Šubr V., Strohalm J., Plocová D., Jelínková M., Říhová B. Polymeric drugs based on conjugates of synthetic and natural macromolecules. I. Synthesis and physico-chemical characterisation. J. Control. Release. 2000;64:63–79. doi: 10.1016/S0168-3659(99)00141-8. PubMed DOI

Šubr V., Ulbrich K. Synthesis and properties of new N-(2-hydroxypropyl)-methacrylamide copolymers containing thiazolidine-2-thione reactive groups. React. Funct. Polym. 2006;66:1525–1538. doi: 10.1016/j.reactfunctpolym.2006.05.002. DOI

Chytil P., Etrych T., Koňák Č., Šírová M., Mrkvan T., Bouček J., Říhová B., Ulbrich K. New HPMA copolymer-based drug carriers with covalently bound hydrophobic substituents for solid tumour targeting. J. Control. Release. 2008;127:121–130. doi: 10.1016/j.jconrel.2008.01.007. PubMed DOI

Bojarová P., Tavares M.R., Laaf D., Bumba L., Petrásková L., Konefał R., Bláhová M., Pelantová H., Elling L., Etrych T., et al. Biocompatible glyconanomaterials based on HPMA-copolymer for specific targeting of galectin-3. J. Nanobiotechnol. 2018;16:73. doi: 10.1186/s12951-018-0399-1. PubMed DOI PMC

Chytil P., Etrych T., Kříž J., Subr V., Ulbrich K. N-(2-Hydroxypropyl)methacrylamide-based polymer conjugates with pH-controlled activation of doxorubicin for cell-specific or passive tumour targeting. Synthesis by RAFT polymerisation and physicochemical characterisation. Eur. J. Pharm. Sci. 2010;41:473–482. doi: 10.1016/j.ejps.2010.08.003. PubMed DOI

Perrier S., Takolpuckdee P., Mars C.A. Reversible Addition−Fragmentation Chain Transfer Polymerization: End Group Modification for Functionalized Polymers and Chain Transfer Agent Recovery. Macromolecules. 2005;38:2033–2036. doi: 10.1021/ma047611m. DOI

Machová D., Koziolová E., Chytil P., Venclíková K., Etrych T., Janoušková O. Nanotherapeutics with suitable properties for advanced anticancer therapy based on HPMA copolymer-bound ritonavir via pH-sensitive spacers. Eur. J. Pharm. Biopharm. 2018;131:141–150. doi: 10.1016/j.ejpb.2018.07.023. PubMed DOI

Kirakci K., Zelenka J., Křížová I., Ruml T., Lang K. Octahedral Molybdenum Cluster Complexes with Optimized Properties for Photodynamic Applications. Inorg. Chem. 2020;59:9287–9293. doi: 10.1021/acs.inorgchem.0c01173. PubMed DOI

Kirakci K., Kubát P., Kučeráková M., Šícha V., Gbelcová H., Lovecká P., Grznárová P., Ruml T., Lang K. Water-soluble octahedral molybdenum cluster compounds Na2[Mo6I8(N3)6] and Na2[Mo6I8(NCS)6]: Syntheses, luminescence, and in vitro studies. Inorganica Chim. Acta. 2016;441:42–49. doi: 10.1016/j.ica.2015.10.043. DOI

Etrych T., Mrkvan T., Chytil P., Koňák Č., Říhová B., Ulbrich K. N-(2-hydroxypropyl)methacrylamide-based polymer conjugates with pH-controlled activation of doxorubicin. I. New synthesis, physicochemical characterization and preliminary biological evaluation. J. Appl. Polym. Sci. 2008;109:3050–3061. doi: 10.1002/app.28466. DOI

Fang J., Islam W., Maeda H. Exploiting the dynamics of the EPR effect and strategies to improve the therapeutic effects of nanomedicines by using EPR effect enhancers. Adv. Drug Deliv. Rev. 2020;157:142–160. doi: 10.1016/j.addr.2020.06.005. PubMed DOI

Pola R., Braunová A., Laga R., Pechar M., Ulbrich K. Click chemistry as a powerful and chemoselective tool for the attachment of targeting ligands to polymer drug carriers. Polym. Chem. 2014;5:1340–1350. doi: 10.1039/C3PY01376F. DOI

Filippov S.K., Chytil P., Konarev P.V., Dyakonova M., Papadakis C., Zhigunov A., Plestil J., Stepanek P., Etrych T., Ulbrich K., et al. Macromolecular HPMA-based nanoparticles with cholesterol for solid-tumor targeting: Detailed study of the inner structure of a highly efficient drug delivery system. Biomacromolecules. 2012;13:2594–2604. doi: 10.1021/bm3008555. PubMed DOI

Chytil P., Etrych T., Kostka L., Ulbrich K. Hydrolytically Degradable Polymer Micelles for Anticancer Drug Delivery to Solid Tumors. Macromol. Chem. Phys. 2012;213:858–867. doi: 10.1002/macp.201100632. DOI

Filippov S.K., Vishnevetskaya N.S., Niebuur B.J., Koziolová E., Lomkova E.A., Chytil P., Etrych T., Papadakis C.M. Influence of molar mass, dispersity, and type and location of hydrophobic side chain moieties on the critical micellar concentration and stability of amphiphilic HPMA-based polymer drug carriers. Colloid Polym. Sci. 2017;295:1313–1325. doi: 10.1007/s00396-017-4027-7. DOI

Chytil P., Šírová M., Kudláčová J., Říhová B., Ulbrich K., Etrych T. Bloodstream Stability Predetermines the Antitumor Efficacy of Micellar Polymer–Doxorubicin Drug Conjugates with pH-Triggered Drug Release. Mol. Pharm. 2018;15:3654–3663. doi: 10.1021/acs.molpharmaceut.8b00156. PubMed DOI

Braunová A., Chytil P., Laga R., Šírová M., Machová D., Parnica J., Říhová B., Janoušková O., Etrych T. Polymer nanomedicines based on micelle-forming amphiphilic or water-soluble polymer-doxorubicin conjugates: Comparative study of in vitro and in vivo properties related to the polymer carrier structure, composition, and hydrodynamic properties. J. Control. Release. 2020;321:718–733. doi: 10.1016/j.jconrel.2020.03.002. PubMed DOI

Lieber E., Rao C.N.R., Hoffman C.W.W., Chao T.S. Infrared Spectra of Organic Azides. Anal. Chem. 1957;29:916–918. doi: 10.1021/ac60126a016. DOI

Agrell I., Klæboe P., Pettersson B., Svensson S., Koskikallio J., Kachi S. The Infra-red Spectra of Some Inorganic Azide Compounds. Acta Chem. Scand. 1971;25:2965–2974. doi: 10.3891/acta.chem.scand.25-2965. DOI

Diana E., Gatterer K., Kettle S.F.A. The vibrational spectroscopy of the coordinated azide anion; A theoretical study. Phys. Chem. Chem. Phys. 2016;18:414–425. doi: 10.1039/C5CP05566K. PubMed DOI

Gai X.S., Coutifaris B.A., Brewer S.H., Fenlon E.E. A direct comparison of azide and nitrile vibrational probes. Phys. Chem. Chem. Phys. 2011;13:5926–5930. doi: 10.1039/c0cp02774j. PubMed DOI PMC