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Publication Open Access Broad spectrum antibacterial photodynamic and photothermal therapy achieved with indocyanine green loaded SPIONs under near infrared irradiation(Royal Society of Chemistry (RSC), 2020) N/A; Department of Physics; Department of Chemistry; Bilici, Kübra; Ataç, Nazlı; Muti, Abdullah; Toker, Işınsu Baylam; Doğan, Özlem; Sennaroğlu, Alphan; Can, Füsun; Acar, Havva Funda Yağcı; Researcher; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Physics; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; College of Sciences; N/A; N/A; N/A; N/A; 170418; 23851; 103165; 178902Antimicrobial photodynamic therapy (aPDT) and antimicrobial photothermal therapy (aPTT) are promising local and effective alternative therapies for antibiotic resistant bacterial infections and biofilms. A combination of nanoparticles and organic photosensitizers offers a great opportunity to combine PDT and PTT for effective eradication of both planktonic bacteria and their biofilms. In this work, photo-induced antibacterial activity of indocyanine green (ICG), 3-aminopropylsilane coated superparamagnetic iron oxide nanoparticles (APTMS@SPIONs) and ICG loaded APTMS@SPIONs was evaluated on planktonic cells and biofilms of Gram-negative (E. coli,K. pneumoniae,P. aeruginosa) and Gram-positive (S. epidermis) bacteria. A relatively low dose of ICG (25 mu g mL(-1)) and SPIONs (0.425 mu g mL(-1)nanoparticle) in combination with single, short (10 min) laser irradiation at 808 nm with a power of 1150 mW was used in this study. No dark toxicity of the agents or antibacterial effect of the laser irradiation was observed. The charge of the particles did not provide a significant difference in their penetration to Gram-negativeversusGram-positive bacterial strains or their biofilms. APTMS@SPION/laser treatment completely eliminatedP. aeruginosaand provided 7-log reduction in the colony forming unit (CFU) ofE. Coli, but was not effective on the other two bacteria. This is the first example for antibacterial phototoxicity of this nanoparticle. ICG/laser and ICG-APTMS@SPION/laser treatments provided complete killing of all planktonic cells. Successful eradication of all biofilms was achieved with ICG/laser (3.2-3.7 log reduction in CFUs) or ICG-APTMS@SPION/laser treatment (3.3-4.4 log reduction in CFUs). However, an exceptionally high, 6.5-log reduction as well as a dramatic difference between ICGversusICG/APTMS@SPION treatment was observed inK. pneumoniaebiofilms with ICG-APTMS@SPION/laser treatment. Investigation of the ROS production and increase in the local temperature of the biofilms that were subjected to phototherapy suggested a combination of aPTT and aPDT mechanisms for phototoxicity, exhibiting a synergistic effect when ICG-APTMS@SPION/laser was used. This approach opens an exciting and novel avenue in the fight against drug resistant infections by successfully utilizing the antimicrobial and antibiofilm activity of low dose FDA approved optically traceable ICG and relatively low cost clinically acceptable iron oxide nanoparticles to enable effective aPDT/aPTT combination, inducedviashort-duration laser irradiation at a near-infrared wavelength.Publication Open Access CdTe quantum dot sensitized hexaniobate nanoscrolls and their photoelectrochemical properties(Royal Society of Chemistry (RSC), 2012) Department of Chemistry; Öztuna, Feriha Eylül Saraç; Akkaya, Ceren Yılmaz; Acar, Havva Funda Yağcı; Ünal, Uğur; PhD Student; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; N/A; N/A; 178902; N/AWe have constructed hybrid quantum dot-layered niobate films with an electrophoretic deposition method. The structure and photoelectrochemical behaviour were demonstrated.Publication Open Access Cetuximab-Ag2S quantum dots for fluorescence imaging and highly effective combination of ALA-based photodynamic/chemo-therapy of colorectal cancer cells(Royal Society of Chemistry (RSC), 2021) Mohammad Hadi, Layla; Yaghini, Elnaz; Loizidou, Marilena; MacRobert, Alexander J.; Department of Chemistry; N/A; Department of Physics; Acar, Havva Funda Yağcı; Bayır, Ali; Hashemkhani, Mahshid; Demirci, Gözde; Muti, Abdullah; Sennaroğlu, Alphan; Researcher; PhD Student; Master Student; PhD Student; Faculty Member; Department of Chemistry; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering; 178902; N/A; N/A; N/A; N/A; 23851Colorectal cancer (CRC) has a poor prognosis and urgently needs better therapeutic approaches. 5-Aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) based photodynamic therapy (PDT) is already used in the clinic for several cancers but not yet well investigated for CRC. Currently, systemic administration of ALA offers a limited degree of tumour selectivity, except for intracranial tumours, limiting its wider use in the clinic. The combination of effective ALA-PDT and chemotherapy may provide a promising alternative approach for CRC treatment. Herein, theranostic Ag2S quantum dots (AS-2MPA) optically trackable in near-infrared (NIR), conjugated with endothelial growth factor receptor (EGFR) targeting Cetuximab (Cet) and loaded with ALA for PDT monotherapy or ALA/5-fluorouracil (5FU) for the combination therapy are proposed for enhanced treatment of EGFR(+) CRC. AS-2MPA-Cet exhibited excellent targeting of the high EGFR expressing cells and showed a strong intracellular signal for NIR optical detection in a comparative study performed on SW480, HCT116, and HT29 cells, which exhibit high, medium and low EGFR expression, respectively. Targeting provided enhanced uptake of the ALA loaded nanoparticles by strong EGFR expressing cells and formation of higher levels of PpIX. Cells also differ in their efficiency to convert ALA to PpIX, and SW480 was the best, followed by HT29, while HCT116 was determined as unsuitable for ALA-PDT. The therapeutic efficacy was evaluated in 2D cell cultures and 3D spheroids of SW480 and HT29 cells using AS-2MPA with either electrostatically loaded, hydrazone or amide linked ALA to achieve different levels of pH or enzyme sensitive release. Most effective phototoxicity was observed in SW480 cells using AS-2MPA-ALA-electrostatic-Cet due to enhanced uptake of the particles, fast ALA release and effective ALA-to-PpIX conversion. Targeted delivery reduced the effective ALA concentration significantly which was further reduced with codelivery of 5FU. Delivery of ALA via covalent linkages was also effective for PDT, but required a longer incubation time for the release of ALA in therapeutic doses. Phototoxicity was correlated with high levels of reactive oxygen species (ROS) and apoptotic/necrotic cell death. Hence, both AS-2MPA-ALA-Cet based PDT and AS-2MPA-ALA-Cet-5FU based chemo/PDT combination therapy coupled with strong NIR tracking of the nanoparticles demonstrate an exceptional therapeutic effect on CRC cells and excellent potential for synergistic multistage tumour targeting therapy.Publication Open Access Development of highly luminescent and cytocompatible near-IR-emitting aqueous Ag2S quantum dots(Royal Society of Chemistry (RSC), 2012) Çizmeciyan, M. Natali; Erdem, Rengin; Özen, Can; Kurt, Adnan; N/A; Department of Physics; Department of Chemistry; Hocaoğlu, İbrahim; Sennaroğlu, Alphan; Acar, Havva Funda Yağcı; PhD Student; Faculty Member; Department of Physics; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 23851; 178902Colloidally stable and highly luminescent near-IR emitting Ag2S quantum dots (NIRQDs) were prepared by a very simple aqueous method using 2-mercaptopropionic acid (2MPA) as a coating. Emission of Ag2S-2MPA NIRQDs can be tuned between 780 and 950 nm. These NIRQDs have photoluminescence quantum yields (PLQY) around 7–39% and exhibit excellent cytocompatibility even at 600 mg mL 1 in NIH/3T3 cells. With such improved properties, Ag2S-2MPA NIRQDs have a great potential in practical bio-applications.Publication Open Access Emission tunable, cyto/hemocompatible, near-IR-emitting Ag2S quantum dots by aqueous decomposition of DMSA(Royal Society of Chemistry (RSC), 2014) Sevrin, Chantal; Department of Chemistry; Department of Physics; Birer, Özgür; Hocaoğlu, İbrahim; Kiraz, Alper; Acar, Havva Funda Yağcı; Duman, Fatma Demir; Researcher; PhD Student; Faculty Member; Department of Chemistry; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; N/A; 22542; N/A; 178902Size tunable aqueous Ag2S quantum dots emitting in the near-infrared region were synthesized through decomposition of meso-2,3-dimercaptosuccinic acid (DMSA) in water. The resulting NIR QDs are highly cyto- and hemocompatible, have quantum yields as high as 6.5% and are effective optical imaging agents based on in vitro evaluation.Publication Open Access Heat transfer enhancement with actuation of magnetic nanoparticles suspended in a base fluid(American Institute of Physics (AIP) Publishing, 2012) Şeşen, Muhsincan; Tekşen, Yiğit; Mengüç, M. Pınar; Koşar, Ali; N/A; Department of Chemistry; Öztürk, Hande; Acar, Havva Funda Yağcı; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 178902In this study, we have experimentally demonstrated that heat transfer can be substantially increased by actuating magnetic nanoparticles inside a nanofluid. In order to materialize this, we have utilized a miniature heat transfer enhancement system based on the actuation of magnetic nanoparticles dispersed in a base fluid (water). This compact system consists of a pool filled with a nanofluid containing ferromagnetic nanoparticles, a heater, and two magnetic stirrers. The ferromagnetic particles within the pool were actuated with the magnetic stirrers. Single-phase heat transfer characteristics of the system were investigated at various fixed heat fluxes and were compared to those of stationary nanofluid (without magnetic stirring). The heat transfer enhancement realized by the circulation of ferromagnetic nanoparticles dispersed in a nanofluid was studied using the experimental setup. The temperatures were recorded from the readings of thin thermocouples, which were integrated to the heater surface. The surface temperatures were monitored against the input heat flux and data were processed to compare the heat transfer results of the configuration with magnetic stirrers to the heat transfer of the configuration without the magnetic stirrers. (C) 2012 American Institute of PhysicsPublication Open Access Highly luminescent and cytocompatible cationic Ag2S NIR-emitting quantum dots for optical imaging and gene transfection(Royal Society of Chemistry (RSC), 2015) Ozturk, Deniz Gulfem; Gozuacik, Devrim; Department of Chemistry; Department of Physics; Duman, Fatma Demir; Hocaoğlu, İbrahim; Kiraz, Alper; Acar, Havva Funda Yağcı; PhD Student; PhD Student; Faculty Member; Department of Chemistry; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 22542; 178902The development of non-toxic theranostic nanoparticles capable of delivering a therapeutic cargo and providing a means for diagnosis is one of the most challenging tasks in nano-biotechnology. Gene therapy is a very important mode of therapy and polyethyleneimine (PEI) is one of the most successful vehicles for gene transfection, yet poses significant toxicity. Optical imaging utilizing quantum dots is one of the newer but fast growing diagnostic modalities, which requires non-toxic, highly luminescent materials, preferentially active in the near infrared region. Ag2S NIRQDs fit to this profile perfectly. Here, we demonstrate the aqueous synthesis of cationic Ag2S NIRQDs with a mixed coating of 2-mercaptopropionic acid (2MPA) and PEI (branched, 25 kDa), which are highly luminescent in the NIR-I window (lambda(em) = 810-840 nm) as new theranostic nanoparticles. Synergistic stabilization of the QD surface via the simultaneous use of a small molecule and a polymeric material provided the highest quantum yield, 150% (with respect to LDS 798 at pH 7.4), reported in the literature for Ag2S. These cationic particles show a dramatic improvement in cytocompatibility even without PEGylation, a strong optical signal easily detected by confocal laser microscopy and effective conjugation and transfection of the green fluorescence protein plasmid (pGFP) to HeLa and MCF-7 cell lines (40% efficiency). Overall, these Ag2S NIRQDs show great potential as new theranostics.Publication Open Access Impact of reaction variables and PEI/L-cysteine ratio on the optical properties and cytocompatibility of cationic Ag2S quantum dots as NIR bio-imaging probes(Royal Society of Chemistry (RSC), 2016) Department of Chemistry; Duman, Fatma Demir; Khodadust, Rouhollah; Durmuşoğlu, Emek Göksu; Yağcı, Mustafa Barış; Acar, Havva Funda Yağcı; PhD Student; Other; Researcher; Department of Chemistry; College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A; 178902Near-infrared emitting semiconductor quantum dots (NIRQDs) are popular fluorescent probes due to better penetration depth and elimination of tissue autofluorescence. Here, we demonstrate one pot aqueous synthesis of cytocompatible, strongly luminescent, cationic Ag2S NIRQDs utilizing a mixed coating composed of branched polyethyleneimine (PEI)-25 kDa and L-cysteine (Cys) as in vitro luminescent tags and in vivo optical imaging agents. Ultrasmall sizes, a clear first excitonic peak in the absorption spectra, relatively narrow emission peaks with maxima between 730 and 775 nm and a Stokes shift less than 100 nm were obtained. Lifetime measurements indicate excitonic and defect-related emissions. Interestingly, not the emission maxima but the intensity was influenced by the Cys amount more dramatically. PEI/Cys 60/40 mol ratio provided the highest quantum yield reported until now for Ag2S NIRQD (157%) emitting at such a short wavelength. Low molecular weight PEI failed to produce luminescent QDs. Cytotoxicity evaluation of the most strongly luminescing NIRQDs, revealed the PEI/Cys (mol mol(-1)) 50/50 composition as the non-toxic composition below 2.4 mu g Ag per mL concentration. Others had low-toxicity. In vitro microscopy experiments showed endosomal distribution of NIRQDs in Hela cells and strong NIR signal. In vivo imaging study demonstrated that Ag2S NIRQDs could effectively be used as strong optical imaging agents.Publication Open Access In-situ synthesis of graphene encapsulated Fe/Fe2O3 nanoparticles for possible biomedical applications(Elsevier, 2022) Mertdinç Ülküseven, Sıddıka; Savacı, Umut; Öveçoğlu, M. Lütfi; Ağaoğulları, Duygu; Department of Chemistry; Acar, Havva Funda Yağcı; Balcı, Özge; Onbaşlı, Kübra; Researcher; Department of Chemistry; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); College of Sciences; 178902; 295531; N/AThis paper reports on the in-situ synthesis, optimization, characterization and cytotoxicity tests of multi-layer graphene (MLG) encapsulated Fe/Fe2O3 nanoparticles (Fe/Fe2O3@C core-shell nanostructures) by spray drying-assisted chemical vapor deposition (CVD) using iron-nitrate/silica-based precursors. The influences of CVD reaction temperature, holding time, CH4/H2 gas flows and pressure on the synthesis of MLG encapsulated Fe/Fe2O3 nanoparticles were investigated. CVD-synthesized powders were purified using acid leaching to remove residual silica and probable uncoated Fe/Fe-oxide phases. XRD analyses revealed the presence of FCC (Fe,C), BCC Fe, graphite/graphene and trace amount of Fe2O3 phases. Raman spectra confirmed the existence of MLG shells. TEM indicated that MLG (from at least 3 to maximum of 35 layers) wrapped around the metallic cores ranged be-tween 4 and 85 nm. Purification of nanoparticles did not degrade, dissolve or create discontinuity on the MLG structure. VSM measurements showed that nanoparticles obtained from the optimized conditions (900 ?, 100 ml/min CH4/H2, 50 mbar) had a soft ferromagnetic behavior with low saturation magnetization (-85 emu/g) and coercivity (-552 Oe) values. Optimized MLG encapsulated Fe/Fe2O3 nanoparticles were successfully suspended in water using a poly(acrylic acid) coating. Aqueous MLG encapsulated Fe/Fe2O3 nanoparticles were cytocompatible below 100 mg/ml at short incubation times, and showed the potential to be used in biomedical applications. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/).Publication Open Access Luminescent PbS and PbS/CdS quantum dots with hybrid coatings as nanotags for authentication of petroleum products(American Chemical Society (ACS), 2019) Durmuşoğlu, Emek Göksu; Türker, Yurdanur; Acar, Havva Funda Yağcı; Faculty Member; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; 178902There is an urgent need to tag some valuable liquid products, such as petroleum products, for authentication. However, it is a challenging task because of the strong autofluorescence of liquid petroleum products in the visible range and the chemically active and harsh medium. Therefore, strongly luminescent, near-infrared (NIR) fluorophores with long-term stability are needed. The use of NIR quantum dots (QDs), such as lead chalcogenides, seems to be the best approach; however, most widely used coatings do not provide enough stability, and QDs are quenched in a short time in liquid petroleum products. Here, we report for the first time the synthesis of highly luminescent, ultrasmall, NIR-emitting PbS and PbS/CdS QDs with a hybrid coating consisting of oleylamine (OLA), 1-dodecanethiol (DT), and poly(methacrylic acid) (PMAA), adopting a simple, greener synthetic method. The photoluminescence (PL) emission wavelengths of these QDs were tuned between 700 and 1100 nm for detection with low-cost, widely used silicon detectors, which allows easy translation of such QDs as luminescent nanotags to serve as a means for the authentication of goods, such as petroleum. In the nanoparticle design, a thin layer of a CdS shell deposited by a cation-exchange process was adopted to enhance the emission intensity and stability of PbS QDs. The influence of postsynthetic ligand exchange of OLA with DT on the stability is also shown. PMAA in the coating provided a significant blue shift in the peak maxima, enhanced the luminescence intensity, and, most importantly, improved the long-term stability of QDs, especially in liquid petroleum products (oil, gasoline, and diesel). Such stability and size tunability was utilized to create binary barcodes. Hence, these QDs are shown as promising luminescent nanotags for liquid petroleum products. The development of such stable QD-based nanotags offers an invaluable use of nanotechnology for optical barcode generation.Publication Open Access Magnetic iron oxide nanoparticles as long wavelength photoinitiators for free radical polymerization(Royal Society of Chemistry (RSC), 2015) Dadashi-Silab, Sajjad; Yagci, Yusuf; N/A; Department of Chemistry; Yar, Yasemin; Acar, Havva Funda Yağcı; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 178902Iron oxide nanoparticles (Fe3O4 NPs) capped with lauric acid agents were synthesized and their photocatalytic activity was investigated in free radical photopolymerization of vinyl monomers. These NPs were able to release charge carriers (electron-hole pairs) upon photoexcitation through which the capping agents or an additional amine co-initiator acting as the hole acceptor underwent oxidation to eventually form the initiating radicals. In lauric acid coated Fe3O4 NPs, electron transfer followed by a decarboxylation process accounts for the initiation.Publication Open Access Magnetofection of green fluorescent protein encoding DNA-bearing polyethyleneimine-coated superparamagnetic iron oxide nanoparticles to human breast cancer cells(American Chemical Society (ACS), 2019) Zuvin, Merve; Koşar, Ali; Gözüaçık, Devrim; Kutlu, Özlem; Kaya, Veysel Oğulcan; Kuruoğlu, Efe; Department of Chemistry; Acar, Havva Funda Yağcı; Ünal, Özlem; PhD Student; Department of Chemistry; Graduate School of Sciences and Engineering; 178902; N/AGene therapy is a developing method for the treatment of various diseases. For this purpose, the search for nonviral methods has recently accelerated to avoid toxic effects. A strong alternative method is magnetofection, which involves the use of superparamagnetic iron oxide nanoparticles (SPIONs) with a proper organic coating and external magnetic field to enhance the localization of SPIONs at the target site. In this study, a new magnetic actuation system consisting of four rare-earth magnets on a rotary table was designed and manufactured to obtain improved magnetofection. As a model, green fluorescent protein DNA-bearing polyethyleneimine-coated SPIONs were used. Magnetofection was tested on MCF7 cells. The system reduced the transfection time (down to 1 h) of the standard polyethyleneimine transfection protocol. As a result, we showed that the system could be effectively used for gene transfer.Publication Open Access Meso-2,3-dimercaptosuccinic acid: from heavy metal chelation to CdS quantum dots(Royal Society of Chemistry (RSC), 2012) Özen, Can; N/A; Department of Chemistry; Sevinç, Esra; Ertan, Fatoş Sibel; Ulusoy, Gülen; Acar, Havva Funda Yağcı; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902DMSA (meso-2,3-dimercaptosuccinic acid) a prescription drug and a heavy-metal chelating agent, is shown to act both as a sulfur source and a capping agent in the aqueous synthesis of CdS quantum dots under mild conditions. Release of sulfur from DMSA depends on the solution pH and the reaction temperature. Combination of 70 C and pH 7.5 was determined as the best reaction conditions for a well-controlled reaction. Changing the SH/Cd ratio from 2.5 to 7 provides QDs emitting from blue to orange with 6–9% quantum yield with respect to Rhodamine 2B. Viability tests performed with HeLa and MCF-7 cell lines indicate a very low cytotoxicity. Mild reaction conditions and biocompatibility makes these particles valuable candidates for bio applications.Publication Open Access One-step aqueous synthesis of anionic and cationic AgInS2 quantum dots and their utility in improving the efficacy of ALA-based photodynamic therapy(American Chemical Society (ACS), 2022) Loizidou, Marilena; MacRobert, Alexander J.; Department of Chemistry; Acar, Havva Funda Yağcı; Hashemkhani, Mahshid; PhD Student; Department of Chemistry; College of Sciences; Graduate School of Sciences and Engineering; 178902; N/ASilver-indium-sulfide quantum dots (AIS QDs) have potential applications in many areas, including biomedicine. Their lack of regulated heavy metals, unlike many commercialized QDs, stands out as an advantage, but the necessity for alloyed or core-shell structures and related costly and sophisticated processes for the production of stable and high quantum yield aqueous AIS QDs are the current challenges. The present study demonstrates the one-step aqueous synthesis of simple AgInS2 QD compositions utilizing for the first time either a polyethyleneimine/2-mercaptopropionic acid (AIS-PEI/2MPA) mixture or only 2-mercaptopropionic acid (AIS-2MPA) as the stabilizing molecules, providing a AgInS2 portfolio consisting of cationic and anionic AIS QDs, respectively, and tuneable emission. Small AIS QDs with long-term stability and high quantum yields (19-23%) were achieved at a molar ratio of Ag/In/S 1/10/10 in water without any dopant or a semiconductor shell. The theranostic potential of these cationic and anionic AIS QDs was also evaluated in vitro. Non-toxic doses were determined, and fluorescence imaging potential was demonstrated. More importantly, these QDs were electrostatically loaded with zwitterionic 5-aminolevulinic acid (ALA) as a prodrug to enhance the tumor availability of ALA and to improve ALA-induced porphyrin photodynamic therapy (PDT). This is the first study investigating the influence of nanoparticle charge on ALA binding, release, and therapeutic efficacy. Surface charge was found to be more critical in cellular internalization and dark toxicity rather than drug loading and release. Both QDs provided enhanced ALA release at acidic pH but protected the prodrug at physiological pH, which is critical for tumor delivery of ALA, which suffers from low bioavailability. The PDT efficacy of the ALA-loaded AIS QDs was tested in 2D monolayers and 3D constructs of HT29 and SW480 human colon adenocarcinoma cancer cell lines. The incorporation of ALA delivery by the AIS QDs, which on their own do not cause phototoxicity, elicited significant cell death due to enhanced light-induced ROS generation and apoptotic/necrotic cell death, reducing the IC50 for ALA dramatically to about 0.1 and 0.01 mM in anionic and cationic AIS QDs, respectively. Combined with simple synthetic methods, the strong intracellular photoluminescence of AIS QDs, good biocompatibility of especially the anionic AIS QDs, and the ability to act as drug carriers for effective PDT signify that the AIS QDs, in particular AIS-2MPA, are highly promising theranostic QDs.Publication Open Access Phosphonic acid-functionalized poly(amido amine) macromers for biomedical applications(Wiley, 2020) Altuncu, Seçkin; Akyol, Ece; Güven, Melek Naz; Avcı, Duygu; N/A; Department of Chemistry; Demirci, Gözde; Acar, Havva Funda Yağcı; Master Student; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 178902Novel phosphonic acid-functionalized poly(amido amine) (PAA) macromers are synthesized through aza-Michael addition of 2-aminoethyl phosphonic acid or its mixture with 5-amino-1-pentanol at different ratios onto N,N '-methylene bis(acrylamide) to control the amount of phosphonic acid functionality. The macromers were homo- and copolymerized with 2-hydroxyethyl methacrylate at different ratios to obtain hydrogels with various hydrophilicities. The hydrogels' swelling, biodegradation and mineralization properties were evaluated. The swelling and degradation rates of the gels can be tuned by the chemical structure of PAA macromer precursors as well as pH and CaCl2 pre-treatment. The hydrogels show composition-dependent mineralization in SBF and 5xSBF, as evidenced from Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analyses. The degradation products of the hydrogels have no effect on U-2 OS, Saos-2 and NIH 3T3 cells, suggesting their cytocompatibility. Overall, these materials have potential to be used as nontoxic degradable biomaterials.Publication Open Access Recent advances in cyanine-based phototherapy agents(Frontiers, 2021) N/A; Department of Chemistry; Bilici, Kübra; Çetin, Sultan; Çelikbaş, Eda; Acar, Havva Funda Yağcı; Kölemen, Safacan; PhD Student; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902; 272051Phototherapies, in the form of photodynamic therapy (PDT) and photothermal therapy (PTT), are very promising treatment modalities for cancer since they provide locality and turn-on mechanism for toxicity, both of which are critical in reducing off-site toxicity. Irradiation of photosensitive agents demonstrated successful therapeutic outcomes; however, each approach has its limitations and needs to be improved for clinical success. The combination of PTT and PDT may work in a synergistic way to overcome the limitations of each method and indeed improve the treatment efficacy. The development of single photosensitive agents capable of inducing both PDT and PTT is, therefore, extremely advantageous and highly desired. Cyanine dyes are shown to have such potential, hence have been very popular in the recent years. Luminescence of cyanine dyes renders them as phototheranostic molecules, reporting the localization of the photosensitive agent prior to irradiation to induce phototoxicity, hence allowing image-guided phototherapy. In this review, we mainly focus on the cyanine dye-based phototherapy of different cancer cells, concentrating on the advancements achieved in the last ten years.Publication Open Access RGDS-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles enhance specific intracellular uptake by HeLa cells(Dove Medical Press, 2012) N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Nazlı, Caner; Ergenç, Tuğba İpek; Yar, Yasemin; Acar, Havva Funda Yağcı; Kızılel, Seda; PhD Student; Undergraduate Student; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902; 28376The objective of this study was to develop thin, biocompatible, and biofunctional hydrogel-coated small-sized nanoparticles that exhibit favorable stability, viability, and specific cellular uptake. This article reports the coating of magnetic iron oxide nanoparticles (MIONPs) with covalently cross-linked biofunctional polyethylene glycol (PEG) hydrogel. Silanized MIONPs were derivatized with eosin Y, and the covalently cross-linked biofunctional PEG hydrogel coating was achieved via surface-initiated photopolymerization of PEG diacrylate in aqueous solution. The thickness of the PEG hydrogel coating, between 23 and 126 nm, was tuned with laser exposure time. PEG hydrogel-coated MIONPs were further functionalized with the fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) sequence, in order to achieve a biofunctional PEG hydrogel layer around the nanoparticles. RGDS-bound PEG hydrogel-coated MIONPs showed a 17-fold higher uptake by the human cervical cancer HeLa cell line than that of amine-coated MIONPs. This novel method allows for the coating of MIONPs with nano-thin biofunctional hydrogel layers that may prevent undesirable cell and protein adhesion and may allow for cellular uptake in target tissues in a specific manner. These findings indicate that the further biofunctional PEG hydrogel coating of MIONPs is a promising platform for enhanced specific cell targeting in biomedical imaging and cancer therapy.Publication Open Access Synergistic effect of plasmonic gold nanoparticles decorated carbon nanotubes in quantum Dots/TiO2 for optoelectronic devices(Wiley, 2020) Selopal, Gurpreet Singh; Mohammadnezhad, Mahyar; Besteiro, Lucas, V.; Liu, Jiabin; Zhang, Hui; Navarro-Pardo, Fabiola; Liu, Guiju; Wang, Maorong; Sun, Shuhui; Zhao, Haiguang; Wang, Zhiming M.; Department of Chemistry; N/A; Acar, Havva Funda Yağcı; Çavuşlar, Özge; Durmuşoğlu, Emek Göksu; Faculty Member; Department of Chemistry; College of Sciences; Graduate School of Sciences and Engineering; 178902; N/A; N/AHere, a facile approach to enhance the performance of solar-driven photoelectrochemical (PEC) water splitting is described by means of the synergistic effects of a hybrid network of plasmonic Au nanoparticles (NPs) decorated on multiwalled carbon nanotubes (CNTs). The device based on TiO2–Au:CNTs hybrid network sensitized with colloidal CdSe/(CdSexS1−x)5/(CdS)1 core/alloyed shell quantum dots (QDs) yields a saturated photocurrent density of 16.10 ± 0.10 mA cm−2 [at 1.0 V vs reversible hydrogen electrode (RHE)] under 1 sun illumination (AM 1.5G, 100 mW cm−2), which is ≈26% higher than the control device. The in-depth mechanism behind this significant improvement is revealed through a combined experimental and theoretical analysis for QDs/TiO2–Au:CNTs hybrid network and demonstrates the multifaceted impact of plasmonic Au NPs and CNTs: i) hot-electron injection from Au NPs into CNTs and TiO2; ii) near-field enhancement of the QDs absorption and carrier generation/separation processes by the plasmonic Au NPs; iii) enhanced photoinjected electron transport due to the highly directional pathways offered by CNTs. These results provide fundamental insights on the properties of QDs/TiO2–Au:CNTs hybrid network, and highlights the possibility to improve the performance of other solar technologies.Publication Open Access Synthesis of stable gold nanoparticles using linear polyethyleneimines and catalysis of both anionic and cationic azo dye degradation(Royal Society of Chemistry (RSC), 2020) Abkenar, Sirous Khabbaz; Ow-Yang, Cleva W.; N/A; Department of Chemistry; Çavuşlar, Özge; Acar, Havva Funda Yağcı; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902Reduction of auric acid with polyethyleneimine (PEI) provides a simple, low-cost alternative for the production of cationic gold nanoparticles (GNPs). However, linear PEI (lPEI) failed to produce small, colloidally stable GNPs, so far. Since lPEI is a polyelectrolyte, pH should be an important factor both in reduction and stabilization of GNPs and may be optimized to produce small and stable lPEI/GNPs. Cationic GNPs were produced by the direct reduction of auric acid in water with lPEI utilizing two different methods to dissolve the polymer: by protonation or at high temperature. The influence of pH on the particle formation and properties was studied over a wide pH range (3.5 to 10). The impacts of the PEI/Au mass ratio, polymer molecular weight (2.5 and 25 kDa) and post-synthetic pH on the particle properties were also studied. Best is to dissolve lPEI by protonation and to clean the GNPs via controlled centrifugal precipitation. The MW did not influence the hydrodynamic size, stability or particle shape, but low MW lPEI provided faceted particles. This simple one pot synthesis of small, stable cationic GNPs in water is a valuable, simple alternative for producing new cationic GNPs with even low molecular weight lPEI. Additionally, these GNPs were evaluated as catalysts in the degradation of methyl orange (MO) (anionic-zwitterionic) and methylene blue (MB) (cationic) azo dyes at different pH values. The fastest degradation of MO and MB was recorded at pH 7.5 and 3.5, respectively. Overall, this is a rare case where a single catalyst quickly and effectively catalyzes the degradation of both cationic and anionic dyes.Publication Open Access Targeting of epidermal growth factor receptor (EGFR)-positive pancreatic cancer cell lines with cetuximab-conjugated near-infrared silver sulphide quantum dots(Society of Photo-optical Instrumentation Engineers (SPIE), 2019) Labib, Peter L.; Yaghini, Elnaz; Davidson, Brian R.; MacRobert, Alexander J.; Loizidou, Marilena; Pereira, Stephen P.; N/A; Department of Chemistry; Hashemkhani, Mahshid; Acar, Havva Funda Yağcı; PhD Student; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 178902Introduction: fluorescence-guided surgery could potentially reduce local recurrence after pancreatic cancer resection. However, the ideal contrast agent for this purpose is not yet determined. The monoclonal antibody cetuximab targets the EGFR receptor, which is overexpressed in 64% of pancreatic cancers. We investigated the efficacy of near-infrared emitting silver sulphide Quantum Dot (QD)-cetuximab nanoconjugates for targeting EGFR-positive pancreatic cancer. Methods: 2-Mercaptopropionic acid-coated QDs were prepared from AgNO3 and Na2S. Pancreatic cancer cell lines PANC-1 and CFPAC-1 were confirmed EGFR-positive using a commercial AlexaFluor488-cetuximab probe. Nonconjugated QD and cetuximab-conjugated QD (QD-cetuximab) toxicity was assessed after 24 and 48 hours using MTT assay. Fluorescence microscopy was performed following a) formaldehyde-fixed immunofluorescence and b) live staining with QD-cetuximab for four hours at concentrations corresponding to 0, 10, 50, 100, 200, 400 and 600μg ml-1 of silver. Results: untargeted QDs were non-toxic in both cell lines after 48 hours at all investigated concentrations, whereas QDcetuximab was toxic at 100μg ml-1 after 24 hours in PANC-1 and at 10μg ml-1 in CFPAC-1. Fixed immunofluorescence demonstrated EGFR targeting by QD-cetuximab at concentrations of 50μg ml-1 upwards in both cell lines. Live staining demonstrated similar efficacy of EGFR targeting up to 50μg ml-1, although a reduction of fluorescence at higher concentrations was observed when compared to fixed immunofluorescence. Conclusion: silver sulphide QD-cetuximab nanoconjugates have the potential to target live EGFR-positive pancreatic cancer cells at doses of up to 50 μg ml-1. The reduction in QD fluorescence observed at higher concentrations is likely to be secondary to cetuximab toxicity.