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Öğe Micro and Nanogels for Biomedical Applications(Hacettepe Üniversitesi, Fen Fakültesi, 2020) Can, Mehmet; Güven, Olgun; Şahiner, NurettinMicro and nano hydrogels developed from natural and synthetic polymers have garnered great deal of attention in scientific and industrial realms due to their higher surface area, degree of swelling and active material loading capacity,softness and flexibility, as well as their similarity to natural tissues. Particularly, biocompatible, non-toxic, and biodegradable micro/nano vehicles with tailor made design and functionalization facilitates their use with excellent feasibility for a variety of biomedical applications such as tissue engineering, bioimaging and drug delivery. However, these platforms requirerational design and functionalization strategies to cope with barriers of in vivo environment to pass into clinical use. Firstly,an ideal carrier should be biocompatible, and capable of evasion from immune elimination, specifically target at desiredsites and sustainably release the therapeutic cargo in response to microenvironment conditions. Despite the few setbacksin micro/nano vehicle design and several successful formulations translated to clinical use and majority of the carries areyet to achieve complete success for all biological criteria. In this review, design and functionalization strategies of micro andnanogels have been summarized. Also, the recent progress in biomedical applications of microgels and nanogels have beenoutlined with a primary focus placed on drug and biomolecule delivery applications.Öğe Nanogel synthesis by irradiation of aqueous polymer solutions(Springer, 2021) Sütekin, S. Duygu; Güven, Olgun; Şahiner, NurettinNanogels/microgels are intramolecularly crosslinked particles with submicron diameters that can swell in a suitable solvent due to their three-dimensional network structure. Nanogels provide beneficial features such as flexibility, biocompatibility, high stability and swelling, fixed shape, large surface/volume ratio, fast stimuli-responsive behavior, etc. Therefore, there is growing interest to further elaborate nanogel formulations in preclinical applications as therapeutics, diagnostics, or nanosensors. However, conventional nanogel synthesis methods may end up with nanogels containing toxic residuals, e.g., initiator, crosslinking agent, and fragments which possess a major disadvantage in biomedical applications requiring tedious purification steps. This chapter reviews the synthesis of nanogels by irradiation of dilute aqueous polymer solutions to induce intramolecular crosslinking by gamma rays or accelerated electrons. This simple, ecofriendly, and cost-effective manufacturing method eliminates the purification step and provides the possibility to produce clean nanogels with desired sizes at room temperature. In the formation of nanogels, the degree of crosslinking can be controlled by polymer solution properties as well as operational parameters such as dose rate of radiation source and total absorbed dose. The method can be applied to many water-soluble polymers, copolymers, or interpolymer complexes for the development of nanogels with desired sizes and properties.Öğe P(HMA-co-ATU) hydrogel synthesis via gamma radiation and its use for in situ metal nanoparticle preparation and as catalyst in 4-nitrophenol reduction(Pergamon-Elsevier Science Ltd, 2022) Güven, Olgun; Demirci, Şahin; Sütekin, S. Duygu; Ari, Betül; Şahiner, NurettinHydrogels with reactive thiourea functional groups were prepared by radiation-induced crosslinking of N-(Hydroxymethyl) acrylamide (HMA) and N-allyl thiourea (ATU) at different ATU content and irradiation doses. P (HMA-co-ATU) hydrogels were then utilized as template for in situ metal nanoparticle (MNP) preparation by the reduction of Ni2+, Co2+, and Cu(2+)ions within the hydrogel matrix using sodium borohydride (NaBH4) as reducing agent. These MNP@p(HMA-co-ATU) hydrogel composites (MNP = Co, Ni, and Cu) were further used as catalysts in the reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (AP). Various parameters such as the effect of ATU content, the total dose used in the hydrogel preparation, MNPs type, and temperature on the catalytic activity of hydrogel composites were investigated. The activation energy, enthalpy, and entropy of Ni@p(HMA-co-ATU) hydrogels for the reduction reaction of 4-NP to 4-AP were calculated as 42.5 kJ mol-1, 38.9 kJ mol(-1), and-187.3 J mol(-1) K-1, respectively.Öğe Poly(2-aminoethyl methacrylate) based microgels catalyst system to be used in hydrolysis and methanolysis of NaBH4 for H2 generation(Elsevier Ltd, 2023) Demirci, Şahin; Sutekin, S. Duygu; Güven, Olgun; Şahiner, NurettinThe poly(2-aminoethyl methacrylate) (p(AEM)) microgels were synthesized by microemulsion polymerization technique and used for in situ metal nanoparticle preparation to render as p(AEM)-M (M: Co or Ni) microgel composites and were used in p(AEM) based poly ionic liquid (PIL) microgels. Next, these p(AEM)) based microgel materials were used as catalysts for hydrogen (H2) production from both hydrolysis and methanolysis reactions of sodium borohydride (NaBH4). It was found that the catalytic hydrolysis of the NaBH4 reaction, catalyzed by p(AEM)-Co microgel composite was completed in 140 min, whereas the methanolysis of NaBH4 methanolysis catalyzed by the PIL of p(AEM)+Cl− microgels was completed in 5 min both with 250 ± 2 mL H2 production. Furthermore, p(AEM)-Co microgel composite catalysts maintained 80% catalytic activity after 5 consecutive uses in NaBH4 hydrolysis. On the other hand, p(AEM)+Cl− microgels were found to afford more than 50% catalytic activity even after 20 repetitive use in NaBH4 methanolysis due to superior regeneration ability. Moreover, activation energy values for p(AEM)-Co microgel composites catalyzed NaBH4 hydrolysis reaction were calculated as 38.9 kJ/mol in comparison to 37.3 kJ/mol activation energy of p(AEM)+Cl− microgel catalyzed methanolysis reaction.Öğe Poly(vinyl amine) microparticles derived from N-Vinylformamide and their versatile use(Springer Science and Business Media Deutschland GmbH, 2022) Demirci, Şahin; Sutekin, S. Duygu; Kurt, Saliha B.; Güven, Olgun; Şahiner, NurettinCationic polymers with primary amine groups that can easily be functionalized or coupled with substrates by complexation or hydrogen bonding are especially advantageous in preparing particles for biomedical applications. Poly(vinyl amine) (PVAm) is a cationic polyelectrolyte containing the highest number of primary amine groups among any other polymers. Here, we introduce a general method in synthesizing PVAm microparticles via a surfactant-free water-in-oil emulsion technique using cyclohexane as the oil phase and aqueous PVAm solution as the dispersed phase. PVAm particles were prepared to employ two different bifunctional chemical crosslinkers, divinyl sulfone (DVS) and poly(ethylene glycol) diglycidyl ether (PEGGE). The prepared particles were further treated with HCl to protonate the amine groups of PVAm within particles. The effect of crosslinker types and pH on the hydrolytic degradation of PVAm particles were also investigated at three different solution pHs, 5.4, 7.4, and 9, to simulate the skin, blood, and intestinal pH environments, respectively. The blood compatibility of the PVAm particles was evaluated by in vitro hemolysis and blood clotting assays. Furthermore, antifungal and antibacterial efficacy of PVAm-based particles and their protonated forms were tested against C. albicans yeast and E. coli, S. aureus, B. subtilis, and P. aeruginosa bacterial strains.Öğe Poly(Vinylamine) Derived N-Doped C-Dots with Antimicrobial and Antibiofilm Activities(MDPI (Multidisciplinary Digital Publishing Institute), 2021) Sutekin, Semiha Duygu; Şahiner, Mehtap; Suner, Selin Sağbaş; Demirci, Şahin; Güven, Olgun; Şahiner, NurettinNitrogen-doped carbon dots (N-doped C-dots) was synthesized by using poly(vinyl amine) (PVAm) as a nitrogen source and citric acid (CA) as a carbon source via the hydrothermal method. Various weight ratios of CA and PVAm (CA:PVAm) were used to synthesize N-doped C-dots. The N-doped C-dots revealed emission at 440 nm with excitation at 360 nm and were found to increase the fluorescence intensity with an increase in the amount of PVAm. The blood compatibility studies revealed no significant hemolysis for N-doped C-dots that were prepared at different ratios of CA:PVAm for up to 500 μg/mL concentration with the hemolysis ratio of 1.96% and the minimum blood clotting index of 88.9%. N-doped C-dots were found to be more effective against Gram-positive bacteria than Gram-negative bacteria, with the highest potency on Bacillus subtilis (B. subtilis). The increase in the weight ratio of PVAm in feed during C-dots preparation from 1 to 3 leads to a decrease of the minimum bactericidal concentration (MBC) value from 6.25 to 0.75 mg/mL for B. subtilis. Antibiofilm ability of N-doped C-dots prepared by 1:3 ratio of CA:PVAm was found to reduce %biofilm inhibition and eradication- by more than half, at 0.78 mg/mL for E. coli and B. subtilis generated biofilms and almost destroyed at 25 mg/mL concentrations.Öğe Tannic acid-based bio-MOFs with antibacterial and antioxidant properties acquiring non-hemolytic and non-cytotoxic characteristics(Elsevier, 2025) Şahiner, Nurettin; Güven, Olgun; Demirci, Şahin; Sağbaş Suner, Selin; Şahiner, Mehtap; Arı, Betül; Can, MehmetTannic acid (TA) based bio-metal phenolic networks (bio-MPNs) were prepared by using Cu(II), Zn(II), Bi(III), Ce(III), La(III), and Ti(IV) metal ions. TA-based bio-MPNs exhibited wedge-shaped pores between 16.4 and 25.8 nm pore size ranges. The higher gravimetric yield% was achieved for TA-Bi(III), and TA-Ti(IV) bio-MPNs with more than 90 %, and higher surface area was observed for TA-La(IIII) bio-MPNs as 56.2 m(2)/g with 17.3 nm average pore sizes. All TA-based MPNs are non-hemolytic with less than 5 % hemolysis ratio, whereas TA-based Bio-MPNs do not affect blood clotting with > 90 % blood clotting indexes except for TA-Cu(II) Bio-MPNs at 0.1 mg/mL concentration. Moreover, TA-Bi(III) and TA-Ce(III) Bio-MPNs were found to be safer materials showing no significant toxicity on L929 fibroblast cells at 100 mu g/mL concentration, along with TA-based Bio-MPNs prepared with Cu(II), Zn(II), La(III), and Ti(IV) metal ions that could be safely used in in vivo applications at 1 mu g/mL concentration. It has been proven by 2 different antioxidant tests that the prepared TA-based Bio-MPNs show antioxidant properties even if their TA-derived antioxidant properties decrease. Furthermore, all types of TA-based Bio-MPNs show great antimicrobial activity depending on the metal ion or microorganism types and the highest antibacterial/antifungal effect was determined for TA-Cu(II), and TA-Zn(II) Bio-MPNs with the lowest MBC/MFC values against Pseudomonas aeruginosa ATCC 10145, Bacillus subtilis ATCC 6633, and Candida albicans ATCC 10231.Öğe The Preparation of p acrylonitrile-co- acrylamide hydrogels for uranyl ion recovery from aqueous environments(Hacettepe Üniversitesi, 2014) Alpaslan, Duygu; Aktaş, Nahit; Yılmaz, Selehattin; Şahiner, Nurettin; Güven, OlgunThe synthesis of poly acrylonitrile-co-acrylamide p AN-co-AAm hydrogels with different amounts of acrylonitrile AN and acrylamide AAm monomers were carried out by concurrent use of redox and microemulsion polymerization techniques. The prepared hydrogels were amidoximated for sorption of uranyl ion from aqueous medium. Batch type UO2 2+ ion sorption by p AN-co-AAm 0.25:1 mole ratio was carried out and an sorption capacity of 220 mg UO2 2+ mg/g dried hydrogel was found. The highest amount of UO22+ ion sorption, 277 mg/g dry gel was accomplished at pH 4Öğe The Preparation of p(acrylonitrile-coacrylamide) hydrogels for uranyl ion recovery from aqueous environments(2014) Alpaslan, Duygu; Aktaş, Nahit; Yılmaz, Selehattin; Şahiner, Nurettin; Güven, OlgunThe synthesis of poly(acrylonitrile-co-acrylamide) (p(AN-co-AAm)) hydrogels with different amounts of acrylonitrile (AN) and acrylamide (AAm) monomers were carried out by concurrent use of redox and microemulsion polymerization techniques. The prepared hydrogels were amidoximated for sorption of uranyl ion from aqueous medium. Batch type $UO_2^{2+}$ ion sorption by p(AN-co-AAm) (0.25:1 mole ratio) was carried out and an sorption capacity of 220 mg $UO_2^{2+}$ mg/g dried hydrogel was found. The highest amount of UO22+ ion sorption, 277 mg/g dry gel was accomplished at pH 4.Öğe Tunable fluorescent and antimicrobial properties of poly(vinyl amine) affected by the acidic or basic hydrolysis of poly(N-vinylformamide)(Wiley, 2021) Demirci, Şahin; Kurt, Saliha B.; Güven, Olgun; Şahiner, Nurettin; Sütekin, S. DuyguSynthesis of poly(N-vinylformamide) (PNVF) and its subsequent hydrolysis toconvert it to poly(vinyl amine) (PVAm) were performed. Kinetics of acidic andbasic hydrolysis of poly(N-vinylformamide) (PNVF), and products of hydroly-sis were investigated by using Fourier transform infrared, size exclusion chro-matography,1H NMR, and13C NMR spectroscopies, and thermogravimetricanalysis. It was observed that amide groups did not completely transform intoamine groups by acidic hydrolysis of PNVF while the conversion of amidesinto amine groups via basic hydrolysis of PNVF was complete in 12 h, as con-firmed by spectroscopic measurements. Results of extensive characterizationrevealed significant structural and conformational differences between acidicand basic hydrolysis products. Fluorescence spectroscopy was used for the firsttime to follow the conversion of amide groups into amine groups. The fluores-cence intensity of PVAm obtained from basic hydrolysis of PVNF showed sig-nificant increase with amide/amine conversion. Finally, PVAm obtained fromacidic hydrolysis of PNVF demonstrated potent antimicrobial activity, 10–20times more, against common pathogens for example,C. albicans asfungalstrain andE. coli,S. aureus,B. subtilis,andP. aeruginosaas bacterial strains ascompared to PVAm obtained from basic hydrolysis.
