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Biocompatible poly(galacturonic acid) micro/nanogels with controllable degradation via tunable chemical crosslinking
(Elsevier, 2022) Sağbaş Suner, Selin; Ari, Betül; Sutekin, S. Duygu; Şahiner, Nurettin
Here, one-pot labor-less preparation of two different polygalacturonic acid (PGA) micro/nanogel formulations, PGA-1 and PGA-2, by respectively crosslinking the PGA chains with divinyl sulfone (DVS) and trimethylolpmpane triglycidyl ether (TMPGDE) were reported. Various crosslinker ratios, 2.5, 10, 50, and 100% were used for both crosslinkers to demonstrate the tunability of their degradation properties. The PGA micro/nanogels were found spherical-shaped porous particles in 0.5-5.0 mu m size range by SEM. The hydrolytic degradation and stability of PGA micro/nanogels in pH 1.0, 7.4, and 9.0 buffer solutions can be controlled by changing the degree of crosslinking. Accordingly, 32 +/- 8% and 36 +/- 2% weight losses were attained for PGA-1-10% and PGA-2-10% micro/nanogels at pH 1, respectively, and 46 +/- 6%, and 68 +/- 6% degradations were determined at pH 7.4 within 4 weeks. However, no degradation was observed for both PGA-based micro/nanogel formulations prepared at 25% and 100% crosslinker ratios at all pH conditions. All PGA-based micro/nanogels were totally degraded within 7-10 days at pH 9.0. In the presence of pectinase and amyloglucosidase enzymes, all formulations of PGA micro/nanogels showed more than 80% degradation within 12 h. Furthermore, both PGA formulations showed no significant cytotoxicity against L929 fibroblast cells with 90% and above cell viability up to 250 mg/mL concentrations.
Biodegradable super porous inulin cryogels as potential drug carrier
(Wiley, 2020) Ari, Betül; Şahiner, Nurettin
Here, chemically crosslinked super porous inulin cryogels were synthesized by the cryogelation method using divinyl sulfone (DVS) at various mol ratios of 75% to 150% inulin repeating units. Inulin cryogel prepared at 75 mol% DVS crosslinking showed a maximum swelling capacity of 1842 +/- 159% in phosphate buffer saline (PBS, pH 7.4). The hydrolytic degradation of inulin cryogels prepared at different ratios were investigated at 37.5 degrees Cat pH 1, 7.4, and 9. Depending on the degree of crosslinking, it was found that inulin cryogels were completely degraded in 1 to 6 days at pH 1, and the degradation continued at pH 7.4 and 9 for up to 21 days. Inulin cryogel with 75 mol% crosslinker had 61% +/- 7% and 45% +/- 2% weight losses at pH 7.4 and pH 9, respectively, at end of 21 days. Also, 75% crosslinked inulin cryogel was conjugated with amoxicillin trihydrate (AMX) drug and released 65.15 +/- 5.35 mg/g of AMX at pH 1 at end of 24 hours. At pH 7.4 and 9, the AMX released amount were determined as 64.83 +/- 6.19 and 55.57 +/- 4.00 mg/g, respectively, in 120 hours. Furthermore, inulin cryogels were determined to be blood compatible materials via hemolytic tests with hemolysis ratio of 1.08% +/- 0.14% and a blood clotting index of 80.67% +/- 1.86%.
Boric acid versus boron trioxide as catalysts for green energy source H2 production from sodium borohydride methanolysis
(2021) Demirci, Şahin; Ari, Betül; Bütün Şengel, Sultan; İnger, Erk; Şahiner, Nurettin
Here, boric acid (H3BO3) and its dewatered form, boron trioxide (B2O3) were tested as catalysts for hydrogen (H2) evolution in the methanolysis of sodium borohydride (NaBH4) in methanol. Parameters such as catalyst types and their amounts, NaBH4 concentration, and the reaction temperature affecting the hydrogen generation rate (HGR) were studied. It has been found that H3BO3 and B2O3 catalyzed methanolysis reaction of NaBH4 follow up first-order kinetics relative to the concentration of NaBH4. Furthermore, the conversion and activity of these catalysts were examined to determine their performance in ten consecutive use. Interestingly, H3BO3 and B2O3 have demonstrated superior catalytic performances in methanolysis of NaBH4 comparing to the studies published in literature with the activation energy of respectively 22.08 kJ.mol-1, and 23.30 kJ.mol-1 in H2 production. The HGR was calculated as 6481 mL.min-1.g-1 and 5163 mL.min-1.g-1 for H3BO3 and B2O3 catalyst, respectively for 50 mg catalyst at 298 K. These results are comparably better than most metal nanoparticle catalysts used for H2 production in addition to the naturally occurring boron-based environmentally friendliness of these materials.
Chondroitin Sulfate-Based Cryogels for Biomedical Applications
(MDPI, 2021) Demirci, Şahin; Şahiner, Mehtap; Ari, Betül; Sunol, Aydın K.; Şahiner, Nurettin
Cryogels attained from natural materials offer exceptional properties in applications such as tissue engineering. Moreover, Halloysite Nanotubes (HNT) at 1:0.5 weight ratio were embedded into CS cryogels to render additional biomedical properties. The hemolysis index of CS cryogel and CS:HNT cryogels was calculated as 0.77 ± 0.41 and 0.81 ± 0.24 and defined as non-hemolytic mate-rials. However, the blood coagulation indices of CS cryogel and CS:HNT cryogels were determined as 76 ± 2% and 68 ± 3%, suggesting a mild blood clotting capability. The maximum% swelling capacity of CS cryogel was measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, at pH 1.0, pH 7.4 and pH 9.0, respectively, which were reduced to 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, for CS:HNT cryogel. It was found that CS cryogels can hydrolytically be degraded 41 ± 1% (by wt) in 16-day incubation, whereas the CS:HNT cryogels degraded by 30 ± 1 wt %. There is no chelation for HNT and 67.5 ± 1% Cu(II) chelation for linear CS was measured. On the other hand, the CS cryogel and CS:HNT cryogel revealed Cu(II) chelating capabilities of 60.1 ± 12.5%, and 43.2 ± 17.5%, respectively, from 0.1 mg/mL Cu(II) ion stock solution. Additionally, at 0.5 mg/mL CS, CS:HNT, and HNT, the Fe(II) chelation capacity of 99.7 ± 0.6, 86.2 ± 4.7% and only 11.9 ± 4.5% were measured, respectively, while no Fe(II) was chelated by linear CS chelated Fe(II). As the adjustable and con-trollable swelling properties of cryogels are important parameters in biomedical applications, the swelling properties of CS cryogels, at different solution pHs, e.g., at the solution pHs of 1.0, 7.4 and 9.0, were measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, respectively, and the maximum selling% values of CS:HNT cryogels were determined as 1961 ± 288%, 2816 ± 192, 2405 ± 73%, re-spectively, at the same conditions. Alpha glucosidase enzyme interactions were investigated and found that CS-based cryogels can stimulate this enzyme at any CS formulation.
Dekstran Kriyojellerinin Hazırlanması ve Bunların Bazı Uygulamaları
(Çanakkale Onsekiz Mart Üniversitesi, 2019) Ari, Betül; Sahiner, Nurettin
Bu çalışmada, dekstran (DEX) kriyojeleri, tekrarlayan DEX birimine göre %50 divinil sülfon (DVS) çapraz bağlayıcı kullanılarak kriyojenik koşullar altında kriyojelasyon tekniği ile hazırlanmıştır. DEX kriyojellerinin çevreye ve insan sağlığına zararlı organik boya, metilen mavisi (MB), pestisit, parakuat (PQ) gibi toksik maddeleri uzaklaştırmak için kolon dolgu maddesi olarak kullanılabileceği gösterilmiştir. DEX kriyojelinin 15 mg’ı için maksimum absorpsiyon kapasitesine, MB için yaklaşık yedi dakikada 5 mL-100 ppm çözeltiden 10,69±0,14 mg/g, PQ için ise yaklaşık on dakikada 2,87±0,33 mg/g absorblayarak ulaşmıştır. DEX kriyojelinin MB için yeniden kullanılabilirliği de yapılmıştır. ~30 mg ağırlığındaki DEX kriyojelinin art arda kullanımında, başlangıçta 20 ppm, 30 mL olan MB çözeltisinden absorplanan miktar 6,43±0,15 mg MB/g kriyojel olarak hesaplanmış, bu değer beşinci kullanımdan sonra 4,71±0,48 mg MB/g kriyojel olarak hesaplanmıştır. MB absorplamış DEX kriyojeli ile yapılan salım çalışmalarında ilk kullanımda 3,78±0,33 mg MB/g kriyojel salmıştır, ancak beşinci kullanımdan sonra, salınan miktar, 1 M 30 mL HC1 ile muamele üzerine 0,92±0,38 mg MB/g kriyojel olarak hesaplanmıştır. DEX kriyojelinin MB için adsorpsiyon kinetiği de incelenmiş olunup, 0,9983 korelasyon katsayısı ve 0,36 KL değeri ile Freundlich, Temkin, Elovich ve Dubinin-Radushkevich izotermleri gibi diğer iyi bilinen modeller arasında en uygun olan Langmuir izoterm modelini temsil ettiği belirlenmiştir
Highly re-usable porous carbon-based particles as adsorbents for the development of CO2 capture technologies
(Elsevier Sci Ltd, 2024) Ari, Betül; Sunol, Aydin K.; Şahiner, Nurettin
Combating climate change and global warming focuses generally on eliminating carbon emissions from energy production or transportation. For this purpose, CO2 capture, storage and utilization technologies were developed to remove or uptake carbon from the atmosphere. Here, porous carbon particles (PCPs) were prepared via hydrothermal and carbonization methods from various disaccharides sources, sucrose (S) as S-PCPs, lactose (L) as L-PCPs, and maltose (M) as M-PCPs as adsorbents for CO2 capture. Surface areas, pore volumes, and pore sizes of all adsorbents were determined using the N-2 adsorption-desorption method and as S-PCP is the adsorbent with the highest surface area, 460 m(2)/g exhibited the highest CO2 capture capacity which are 3.58 +/- 0.03 mmol CO2/g absorbent at 273 K and 2.48 +/- 0.02 mmol CO2/g absorbent at 298 K at about 1 atm pressure. Furthermore, S-PCP was found to be practically completely stable for at least 10 successive uses and the adsorption capacity >90 % at the end 10th use. More importantly, S-PCPs can be re-activatable by simple NaOH treatments at the end of 10 times adsorption-desorption cycle via simple NaOH treatment. Here, S-PCP particles after 10 repetitive uses were re-activated and continued to total 15th CO2 adsorption-desorption and CO2 adsorption capacity decreased to only 82 +/- 1.6 % of its first use.
Hyaluronic acid and hyaluronic acid: Sucrose nanogels for hydrophobic cancer drug delivery
(Elsevier Science Bv, 2019) Sağbaş Suner, Selin; Ari, Betül; Cömert Önder, Ferah; Özpolat, Bülent; Ay, Mehmet; Şahiner, Nurettin
Porous and biodegradable hyaluronic acid (HA) nanogel and their copolymeric forms with sucrose (Suc), HA:Sucrose (HA:Suc) nanogels, were synthesized by employing glycerol diglycidyl ether (GDE) as crosslinker with a single step reaction in surfactant-free medium. The size of the nanogels was determined as 150 +/- 50 nm in dried state from SEM images and found to increase to about 540 +/- 47 nm in DI water measured with DLS measurements. The surface areas of HA and HA:Suc nanogels were measured as 18.07 +/- 2.4 and 32.30 +/- 6.1 m(2)/g with porosities of 3.58 +/- 1.8, and 9.44 +/- 3.1 nm via BET analysis, respectively. The zeta potentials for HA and HA:Suc nanogels were measured as -33 +/- 1.4 and -30 +/- 1.2 mV, respectively. The thermal degradation of both types of nanogels revealed similar trends, while hydrolytic degradation of the nanogels was about 22.7 +/- 02 wt% in 15 days. Both HA and HA:Suc nanogels were stable in blood up to 250 mu g/mL concentration with approximately 0.5 +/- 0.1% hemolysis ratio and 76 +/- 12% blood clotting indices, respectively. Finally, these nanogels were used as a sustained slow-release or long-term delivery system over 2 days for a hydrophobic cancer drug, 3-((E)-3-(4-hydroxyphenyl)acryloyl)-2H-chromen-2-on (A(#)) established by our group. The nanogels successfully delivered the model drug A at 10.43 +/- 2.12 mg/g for 2 days. (C) 2019 Elsevier B.V. All rights reserved.
Karragenan, inülin ve dekstran kriyojellerinin hazırlanması ve bunların biyomolekül ayrımında kullanımının araştırılması
(Çanakkale Onsekiz Mart Üniversitesi, 2020) Ari, Betül; Şahiner, Nurettin
Yapılan bu tez çalışması kapsamında doğal polimer olan ?-karragenan, inülin ve dekstranın süpermakro gözenekli kriyojelleri kriyopolimerizasyon tekniği ile sentezlenmiştir. Kriyojeller farklı mol oranlarında çapraz bağlayıcı içerecek şekilde hazırlanmış ve böylece çapraz bağlayıcı miktarının kriyojeller üzerindeki etkisi gösterilmiştir. Sentezlenen kriyojellerin morfolojik analizleri optik mikroskop ve Alan Emisyonlu Taramalı Elektron Mikroskobu (FE-SEM) ile belirlenmiştir. Kriyojellerin yapısal analizleri Fourier Dönüşümlü Kızılötesi Işımalı Spektroskopisik Analizi (FT-IR) ile belirlenmiş olup, termal kararlılıkları Termogravimetrik Analiz (TGA) cihazı kullanılarak gerçekleştirilmiştir. Sentezlenen kriyojellerin, biyomolekül, organik boya ve pestisit gibi yapıları sulu çözeltilerden uzaklaştırma veya ayırma ya da adsorpsiyon çalışmalarında kullanım potansiyelleri araştırılmıştır. Bu bağlamda ?-karragenan, inülin ve dekstran kriyojelleri kullanılarak hemoglobin, whey (WP) ve bovin serum albümin (BSA) proteinleri ve lizozim, pektinaz ve selülaz enzimleri ve L-Arjinin (L-Ar) ve L-Glutamik asit (L-Glu) amino asitleri ve askorbik asit ve riboflavin vitaminleri gibi biyomoleküllerin ve sodyum diklofenak, sülfametaksazol ve trimetoprim ilaçlarının adsorpsiyon çalışmaları yapılmıştır. ?-Karragenan kriyojeli 168,9±15,2 mg/g lizozim, 49,3±18,4 mg/g hemoglobin ve 70,2±1,6 mg/g L-Ar adsorplamıştır. Dekstran kriyojeli 128,1±9,4 mg/g riboflavin adsorplamıştır. İnülin kriyojeli 13,1±7,8 mg/g trimetoprim ve inülin TETA ile modifiye formu yani inülin-TETA kriyojeli 27,5±2,1 mg/g sodyum diklofenak ve 33,7±10,3 mg/g sülfametaksazol ilaçlarını adsorplamıştır. Kriyojellerin boya, pestisit adsorpsiyonu çalışmaları dekstran kriyojelleri kullanılarak yapılmıştır. Dekstran kriyojelleri kullanılarak yapılan metilen mavisi (MM) ve 1'-dimetil-4,4'-bipiridinyum diklorür (parakuat (PK)) boya/pestisit adsorpsiyonu çalışmalarında MM için maksimum adsorpsiyon kapasitesi 10,7±0,1 mg/g ve PK için maksimum adsorpsiyon kapasitesi 2,9±0,3 mg/g olarak hesaplanmıştır. Ayrıca dekstran kriyojelleri için PK ve 2,4-D pestisitleri karıştırılarak yapılan adsorpsiyon çalışmaları sonucunda dağılım katsayısı, seçicilik katsayısı ve uzaklaştırma yüzdeleri hesaplanmıştır. Bu değerler PK için sırasıyla 442±14,8 mL/g, 3,3±0,02 ve % 52,5±7,1 olarak hesaplanmıştır. 2,4-D pestisiti için dağılım katsayısı 132±18,4 mL/g ve uzaklaştırma yüzdesi % 29,2±1,4 olarak hesaplanmıştır. Bunlara ilaveten, amoksisilin trihidrat (AMX) ilacı inülin kriyojeline yüklenmiş ve inülin kriyojellerinin ilaç salım sistemi olarak kullanım potansiyeli araştırılmıştır. Ayrıca tez kapsamında hazırlanan tüm kriyojellerin kan uyumluluğu ve hidrolitik olarak bozunmaları incelenerek biyomedikal alanda kullanım potansiyelleri araştırılmıştır.
Nitrogen Doped Carbon-Dot Embedded Poly(lactic acid-co-glycolic acid) Composite Films for Potential Use in Food Packing Industry and Wound Dressing
(Mdpi, 2022) Şahiner, Mehtap; Ari, Betül; Ram, Manoj K.; Şahiner, Nurettin
Here, nitrogen-doped carbon dots (N-doped CDs) were synthesized by the hydrothermal method embedded within poly(lactic acid-co-glycolic acid) ((PLGA)) films at different amounts. The N-doped CDs (or CD) that possess fluorescence properties also have antimicrobial properties against S. aureus and E. coli microorganisms, determined by the disc diffusion method with 19 +/- 2 and 18 +/- 1 mm zone diameters, respectively. The CD embedded PLGA films (CD@PLGA) with different CD contents revealed an increased fluorescence intensity with the increased amount of CD. Moreover, the antibacterial potency of 50% CD containing PLGA (50-CD@PLGA) films (by weight) against S. aureus and E. coli microorganisms was examined and the zone diameters were found to be 14 +/- 1 and 13 +/- 1 mm, respectively. In addition, CD release studies from different amounts of CD (2.5-50 by weight) containing composite films showed that 50-CD@PLGA film released 127 +/- 16 mg/g CD dots, which is 38 +/- 5% of the embedded CDs in about 12 days, suggesting their potential application in food packing and wound dressing. Moreover, all CD@PLGA films were found to be blood compatible via hemolysis and blood clotting index tests with 90% blood clotting indices regardless of their CD content.
Optimized Porous Carbon Particles from Sucrose and Their Polyethyleneimine Modifications for Enhanced CO2 Capture
(Mdpi, 2024) Ari, Betül; İnger, Erk; Sunol, Aydın K.; Şahiner, Nurettin
Carbon dioxide (CO2), one of the primary greenhouse gases, plays a key role in global warming and is one of the culprits in the climate change crisis. Therefore, the use of appropriate CO2 capture and storage technologies is of significant importance for the future of planet Earth due to atmospheric, climate, and environmental concerns. A cleaner and more sustainable approach to CO2 capture and storage using porous materials, membranes, and amine-based sorbents could offer excellent possibilities. Here, sucrose-derived porous carbon particles (PCPs) were synthesized as adsorbents for CO2 capture. Next, these PCPs were modified with branched- and linear-polyethyleneimine (B-PEI and L-PEI) as B-PEI-PCP and L-PEI-PCP, respectively. These PCPs and their PEI-modified forms were then used to prepare metal nanoparticles such as Co, Cu, and Ni in situ as M@PCP and M@L/B-PEI-PCP (M: Ni, Co, and Cu). The presence of PEI on the PCP surface enables new amine functional groups, known for high CO2 capture ability. The presence of metal nanoparticles in the structure may be used as a catalyst to convert the captured CO2 into useful products, e.g., fuels or other chemical compounds, at high temperatures. It was found that B-PEI-PCP has a larger surface area and higher CO2 capture capacity with a surface area of 32.84 m(2)/g and a CO2 capture capacity of 1.05 mmol CO2/g adsorbent compared to L-PEI-PCP. Amongst metal-nanoparticle-embedded PEI-PCPs (M@PEI-PCPs, M: Ni, Co, Cu), Ni@L-PEI-PCP was found to have higher CO2 capture capacity, 0.81 mmol CO2/g adsorbent, and a surface area of 225 m(2)/g. These data are significant as they will steer future studies for the conversion of captured CO2 into useful fuels/chemicals.
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, Nurettin
Hydrogels 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.
pH-Responsive Amphoteric p (APTMACl-co-AMPS) Hydrogel as Effective Multiple Dye Sponge Network From Aqueous Media
(Frontiers Media Sa, 2022) Demirci, Şahin; Ari, Betül; Aktaş, Nahit; Şahiner, Nurettin
Here, the cationic poly (3-acrylamidepropyl trimethyl ammonium chloride) [p (APTMACl)], anionic poly (2-acrylamido-2methylpropane sulfonic acid) [p (AMPS)], and amphoteric poly (APTMACl-co-AMPS) hydrogels were prepared via free-radical polymerization techniques as pH-sensitive hydrogels. The prepared systems were used in methylene blue (MB), and Eosin Y (EY) removal from aqueous media. HCl-treated p (APTMACl-co-AMPS) hydrogels prepared in 1:3 mol ratio adsorbed higher amount of MB and EY from their corresponding 50 ml 50 ppm aqueous solutions that are 47.5 +/- 0.9, and 10.7 +/- 0.1 mg/g, respectively. Also, the adsorbed amount of MB and EY by HCl-treated p (APTMACl-co-AMPS) hydrogels decreased with the increase in the medium pH from 3.0 to 9.0. It was also observed that HCl-treated p (APTMACl-co-AMPS)-3 hydrogels removed 39.2 +/- 0.2, and 28.1 +/- 1.0 mg/g MB and EY dyes simultaneously from their corresponding 50 ml 50 ppm aqueous mixture solutions. MB and EY adsorption by HCl-treated p (APTMACl-co-AMPS)-3 hydrogels were found to abide by pseudo-first-order adsorption kinetics. Moreover, MB adsorption by HCl-treated p (APTMACl-co-AMPS) hydrogels were found to fit with Freundlich, EY adsorption fit with Langmuir isotherms. The distribution coefficient values of HCl-treated p (APTMACl-co-AMPS) hydrogels were calculated as 3.7 +/- 0.1 and 1.3 +/- 0.1 for MB and EY, respectively. The calculated selectivity coefficient value showed that HCl-treated p (APTMACl-co-AMPS) hydrogels are at least 3-fold higher selective to MB than EY.
Poly(vinyl alcohol)-tannic Acid Cryogel Matrix as Antioxidant and Antibacterial Material
(MDPI (Multidisciplinary Digital Publishing Institute), 2022) Ari, Betül; Şahiner, Mehtap; Demirci, Şahin; Şahiner, Nurettin
The biocompatible, viscoelastic properties of poly(vinyl alcohol) (PVA) in combination with the antimicrobial and antioxidant natural polyphenolic, tannic acid (TA), and the natural flavonoid and antioxidant curcumin (Cur), were used in the preparation of PVA:TA and PVA:TA:Cur cryogel composites using cryotropic gelation to combine the individually beneficial properties. The effect of TA content on the antioxidant and antimicrobial activities of PVA:TA cryogel composites and the antioxidant activities of PVA:TA:Cur cryogel composites was determined using Trolox equivalent antioxidant capacity (TEAC) and total phenol content (TPC) assays, and were compared. The PVA:TA:Cur cryogel composite showed the highest antioxidant activity, with a TEAC value of 2.10 ± 0.24 and a TPC value of 293 ± 12.00. The antibacterial capacity of the PVA:TA and PVA:TA:Cur 1:1:0.1 cryogel composites was examined against two different species of bacteria, E. coli and S. aureus. It was found that the minimum inhibition concentration (MIC) value of the PVA:TA:Cur 1:1:0.1 cryogel composites varied between 5 and 10 mg/mL based on the type of microorganism, and the minimum bactericidal concentration (MBC) value was 20 mg/mL irrespective of the type of microorganism. Furthermore, the hemocompatibility of the PVA:TA cryogel composites was evaluated by examining their hemolytic and coagulation behaviors. PVA:TA 1:1 cryogels with a value of 95.7% revealed the highest blood clotting index value amongst all of the synthesized cryogels, signifying the potential for blood contacting applications. The release of TA and Cur from the cryogel composites was quantified at different pH conditions, i.e., 1.0, 7.4, and 9.0, and additionally in ethanol (EtOH) and an ethanol–water (EtOH:Wat) mixture. The solution released from the PVA:TA cryogels in PBS was tested for inhibition capability against α-glucosidase (E.C. 3.2.1.20). Concentration-dependent enzyme inhibition was observed, and 70 µL of 83 µg/mL PVA:TA (1:1) cryogel in PBS inhibited α-glucosidase enzyme solution of 0.03 unit/mL in 70 µL by 81.75 ± 0.96%.
Preparation of Dextran Cryogels and Some of Their Applications
(2019) Ari, Betül; Şahiner, Nurettin
In this study, dextran (DEX) cryogels were prepared using 50% divinyl sulfone (DVS)crosslinker based on the repeating unit of DEX, under cryogenic conditions viacryogellation technique. It was shown that DEX cryogels can be used as column fillersto remove toxic substances such as organic dye, methylene blue (MB), pesticide, andparaquat (PQ) which are harmful to the environment and human health. The maximumabsorption capacity of 15 mg DEX cryogels was determined as 10.69±0.14 mg/g using5 mL of 100 ppm MB dye in about seven minutes, and as 2.87±0.33 mg/g from 5 mL of40 ppm PQ pesticide in about ten minutes. The reusability of DEX cryogel for MB wasalso examined. In the consecutive use of DEX cryogel weighing ~30 mg, initiallycryogel absorbed 6.43±0.15 mg MB/g cryogel from 20 ppm 30 mL MB dye, but thisvalue decreased to 4.71±0.48 mg MB/g cryogel after the fifth use. The same cryogelreleased the same amount of MB dye after the first use of 3.78±0.33 mg MB/g cryogel,but after the fifth use the release amount decreased to 0.92±0.38 mg MB/g cryogel upontreatment with 1 M 30 mL HCl solution. The adsorption kinetics of DEX cryogel forMB were also examined and the Langmuir isotherm model with a correlation coefficientof 0.9983 and the KL value of 0.36, representing the best fit amongst the other wellknown models such as the Freundlich isotherm, Temkin, Elovich and DubininRadushkevich.
Preparation of dextran cryogels for separation processes of binary dye and pesticide mixtures from aqueous solutions
(Wiley, 2020) Ari, Betül; Yetişkin, Berkant; Okay, Oğuz; Şahiner, Nurettin
We present mechanically strong macroporous, squeezable dextran cryogels as a column filling material for the removal and separation of binary organic dye and pesticide mixtures from aquatic medium. Dextran cryogels were prepared from aqueous solutions of dextran of various molecular weights (MWs) in the presence of 20 to 50 mol% divinyl sulfone (DVS) as a cross-linker at -18 degrees C. The cryogels have interconnected irregular pores of 100 mu m in sizes, and exhibit 69-84% reversible squeezability without damaging the 3D dextran network. Their total open pore volumes (6.3-10 mL g(-1)), weight swelling ratios in water (1380%-2200%), and mechanical parameters could easily be adjusted by both DVS mol% and MW of dextran. Dextran cryogel with the highest modulus (3.8 +/- 0.5 MPa), compressive stress (8 +/- 2 MPa) and plateau stress (0.46 +/- 0.04 MPa) was obtained at 50 mol% DVS using dextran with a MW of 15 to 25 kg center dot mol(-1). Dextran cryogels are hydrolysable at pH = 1 and 9 but stable at 7.4 independent on both the degree of cross-linking and MW of dextran. At below 50 mol% DVS, they are blood compatible and possess slight thrombogenic effect with blood clotting index value of 98% +/- 5%. They are also capable to separate binary dye and pesticide mixtures from aqueous solutions via ionic interactions.
Slightly degradable, naturally antibacterial hydrogel matrixes derived from polyvinyl alcohol and linear/branched-polyethyleneimine as a wound dressing material
(Taylor & Francis Inc, 2024) Ari, Betül; Sağbaş Suner, Selin; Şahiner, Mehtap; Demirci, Şahin; Şahiner, Nurettin
PVA:PEI based film gels were prepared at various weight ratios, 10-100% of linear-PEI (L-PEI) and branched-PEI (B-PEI) to PVA as PVA:L-PEI or PVA:B-PEI to demonstrate the effect of PEI types on hydrolytic degradation, blood compatibility, antibacterial properties, and cytotoxicity. The hydrolytic degradation studies, done at similar to skin pH, 5.4 and revealed that PVA:PEI-based film gels, 1:0.1 wt% are degradable with a gravimetric weight losses of16.80 +/- 1.39% and 17.20 +/- 1.21% up to 7 days, and decreased as the wt% of L-PEI and B-PEI were increased in the matrix. The blood compatibility assays done through hemolysis and blood clotting tests disclosed only PVA:B-PEI film gels at 1.0 mg/mL concentration were found blood compatible. The antimicrobial studies revealed that regardless of the types and weight ratio of L-PEI or B-PEI, all PVA:L-PEI and PVA:B-PEI based film gels possess a potent antibacterial activity against Pseudomonas aeruginosa, a gram-negative bacteria and Staphylococcus aureus, a gram-positive bacteria. Moreover, the cytotoxicity test results examined on the L929 cell line uncovered that only PVA:L-PEI and PVA:B-PEI even at very low concentrations of L-PEI or B-PEI, for example, PVA:L-PEI and PVA:B-PEI at 1:0.1 weight ratio film gel at 10 mg/mL show toxic effect, for example <50% cell viability suggesting lesser concentration use in biomedical applications.
Super-Macroporous Pulluan Cryogels as Controlled Active Delivery Systems with Controlled Degradability
(Mdpi, 2023) Ari, Betül; Şahiner, Mehtap; Sağbaş Suner, Selin; Demirci, Şahin; Şahiner, Nurettin
Here, super-macroporous cryogel from a natural polysaccharide, pullulan was synthesized using a cryo-crosslinking technique with divinyl sulfone (DVS) as a crosslinker. The hydrolytic degradation of the pullulan cryogel in various simulated body fluids (pH 1.0, 7.4, and 9.0 buffer solutions) was evaluated. It was observed that the pullulan cryogel degradation was much faster in the pH 9 buffer solution than the pH 1.0 and 7.4 buffer solutions in the same time period. The weight loss of the pullulan cryogel at pH 9.0 within 28 days was determined as 31% & PLUSMN; 2%. To demonstrate the controllable drug delivery potential of pullulan cryogels via degradation, an antibiotic, ciprofloxacin, was loaded into pullulan cryogels (pullulan-cipro), and the loading amount of drug was calculated as 105.40 & PLUSMN; 2.6 & mu;g/mg. The release of ciprofloxacin from the pullulan-cipro cryogel was investigated in vitro at 37.5 & DEG;C in physiological conditions (pH 7.4). The amount of drug released within 24 h was determined as 39.26 & PLUSMN; 3.78 & mu;g/mg, which is equal to 41.38% & PLUSMN; 3.58% of the loaded drug. Only 0.1 mg of pullulan-cipro cryogel was found to inhibit half of the growing Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) colonies for 10 min and totally eradicated within 2 h by the release of the loaded antibiotic. No significant toxicity was determined on L929 fibroblast cells for 0.1 mg drug-loaded pullulan cryogel. In contrast, even 1 mg of drug-loaded pullulan cryogel revealed slight toxicity (e.g., 66% & PLUSMN; 9% cell viability) because of the high concentration of released drug.
Superporous poly(β-Cyclodextrin) cryogels as promising materials for simultaneous delivery of both hydrophilic and hydrophobic drugs
(Pergamon-Elsevier Science Ltd, 2022) Ari, Betül; Demirci, Şahin; Ayyala, Ramesh S.; Salih, Bekir; Şahiner, Nurettin
Here, one step, simple preparation of superporous p(beta-cyclodextrin) (p(beta-CD)) cryogels in the presence of various ratios of crosslinker, divinyl sulfone (DVS) e.g., 100, 150, 200% mole with respect to the mole ratio of 6 hydroxyl groups on beta-CD unit under cryogenic conditions were reported for the first time. The swelling properties, and hydrolytic degradation of p(beta-CD) cryogels was directly related to the used crosslinker ratio. It was observed that the p(beta-CD) cryogels showed higher swelling% in DMSO and DMF than in DI water. The prepared p(beta-CD)-1 cryogel that was 100% crosslinked exhibited 14 +/- 3.7%, 34 +/- 4.8%, and 45 +/- 6.2% weight losses within 20 days in pH 5.4, 7.4, and 9.0 buffer solutions, respectively. An acceptable hemolysis index of < 5% and a blood coagulation index, >89% were observed for the p(beta-CD) cryogels at 1 mg/mL concentrations. Additionally, the potential useability of p(beta-CD) cryogels as in vitro drug delivery systems for both hydrophilic vancomycin, and hydrophobic tetracycline as model drugs were individually illustrated at pH 7.4 in PBS. The cumulative drug release from p(beta-CD) cryogels, in sustained release profiles with 76.7 +/- 9.0 mg/g of vancomycin (89.9 +/- 10.5% of the loaded amount) and 146.5 +/- 19.4 mg/g tetracycline g (83.1 +/- 6.3% of the loaded amount) were attained in 6 and 54 h, respectively at pH 7.4 in PBS. Most importantly, p(beta-CD) cryogels exhibited simultaneous loading and releasing the ability for both hydrophilic vancomycin, and hydrophobic tetracycline drugs by concurrently releasing 37.0 +/- 2.7 mg/g (23.4 +/- 1.8% of the loaded amount), and 36.3 +/- 1.3 mg/g (23.6 +/- 0.8% of the loaded amount), respectively at pH 7.4 (PBS) in 10 h.
Surface-modified carbon black derived from used car tires as alternative, reusable, and regenerable catalysts for H2 release studies from sodium borohydride methanolysis
(Wiley, 2019) Ari, Betül; Ay, Mehmet; Sunol, Aydin K.; Şahiner, Nurettin
Carbon black (CB) obtained from used car tire rubbers were treated with concentrated sulfuric and nitric acids. The oxidized CB (CB-COO-Na+) is subsequently modified with epichlorohydrin (ECH) and amines including polyethylene imine (PEI). These modified CBs such as CB-PEI are used as metal-free catalysts in methanolysis of sodium borohydride (NaBH4) to produce hydrogen. The hydrogen generation rate (HGR) of 3089 +/- 44.69 mL.min(-1).g(-1) is accomplished at room temperature with CB-PEI-hydrochloric acid (HCl) catalyst. The resulting activation energy of 34.7 kJ/mol for the temperature range of -20 degrees C to +30 degrees C compares favorably to most of alternative catalysts reported in literature while reaction catalyzing capabilities of CB-PEI-HCl particles extend to the subzero temperature range (-20 degrees C-0 degrees C). The reuse and regeneration studies conducted for the CB-PEI-HCl catalyst showed that these catalysts do provide complete conversion at every use up to five consecutive runs and retain 50 +/- 2.5% of the original hydrogen generation rate at the fifth consecutive reuse. The CBs-based catalysts are fully regenerated with HCl treatment.
Tunable Biopolymeric Drug Carrier Nanovehicles and Their Safety
(Springer Singapore, 2020) Sağbaş Suner, Selin; Ari, Betül; Demirci, Şahin; Şahiner, Nurettin
Biopolymers are types of biomolecules encompassing a wide range of macromolecules such as polysaccharides, proteins, DNA, RNA, enzymes, and polyphenols that are abundant in nature. The most striking properties of these biopolymers are that they are renewable, eco-friendly, nontoxic, biodegradable, and natural, and most of the time, they are relatively inexpensive materials. The capability to design novel material through nanotechnology and related developments have widened and enabled the development of superior-controlled drug delivery systems. Because of the unique properties of biopolymers together with nanotechnology capabilities, the use of biopolymeric nanomaterials as a drug nanocarrier was inevitable. This chapter covers the literature in the field of biopolymeric nanovehicle design for tailor-made devices such as drug carriers. The advantages and disadvantages of loading techniques such as physical, chemical, and encapsulation methods in the preparation of biopolymeric drug carrier vehicles are discussed. Finally, the potential application area of these biopolymeric carriers from ocular delivery to targeted cancer therapy and, especially, their safety will be outlined with clinical evidence. © Springer Nature Singapore Pte Ltd. 2021.

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