Browsing by Author "Keskin, Dilek"

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Composite clinoptilolite/PCL-PEG-PCL scaffolds for bone regeneration: In vitro and in vivo evaluation
(2019) Pazarceviren, Ahmet Engin; Dikmen, Tayfun; Altunbas, Korhan; Yaprakci, Volkan; Erdemli, Ozge; Keskin, Dilek; Tezcaner, Aysen; 0000-0001-8606-8863; 31475790; AAG-3927-2019
In this study, clinoptilolite (CLN) was employed as a reinforcement in a polymer-based composite scaffold in bone tissue engineering and evaluated in vivo for the first time. Highly porous, mechanically stable, and osteogenic CLN/PCL-PEG-PCL (CLN/PCEC) scaffolds were fabricated with modified particulate leaching/compression molding technique with varying CLN contents. We hypothesized that CLN reinforcement in a composite scaffold will improve bone regeneration and promote repair. Therefore, the scaffolds were analyzed for compressive strength, biodegradation, biocompatibility, and induction of osteogenic differentiation in vitro. CLN inclusion in PC-10 (10% w/w) and PC-20 (20% w/w) scaffolds revealed 54.7% and 53.4% porosity, higher dry (0.62 and 0.76 MPa), and wet (0.37 and 0.45 MPa) compressive strength, greater cellular adhesion, alkaline phosphatase activity (2.20 and 2.82 mg/g(DNA)/min), and intracellular calcium concentration (122.44 and 243.24 g Ca/mg(DNA)). The scaffolds were evaluated in a unicortical bone defect at anterior aspect of proximal tibia of adult rabbits 4 and 8 weeks postimplantation. Similar to in vitro results, CLN-containing scaffolds led to efficient regeneration of bone in a dose-dependent manner. PC-20 demonstrated highest quality of bone union, cortex development, and bone-scaffold interaction at the defect site. Therefore, higher CLN content in PC-20 permitted robust remodeling whereas pure PCEC (PC-0) scaffolds displayed fibrous tissue formation. Consequently, CLN was proven to be a potent reinforcement in terms of promoting mechanical, physical, and biological properties of polymer-based scaffolds in a more economical, easy-to-handle, and reproducible approach.
The relationship of serum vitamin D receptor levels with disease activity and clinical parameters in patients with ankylosing spondylitis
(2019) Kultur, Turgut; Oztas, Dilek; Keskin, Dilek; Keskin, Goksal; Inal, Ali; Kara, Halil; 31893276
Objectives: The aim of this study was to investigate the relationship between serum vitamin D receptor (SVDR) levels and disease activity parameters in patients with ankylosing spondylitis (AS). Patients and methods: Between July 2016 and January 2017, a total of 62 patients (51 males, 11 females; mean age 36.5 +/- 12.8 years; range, 23 to 49 years) with AS and 32 healthy volunteers (25 males, 7 females; mean age 41.57 +/- 13.6 years; range, 26 to 48 years) were included in the study. The SVDR levels were measured using the enzyme-linked immunosorbent assay. Erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) levels were recorded. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores were used to assess disease activity. Results: Although there was no significant difference between the patient and control groups (p=0.66), SVDR levels were significantly elevated in patients with active AS (BASDAI score >= 4) (p=0.01). The SVDR levels significantly increased in AS patients with peripheral joint involvement and enthesitis (p=0.01, p=0.05, respectively). The SVDR levels significantly elevated in patients treated with non-steroidal anti-inflammatory drugs, compared to those treated with biological agents and control group (p=0.01, p=0.03, respectively). The SVDR levels were positively correlated with the BASDAI, CRP and ESR in the patient group (p=0.01, r=0.751; p=0.01, r=0.75; p=0.01, r=0.81, respectively). Conclusion: Our study results suggest that serum SVDR levels are associated with the disease activity and clinical parameters in patients with AS. Based on these findings, SVDR level may be used as a marker of disease activity in AS.
Xanthan-Gelatin And Xanthan-Gelatin-Keratin Wound Dressings For Local Delivery Of Vitamin C
(2022) Demir, Gizem Cigdem; Erdemli, Ozge; Keskin, Dilek; Tezcaner, Aysen; https://orcid.org/0000-0001-8606-8863; 000780824900002; AAF-4496-2019
Recently, functional dressings that can protect the wound area from dehydration and bacterial infection and support healing have gained importance in place of passive dressings. This study aimed to develop temporary and regenerative xanthan/gelatin (XGH) and keratin/xanthan/gelatin hydrogels (KXGHs) that have high absorption capacity and applicability as a wound dressing that can provide local delivery of Vitamin C (VC). Firstly, xanthan/gelatin hydrogels were produced by crosslinking with different glycerol concentrations and characterized to determine the hydrogel composition. According to their weight ratios, xanthan, gelatin, and glycerol hydrogels are named. If their weight ratio is 1:1:2 (w/w/w), the group name is selected as X1:GEL1:GLY2. X1: GEL1:GLY2 hydrogel was selected for biocompatibility, mechanical property, water vapor transmission rate (WVTR), and porosity. The addition of keratin to X1:GEL1:GLY2 improved L929 fibroblasts viability and increased protein release. Water vapor transmission of XGHs and KXGHs was between 3059.09 & PLUSMN; 126 and 4523 & PLUSMN; 133 g m(-2) d(-1); therefore, they can be suitable for granulating, low to moderate exudate wounds. XGH and KXGHs loaded with VC had higher water uptake, making it more convenient for exudate wounds. VC was released for 100 h, and VC containing XGHs and KXGHs increased the collagen synthesis of L929 fibroblasts. All of the hydrogels (XGH, KXGH, and VC-KXGHs) inhibited the bacteria transmission. In conclusion, our results suggest that VC-XGH and VC-KXGH can be candidates for temporary wound dressing materials for skin wounds.