B4C /Al KOMPOZİTLERİN TAKVİYE HACİM ORANINA BAĞLI OLARAK ABRASİF AŞINMA DAVRANIŞLARININ İNCELENMESİ

Bu çalışmada, toz metalurjisi yöntemi ile üretilen Al matrisli B4C parçacık takviyeli kompozitlerin kuru kayma koşullarındaki aşınma davranışları incelenmiştir. Kompozitlerin karekterizasyonu mikroyapı incelemeleri, sertlik ölçümleri ve abrasif aşınma deneyleri ile yapılmıştır. Abrasif aşınma testleri, 180 ve 400 Mesh Al2O3 zımpara kullanılarak 10 N ve 20 N yük altında 0,2 m s-1 kayma hızında gerçekleştirilmiştir. Sertlik B4C parçacık ilavesi ile birlikte artmıştır. % 20 B4C parçacık takviyeli kompozit en yüksek sertlik gösterirken, % 10 B4C parçacık takviyeli kompozit en yüksek aşınma direnci göstermiştir

Development of PEI-RANK siRNA Complex Loaded PLGA Nanocapsules for the Treatment of Osteoporosis

Osteoporosis, which is characterized by low bone mineral density and susceptibility to fracture, is caused by increased osteoclastic activity. Receptor activator of nuclear factor kappa B ligand (RANKL)/RANK signaling plays an important role in osteoclast differentiation and activation. The current treatment strategies for osteoporosis do not directly address this underlying cause and generates undesired side effects. This led to emergence of controlled delivery systems to increase drug bioavailability and efficacy specifically at the bone tissue. With better understanding of molecular pathology of bone, the use of small interfering RNA (siRNA) to inhibit translation of abnormal gene expression in cells is becoming a promising approach. In this study, we report a siRNA delivery system consisting of PEI:RANK siRNA complex entrapped in nanosized poly(lactic acid-co-glycolic acid) (PLGA) capsules intended to be used in the treatment of osteoporosis. The nanosize will enable the nanoparticles to be administered by intravenous injection. The RANK siRNA was complexed with polyethylenimine (PEI) and loaded into biodegradable PLGA nanocapsules (NCs). The PEI:RANK siRNA loaded nanocapsules significantly reduced (47%) RANK mRNA levels. The differentiation of osteoclast precursors to mature osteoclasts was significantly suppressed (approximate to 54%). The reduction in the osteoclastic activity of the differentiated osteoclasts (55%) was found to be statistically significant. The siRNA delivery system developed in the study is planned to be tested i.v. in mouse and has the potential to be used as a novel alternative approach for the systemic treatment of osteoporosis

Construction of a PLGA based, targeted siRNA delivery system for treatment of osteoporosis

Osteoporosis, a systemic skeletal disorder, occurs when bone turnover balance is disrupted. With the identification of the genes involved in the pathogenesis of the disease, studies on development of new treatments has intensified. Shortinterfering RNA (siRNA)is used to knockdown disease related gene expressions. Targeting siRNA in vivo is challenging. The maintenance of therapeutic plasma level is hampered by clearance of siRNA from the body. Targeted systems are useful in increasing the drug concentration at the target site and decreasing side effects. Aim of the present study was to develop an injectable siRNA delivery system toprotect siRNA during systemic distribution and target the siRNA to bone tissue using a thermoresponsive, genetically engineered, elastin-like recombinamer (ELR), designed to interact withthe mineral component of bone. The delivery system consisted of DNAoligo as a siRNA substitute complexed with the cationic polymer, polyethyleneimine (PEI), at N/P ratio of 20. The complex was encapsulated in poly(lactic acid-co-glycolic acid) (PLGA) nanocapsules. PLGA capsules were characterized bySEM, TEM and XPS. FTIR was used to show the preferential attachment of ELR to HAp. Encapsulation efficiency of the complex in PLGA nanocapsules was 48%. The release kinetics of the complex fits the Higuchi release kinetics

Yapay kıkırdak oluşturulmasında üç boyutlu biyopolimerik yapıların kullanılması

TÜBİTAK MİSAG01.03.2002Sınırlı iyileşme yetisi olan eklem kıkırdağının yaralanmalarında doku mühendisliği ürünü olan yapay ğların kullanılması güncel araştırma konularındandır. Bu çalışmayla kondrositlerin üzerinde üreyerek yaşayabileceği kalsiyum fosfat içeren kollagen ve Poli (3-hidroksibütirat-ko-3-hidroksivalerat) (PHBV8, %8 HV içeren PHBV)den süngersi ağlar üretilmiş ve karakterizasyonları gerçekleştirilmiştir. 20 hafta takip edilen polimer kompozitlerin çok az yabancı cisim yanıtı oluşturduğu ve kıkırdak iyileşmesini sağlayabildikleri gözlenmiştir. Üretilen polimer ağların gelecekte insanların kıkırdak yaralanmalarında kullanılabileceği kanaatine varılmıştır

How safe is the use of prosthetic materials in the repair of abdominal-wall defects in malnourished subjects?

Incisional hernias and abdominal-wall defects consume large amounts of healthcare resources. Use of mesh is effective in treatment of these disorders and can decrease the rate of recurrence. This experimental study focused on the safety of mesh use in the setting of malnutrition, a condition that impairs wound healing. Rats were divided into two groups: normally fed and food-restricted. An abdominal-wall defect, 2 by 2 cm, was covered with polypropylene mesh, 2.5 by 2.5 cm. After sacrifice of the rats at the 21st and 60th days, tissue samples were sent for tensiometric and histopathological studies. No significant difference in infectious complications was observed between the two groups. Tensiometry revealed no significant differences between the groups. On histopathological examination, the only difference noted was in the vascularization scores of normally fed rats. For malnourished subjects that survived after surgery, the use of polypropylene mesh appeared safe in the closure of abdominal-wall defects, with no increase in infection rate and satisfactory wound healing