Stress field analysis around optical fiber embedded in composite laminae under transverse loading

U ovome radu analiziran je uticaj ugrađenog optičkog vlakna na naponsko stanje transferzalno opterećene kompozitne lamine. Ugrađeno optičko vlakno ima primetan uticaj na naponsko polje kompozitne lamine. Vrednosti komponentnih napona u lamini sa ugrađenim optičkim vlaknom imaju i do 40% veće vrednosti od nominalnih. Za razmatrani slučaj opterećenja optičko vlakno ugrađeno u kompozitnu laminu jeste generator primetnih ali ne i značajnih koncentracija napona u poređenju sa onima koje, na primer, mogu da se jave usled geometrije oblika.The influence of embedded optical fiber on stress state of transversally loaded composite laminae was analyzed in this paper. The optical fiber interaction with the host material (composite) has noticeable effect on the stress field of laminae. For considered load case, values of the component stresses in laminae with embedded optical fiber have values up to 40% higher than the nominal ones. For the observed loading scenario, optical fibers are acting as generators of evident but not significant stress, comparing to the stress concentrations that could arise, for instance, as a consequence of the shape geometry

Modeling of the matrix porosity influence on the elastic properties of particulate biocomposites

Porozni materijali se koriste za široki spektar inženjerskih struktura napravljenih na bazi keramike, poroznih legura sa memorijskim efektom, penastih struktura, termički zaštitnih filmova. U skorije vreme primena poroznih biokompozita u inženjerstvu tvrdih tkiva kao i implanata kod koštanih defekata privlači posebnu pažnju. Uticaj matrične poroznosti na karakteristike elastičnosti čestičnih biokompozita analiziran je primenom metode konačnih elemenata upotrebom dvofaznog i trofaznog modela napravljenog na bazi reprezentativnog zapreminskog elementa - RZE. Razvijen je trofazni model RZE sa čestičnim ojačanjem raspoređenim u površinski centrirano kubnom rasporedu sa matričnom poroznošću oblika sfere, čiji su rezultati upoređeni sa jednostavnim analitičkom modelima. Primećeno je da matrična poroznost značajno utiče na karakteristike elastičnosti ovih vrsta kompozita. Rezultati dobijeni na osnovu dvofaznog modela imaju više vrednosti od onih dobijenih na osnovu trofaznog modela u skoro celom analiziranom opsegu usled fizičke granice za zapreminski udeo poroziteta kod trofaznog modela koja je očigledno određena vrednošću zapreminskog udela čestice ojačanja.For a wide range of engineering structures such as ceramics, porous shape memory alloys, foam-like structures and thermal spray deposits, porous materials have been used. Recently, porous biocomposites for the applications to bone implants and hard tissue engineering have become increasingly important. The effect of matrix porosity on the elastic properties of particulate biocomposite was studied by two-and three-phase unit cell finite element models. A 3D FCC unit cell model of particulate composite with included matrix porosity is developed and compared with the simple theoretical models. It is found that the matrix porosity has noticeable influence on the composite elastic properties. The two-phase predictions overestimate the three-phase ones because of the physical threshold for three-phase model determined by the particle content

In vitro and in vivo performance of nanosized hydroxyapatite particles coated with poly-dl-lactide-co-glycolide as systems for drug delivery of tigecycline

Calcium-phosphate/poly(dl-lactide-co-glycolide) (CP/PLGA) composite biomaterial in granular form showed a high potential in the reconstruction of bone tissue. Compared to pure polymers, the combination of CP with biodegradable polymers used in bone drug delivery systems shows certain advantages. Composite biomaterials in nano particulate (NPs) form may have significant advantages over those in micro- or submicro-particulate form. The purpose of the study presented in this paper has been to examine the possibility of the synthesis of a new nanoparticulate system for controlled and systemic drug delivery with double effect. In the first step, a drug is released from bioresorbable polymer; in the second stage, after resorption of the polymer, non-bioresorbable calcium phosphate remains the chief part of the particle and takes the role of a filler, filling a bone defect. The obtained tigecycline-loaded calcium-phosphate(CP)/poly(dl-lactide-co-glycolide)(PLGA) nano particles contain calcium phosphate coated with bioresorbable polymer and 0.6, 2 and 5wt% tigecycline. The composite was analyzed by FT-IR, XRD, HPLC and AFM methods. The average particle size of the nanocomposite increases with the augmentation of the part of antibiotics, and it ranges from 65 to 95 nm. Release profiles of tigecycline were obtained by UV-VIS spectroscopy in physiological solution at 37oC. Experimental results were analyzed using Peppas and Weibull mathematical models. Based on kinetic parameters, tigecycline release was defined as non-Fickian transport. The in vitro cytotoxicity of the nanocomposite was examined on standard cell lines of MC3T3-E1, in vitro. The obtained low values of LDH activity (under 37%) indicate low cytotoxicity level. Inhibition of bacteria in aerobic and anaerobic conditions in vitro was analyzed after 1, 2 and 3 weeks. The behaviour of the composite under real-life conditions was analyzed through implantation of the nanocomposite into living organisms, in vivo. The system with the lowest tigecycline content proved to be an adequate system for local and controlled release

Modeling of the matrix porosity influence on the elastic properties of particulate biocomposites

Porozni materijali se koriste za široki spektar inženjerskih struktura napravljenih na bazi keramike, poroznih legura sa memorijskim efektom, penastih struktura, termički zaštitnih filmova. U skorije vreme primena poroznih biokompozita u inženjerstvu tvrdih tkiva kao i implanata kod koštanih defekata privlači posebnu pažnju. Uticaj matrične poroznosti na karakteristike elastičnosti čestičnih biokompozita analiziran je primenom metode konačnih elemenata upotrebom dvofaznog i trofaznog modela napravljenog na bazi reprezentativnog zapreminskog elementa - RZE. Razvijen je trofazni model RZE sa čestičnim ojačanjem raspoređenim u površinski centrirano kubnom rasporedu sa matričnom poroznošću oblika sfere, čiji su rezultati upoređeni sa jednostavnim analitičkom modelima. Primećeno je da matrična poroznost značajno utiče na karakteristike elastičnosti ovih vrsta kompozita. Rezultati dobijeni na osnovu dvofaznog modela imaju više vrednosti od onih dobijenih na osnovu trofaznog modela u skoro celom analiziranom opsegu usled fizičke granice za zapreminski udeo poroziteta kod trofaznog modela koja je očigledno određena vrednošću zapreminskog udela čestice ojačanja.For a wide range of engineering structures such as ceramics, porous shape memory alloys, foam-like structures and thermal spray deposits, porous materials have been used. Recently, porous biocomposites for the applications to bone implants and hard tissue engineering have become increasingly important. The effect of matrix porosity on the elastic properties of particulate biocomposite was studied by two-and three-phase unit cell finite element models. A 3D FCC unit cell model of particulate composite with included matrix porosity is developed and compared with the simple theoretical models. It is found that the matrix porosity has noticeable influence on the composite elastic properties. The two-phase predictions overestimate the three-phase ones because of the physical threshold for three-phase model determined by the particle content

3D štampa i karakterizacija nosača za dostavu ibuprofena u koštanom tkivu

In this work, a blend of gelatin A (GA) and polyvinylpyrrolidone (PVP K30) was used for semi-solid 3D printing of bone scaffold for ibuprofen (IBU) delivery. The cross-linking of the obtained scaffold was performed with a 1% glutaraldehyde (GTA) solution, followed by lyophilization. The thermal and mechanical properties, as well as drug release profiles, and drug kinetics of prepared scaffolds were investigated. The cross-linked and lyophilized scaffold has shown good thermal stability, mechanical properties, and prolonged release of IBU following the Fickian diffusion process.Nosač za dostavu ibuprofena (IBU) u koštanom tkivu dobijen je metodom 3D štampe ekstruzijom iz paste uz korišćenje smeše polimera želatina A (GA) i polivinilpirolidona (PVP K30). Dobijeni nosač je umrežen sa 1% rastvorom glutaraldehida (GTA), nakon čega je usledio proces liofilizacije uzoraka. Ispitivana su mehanička i termička svojstva, profili i kinetika oslobađanja ibuprofena iz dobijenih nosača. Umrežen i liofilizovan nosač pokazao je dobru termičku stabilnost i mehanička svojstva, kao i produženo oslobađanje IBU-a koje prati kinetiku po Fikovom zakonu difuzije

Freeze-drying method to produce a range of PCL particles with tailored morphological properties

Poly (ε-caprolactone) (PCL) is a widely investigated bioresorbable polymer and it has been extensively used in numerous biomaterials applications especially in tissue engineering and drug delivery systems. Freeze-dried particles of poly (ε-caprolactone), with different morphological characteristics (spherical or cube in shape), were prepared by physicochemical method with solvent/non-solvent systems and by using the different types of cryoprotectants. Natural polymer poly (L-glutamic acid) (PGA) as well as disaccharide, saccharose, were used as cryoprotectant i.e. substance that is used to protect particles from freezing damage (damage due to ice formation). PGA has dual role in the synthesis; besides as cryoprotectant, it acts as stabilizer of the particles i.e. to prevent their agglomeration. The samples were characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The biocompatibility of the samples was examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The formation of intracellular reactive oxygen species was measured spectrophotometrically using a fluorescent probe

In vitro evaluation of a multifunctional nano drug delivery system based on tigecycline-loaded calcium-phosphate/ poly-DL-lactide-co-glycolide

Most drug delivery systems as treatment modalities for osteomyelitis have not been evaluated for resistant infections. Tigecycline (TG) is an antimicrobial agent that could be used in the treatment of multi-drug-resistant orthopedic infections. The objective of this in vitro study has been to determine what dosage of TG causes changes in the morphology and number of osteoblasts. We have also investigated whether nanoparticulate tigecycline-loaded calcium-phosphate/poly-DL-lactide-co-glycolide is biocompatible and whether it could release bioactive TG in a controlled manner during the observation time. The cytotoxicity was tested by analyzing the release of lactate dehydrogenase from dead osteoblasts to the medium. Staphylococcus aureus was used to verify the antibacterial effect of the multifunctional drug delivery system. At concentrations as achieved by local application, TG caused high toxic effect and impaired the normal osteoblastic morphology. The nanoparticulate multifunctional drug delivery system showed good compatibility and antibacterial effect during the observation time and thus appears to be suitable for the treatment of osteomyelitis caused by multi-drug-resistant microbes.This is accepted peer-reviewed version of the article: Ignjatović, N. L., Ninkov, P., Sabetrasekh, R., Lyngstadaas, S. P., & Uskoković, D. P. (2014). In vitro evaluation of a multifunctional nano drug delivery system based on tigecycline-loaded calcium-phosphate/poly-DL-lactide-co-glycolide. Bio-medical materials and engineering, 24(4), 1647-1658. [https://dx.doi.org/10.3233/BME-140978]Published version: [https://vinar.vin.bg.ac.rs/handle/123456789/7504

Functionalization of graphene nanoplatelets via Bingel reaction for polymer nanocomposites

In this study, we have performed functionalization of graphene nanoplatelets (GNPs) via Bingel reaction and investigated influence on the addition of covalently functionalized GPNs on the structural changes of the poly(methyl methacrylate). Preparation of poly(methyl methacrylate) nanocomposites with functionalized GNPs has been accomplished by drop casting method of dissolved PMMA mixed with modified graphene nanoplatelets dispersed in a N-methyl-1-pyrrolidone. Functionalizaton of graphene has been achieved under the conditions of Bingel reaction, which implies introduction of diethyl malonate on the graphene surfaces through the cyclopropane ring formation. Introduction of the cyclopropane ring on to the surface of graphene does not significantly affect the initial structural properties of graphene nanoplatelets, allowing better dispersible properties due to interaction of covalently attached diethyl malonate groups with the polymer chains. Fourier transform infrared spectroscopy (FTIR) and elemental analysis confirmed the effectiveness of the addition of diethyl malonate via Bingel reaction on the surface of GNPs. Scanning electron microscopy (SEM) has been used to provide information on the morphology of functionalized GNPs. Prepared nanocomposites have been characterized by Raman and FTIR spectroscopy. The changes regarding glass transition temperature have been monitored with differential scanning calorimetry (DSC)

Analiza formiranja PVB-SiO2 nanokompozitnih vlakana pomoću elektrospining procesa

The poly (vinyl butyral)-silica (PVB-SiO2) nanofibers were obtained by the electrospinning process. The experiments were carried out with PVB solution in concentration of 10 wt.% where ethanol was used as the solvent. The silica nanoparticles were added in the solution in different contents of 1, 3 and 5 wt.% SiO2 and nanoparticles were modified with γ-aminopropyltriethoxysilane (AMEO silane). The impacts of the parameters of the electrospinning process and the silica nanoparticles on the produced PVB-SiO2 nanocomposite fibers were tested. The structures of the PVB-SiO2 nanocomposite fibers were investigated using optical microscopy and scanning electron microscopy (SEM). The morphology and distribution of the resulting nanofibers were analyzed using the software Image-Pro Plus. .Poli (vinil butiral)-silika (PVB-SiO2) nanovlakna su dobijena metodom elektrospininga. Eksperimenti su izvedeni u rastvoru 10 mas.% PVB-a u etanolu koji je korišćen kao rastvarač. Nanočestice silike su dodate sa različitim sadržajem od 1, 3 i 5 mas.% SiO2 i modifikovane γ-aminopropiltrietoksi silanom (AMEO silanom). Istražen je uticaj procesnih parametara elektrospininga na nanokompozitna vlakna PVB-SiO2. Struktura PVB-SiO2 nanokompozitnih vlakana je proučavana pomoću optičke mikroskopije i skenirajuće elektronske mikroskopije (SEM). Morfologija proizvedenih nanokompozitnih vlakana i njihova raspodela je analizirana u Image Pro Plus softveru.

Effects of different cryoprotectants on morphology of lyophilized poly(ε-caprolactone) micro and nanospheres

A common limitation of using polymeric micro and nanoparticles in long-term conservation is due to their poor physical and chemical stability. Freeze-drying is one of the most convenient methods that enable further reconstitution of micro and nanoparticles for therapeutical use. Nevertheless, this process generates various stresses during freezing and desiccation steps. The aim of this study was to evaluate different cryoprotectants (protective excipients that are usually added to increase stability upon storage and protect the particles from freezing stress): sugars (glucose and sucrose) and polymers (PVA and PGA), on the outcome of freeze-dried poly(ε-caprolactone) micro and nanospheres. The best freeze-drying results in terms of morphological characteristics, analyzed with SEM, were achieved with glucose at concentration of 1%. The FTIR analysis confirmed that the molecular structure of PCL particles remained the same after the addition cryoprotectants