Bir Facile ve çevre dostu Rota Kademeli Gözenek Boyutu Poli (Laktik Asit) iskeleleri imal etmek için

Summary

In this work, poly(lactic acid)/polyethylene glycol (PLA/PEG) scaffolds were prepared by using a combination of melt mixing and selective leaching. The method herein discussed permitted to develop three-layer scaffolds by highly controlling both porosity and pore size. The mechanical properties were also evaluated in a physiological environment.

Abstract

Over the recent years, functionally graded scaffolds (FGS) gaineda crucial role for manufacturing of devices for tissue engineering. The importance of this new field of biomaterials research is due to the necessity to develop implants capable of mimicking the complex functionality of the various tissues, including a continuous change from one structure or composition to another. In this latter context, one topic of main interest concerns the design of appropriate scaffolds for bone-cartilage interface tissue. In this study, three-layered scaffolds with graded pore size were achieved by melt mixing poly(lactic acid) (PLA), sodium chloride (NaCl) and polyethylene glycol (PEG). Pore size distributions were controlled by NaCl granulometry and PEG solvation. Scaffolds were characterized from a morphological and mechanical point of view. A correlation between the preparation method, the pore architecture and compressive mechanical behavior was found. The interface adhesion strength was quantitatively evaluated by using a custom-designed interfacial strength test. Furthermore, in order to imitate the human physiology, mechanical tests were also performed in phosphate buffered saline (PBS) solution at 37 °C. The method herein presented provides a high control of porosity, pore size distribution and mechanical performance, thus offering the possibility to fabricate three-layered scaffolds with tailored properties by following a simple and eco-friendly route.

Introduction

The interest in biodegradable polymers has grown in importance during the last years both in academia and in the industry, due to the rising concerns regarding plastic waste and the reduction in using non-renewable sources^1-7. In particular, biocompatible and biodegradable synthetic polymers are widespread in several biomedical application fields, such as drug controlled release^8,9, absorbable suture threads^8,10, bioprocess intensification¹¹ and tissue engineering¹².

Tissue engineering focuses on the development of devices capable to restore and maintain normal function in diseased or injured tissues. Most of the native tissues are composed by different types of cells and extracellular matrices (ECMs) in specific spatial hierarchies. For example, articular cartilage (AC) consists of different zones with varying types and orientations of collagen fibers and collagen-binding proteins. Moreover, cartilage and bone show significantly different hierarchical structures. In this context, the preparation of multilayer scaffolds with engineered properties in each layer could allow replacing heterogeneous tissues by taking into accounts all the local microenvironments of these complex systems^13,14.

Based on the cellular/biological and/or physical-chemical characteristics of the scaffolds, the main strategies adopted by the tissue engineering can be divided into monophasic, biphasic, and triphasic. Biphasic and triphasic approaches (BTA) use two or three different pores architectures, materials, or fillers to prepare multilayered functional devices. Furthermore, a single material can be used to achieve biphasic or triphasic devices, as long as it is possible to create a gradient in its physical properties¹².

Cell migration plays a key-role in the morphogenesis, inflammation, wound healing and tumor metastasis. Cell movement is encouraged by the presence of a gradient of chemical-physical properties from the surface to the core of the device. Therefore, biomaterials fulfilling the above discussed requirements can be helpful in studying cell migration. In addition to chemical gradients that trigger cells migration (chemotaxis), mechanical properties of cells culture substrate can also lead to cell movement (mechanotaxis)¹⁵.

The multilayer structure can also provide the tunable release of specific drugs incorporated within the polymer matrix, by changing the specific area of the layer or the amount of loaded drugs.

Over the past decade, in order to develop scaffolds possessing a discrete or continuous gradient of morphological properties, such as porosity or pore size, several approaches have been presented^16-31. The most recent papers focused on the preparation of BTA by adopting: particle leaching ^12,28,32, gas foaming technique¹⁶, electrospinning^17-19, layer by layer casting technique²⁰, rapid prototyping^21,22, thermally induced phase separation (TIPS)²², centrifugation freeze drying^24,25, triply periodic minimal surfaces (TPMS)²⁶, freeze casting^27-30.

Within the frame of this work, we present a fast and simple route to achieve PLA-based three-layer porous scaffolds (TLS), by combining melt mixing, compression molding and salt leaching. Differently from most of the technologies commonly used for scaffold production, the strategy herein adopted can be considered fully eco-friendly, since it does not require any toxic solvent potentially dangerous for environment and for living cells and tissues³². The basic processing-structure-property relationships established in this study by analyzing both morphological features and mechanical behavior of fabricated devices provide guidance to future advances in designing multifunctional graded scaffolds with specific target properties.

Protocol

1. İskele İmalatı 20 dakika boyunca, bir laboratuar blenderi içinde NaCI eziyet ve 100 ° C'de bir ısıtıcı üzerinde kurutun. rezonans meydana gelmeden yüksek frekansa 30 dakika için bir eleme makinesinde kurutuldu NaCl (zamanda 45 g) koyun. 500 mikron 1000 mikron (M 500) arasında değişen altı tuz kesirler toplamak; 300 um, 500 um (M 300); 100 um ila 200 um (M 100); 90 um, 100 (M 90); Şekil 1'de şematize olarak 45 mikron tuz partikülleri ile 10 (M 45) um 65 …

Representative Results

Iskeleler gözenek mimarisinde NaCI partikül büyüklüğünün etkisinin altında örneklerinin morfolojisi araştırılması ve sırasıyla görüntü analizi ile, gözenek boyutu dağılımına hesaplanarak kalitatif ve kantitatif olarak tayin edilmiştir Şekil 2a -. F elde edilen mono-katmanlı iskeleler SEM mikrograflannı göstermektedir farklı NaCl parçacık boyutlarına içeren malzemelerin tuz süzülmesi. <p class="jove_content" fo:keep…

Discussion

ilk kritik adım verimliliğini eleme optimizasyonu olduğunu. NaCI parçacık boyutu, yüksek kontrol arzu edilen gözenek büyüklüğü dağılımına sahip iskele hazırlanması için temeldir. Diğer önemli adım kalıp numune çıkarma sırasında ince PLA mono tabakaları kırık kaçınmaktır. görüntü işleme analizi, tüm cihazın temsil etmiyor olabilir.

çekme testleri sırasında, numune ekipmandan uzak gözyaşı.

adım elekten geçirilmeden ön…

Materials

Poly(lactic acid)	NatureWorks	PLA 2002D
Poly(ethylene glycol)	Sigma	83797-1KG-F
Sodium Cloride	Sigma	793566-5KG-D
Phosfate Buffer Solution	Sigma	P5368-10PAK
Laboratory Mixer	Brabender	PLE 330 – Plasticorder
Laboratory Press	Carver
Scanning Electron Microscopy	Phenom-world	ProX
Universal Testing Machine	Instron	3365 (UK)
BioPuls Bath	Instron, Norwood
Sieving Machine	Endecotts	E.V.F.1.
Vacuum Oven	ISCO	NSV9035
Precision Balance	Sartorius	AX224