Surface modification of starch based biomaterials by oxygen plasma or UV-irradiation

Radiation is widely used in biomaterials science for surface modification and sterilization. Herein, we describe the use of plasma and UV-irradiation to improve the biocompatibility of different starch-based blends in terms of cell adhesion and proliferation. Physical and chemical changes, introduced by the used methods, were evaluated by complementary techniques for surface analysis such as scanning electron microscopy, atomic force microscopy, contact angle analysis and X-ray photoelectron spectroscopy. The effect of the changed surface properties on the adhesion of osteoblast-like cells was studied by a direct contact assay. Generally, both treatments resulted in higher number of cells adhered to the modified surfaces. The importance of the improved biocompatibility resulting from the irradiation methods is further supported by the knowledge that both UV and plasma treatments can be used as cost-effective methods for sterilization of biomedical materials and devices.I. P. thanks the FCT for providing her a postdoctoral scholarship (SFRH/BPD/8491/2002). This work was partially supported by FCT, through funds from the POCTI and/or FEDER programs, The European Union funded STREP Project HIPPOCRATES (NNM-3-CT-2003-505758) and the European NoE EXPERTISSUES (NMP3-CT-2004-500283)

Fabrication and characterisation of organic thin films for applications in tissue engineering: emphasis on cell-surface interactions

In several recent communications from these laboratories, we have described observations that thin organic layers which are rich in primary amine (R-NH2) groups are very efficient surfaces for the adhesion of mammalian cells, even for controlling the differentiation of stem cells. We prepare such deposits by plasma polymerization at low pressure (thin films designated "L-PPE:N", for "Low-pressure Plasma Polymerized Ethylene containing Nitrogen"), at atmospheric ("High") pressure ("H-PPE:N"), or by vacuum-ultraviolet photo-polymerization ("UV-PE:N"). More recently, we have also investigated a commercially available material, Parylene diX AM. In the present communication we shall, first, briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. Next, we discuss the comparative results of physico-chemical characterizations of the various organic deposits mentioned above, which deliberately contain varying concentrati ons of nitrogen, [N], and amine groups, [NH2]. Finally, we present certain selected cell-response results that pertain to applications in orthopedic medicine; we discuss the influence of surface properties on the observed behaviors of various cell lines, with particular emphasis on possible electrostatic attractive forces due to positively charged R-NH3 + groups and negatively charged proteins and cells, respectively

Adhesion of U937 monocytes on polymer surfaces: Chemistry or electrostatics?

There exists a large body of published literature, some going back several decades, that points to electrostatic (i.e. physical) adhesive forces between biomaterials surfaces and living cells, as opposed to chemical ones. Nevertheless, in view of the inherent complexity of biological phenomena, including cell biology, it is rarely simple to be able to separate them unambiguously, as we hope to have illustrated here

Caged [18F]FDG Glycosylamines for Imaging Acidic Tumor Microenvironments Using Positron Emission Tomography

Solid tumors are hypoxic with altered metabolism, resulting in secretion of acids into the extracellular matrix and lower relative pH, a feature associated with local invasion and metastasis. Therapeutic and diagnostic agents responsive to this microenvironment may improve tumor-specific delivery. Therefore, we pursued a general strategy whereby caged small-molecule drugs or imaging agents liberate their parent compounds in regions of low interstitial pH. In this manuscript, we present a new acid-labile prodrug method based on the glycosylamine linkage, and its application to a class of positron emission tomography (PET) imaging tracers, termed [(18)F]FDG amines. [(18)F]FDG amines operate via a proposed two-step mechanism, in which an acid-labile precursor decomposes to form the common radiotracer 2-deoxy-2-[(18)F]fluoro-D-glucose, which is subsequently accumulated by glucose avid cells. The rate of decomposition of [(18)F]FDG amines is tunable in a systematic fashion, tracking the pK(a) of the parent amine. In vivo, a 4-phenylbenzylamine [(18)F]FDG amine congener showed greater relative accumulation in tumors over benign tissue, which could be attenuated upon tumor alkalinization using previously validated models, including sodium bicarbonate treatment, or overexpression of carbonic anhydrase. This new class of PET tracer represents a viable approach for imaging acidic interstitial pH with potential for clinical translation