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The appropriate anti-adhesive effect of polymers on cells or tissues in the body is one of the essential requirements of maintaining health and protecting the body from trauma and foreign bodies. Regulating the anti-adhesive properties of biomedical polymers against cells has been considered a pivotal parameter in developing polymeric biomaterials for biomedical applications such as artificial blood vessels and cell encapsulation. Meanwhile, tissue adhesion barriers that can physically isolate wounds and thus effectively prevent the formation of tissue adhesion have been a hot topic in both research and industrial fields. This review describes the comprehensive knowledge and recent research efforts on polymers for anti-adhesion to both cells and tissues. The basic concepts and mechanisms for the design and performance of anti-adhesive polymers are introduced in terms of both cell and tissue. Polymer-based approaches for anti-adhesion to cells or tissues are then extensively discussed.

The potential for the clinical application of stem cells in tissue regeneration is clearly significant. However, this potential has remained largely unrealized owing to the persistent challenges in reproducibly, with tight quality criteria, and expanding and controlling the fate of stem cells in vitro and in vivo. Tissue engineering approaches that rely on reformatting traditional Food and Drug Administration-approved biomedical polymers from fixation devices to porous scaffolds have been shown to lack the complexity required for in vitro stem cell culture models or translation to in vivo applications with high efficacy. This realization has spurred the development of advanced mimetic biomaterials and scaffolds to increasingly enhance our ability to control the cellular microenvironment and, consequently, stem cell fate. New insights into the biology of stem cells are expected to eventuate from these advances in material science, in particular, from synthetic hydrogels that display physicochemical properties reminiscent of the natural cell microenvironment and that can be engineered to display or encode essential biological cues. Merging these advanced biomaterials with high-throughput methods to systematically, and in an unbiased manner, probe the role of scaffold biophysical and biochemical elements on stem cell fate will permit the identification of novel key stem cell behavioral effectors, allow improved in vitro replication of requisite in vivo niche functions, and, ultimately, have a profound impact on our understanding of stem cell biology and unlock their clinical potential in tissue engineering and regenerative medicine.

Biodegradable polyurethane elastomers (BioEPUR) are becoming increasingly important as biomaterials because they have excellent chemical, physico-mechanical and biological properties. This review presents the recent developments on BioEPUR and their potential applications in the biomedical and pharmaceutical fields. The aim of this work is to present an overview of the various methods of synthesis and properties of biomedical BioEPUR. Polyurethanes-based aliphatic or cycloaliphatic diisocyanates and polyesters, poly(ester-carbonate)s or copolymers of heterocyclic monomers were discussed.

Polymeric biomaterials have significant impact in the aged society. Biocompatible and biodegradable polymers have emerged during the past decades to promise extraordinary breakthroughs in a wide range of diagnostic and therapeutic medical devices. Understanding and controlling the interfacial interactions of the polymeric biomaterials with biological elements, such as water, ions, proteins, bacteria, fungai and cells, are essential toward their successful implementation in biomedical applications. Here we highlight the recent developments of biocompatible and biodegradable fusion polymeric biomaterials for medical devices and provide an overview of the recent progress of the design of the multi-functional biomedical polymers by controlling bio-interfacial water structure through precision polymer synthesis and supramolecular chemistry. Biocompatible and biodegradable polymers have emerged during the past decades to promise extraordinary breakthroughs in a wide range of diagnostic and therapeutic medical devices. Understanding and controlling the interfacial interactions of the polymeric biomaterials with biological elements are of essential towards their successful implementation in biomedical applications. Here, we highlight recent developments of biocompatible and biodegradable fusion polymeric biomaterials for medical devices and overview of the recent progress of the design of the multi-functional biomedical polymers by controlling biointerfacial water structure through precision polymer synthesis and supramolecular chemistry.

To evaluate the effects of ionic liquids (ILs) on the microstructural features of aliphatic polyesters for biomedical applications, a series of copolymers were synthesized by lipase ring opening polymerization of rac-lactide (rac-LA) and ε-caprolactone (CL). The chemical structures of resulting polymers were characterized by 1H- and 13C-NMR and the average molecular weight (Mn) and dispersity index were characterized by gel permeation chromatography. The structure of the copolymers confirms the presence of linear polymer chains with end-functional hydroxyl groups allowing covalent coupling of the therapeutic agents. Chain microstructure of copolymers indicates the presence of both random and block copolymers depending on the synthesis conditions. Moreover, it was found that CL is the most active co-monomer during copolymerization which enhances the polymerizability of rac-LA and allows to obtain higher Mn of the copolymers. The results demonstrate that ILs could be promising solvents in synthesis of aliphatic esters for biomedical applications.

Bio-based polymer hybrid composites hold a unique position in the fast-growing and active multidisciplinary world of biomaterials where engineers, scientists, and biologists combine their knowledge. It is well known that advances in science and engineering of biomaterials are crucial to solve complex medical and biomedical problems involving replacement, repair, and regeneration of tissues. This chapter covers the definition, importance, categorization, and application of polymer hybrid composites in the biomedical field. It is presented into two main parts. The first part includes the categorization of biomedical polymer hybrid composites, with information about the compositions and specifications of nanocomposites on the basis of hybridization of polymers with natural polymers, biopolymers, minerals, and metals. The second covers biomedical uses of polymer hybrid composites, considering their applications (i.e., drug delivery, tissue engineering, bioadhesion, etc.), and composition.

The paper is a literature review concerning the preparation and biomedical properties of polyurethanes for pharmaceutical applications. The basic uses of polyurethanes in pharmacy comprise modern drug formulations (including therapeutical systems, carriers and conjugates). Clinical studies indicate that the application of polymer—drug conjugates has a beneficial effect on the therapy efficacy. The introduction of such conjugates into the body results in an increase in drug therapeutic index as an effect of increased drug availability in the affected areas,while at the same time reducing systemic exposure to the drug.Owing to the application of polyurethane conjugates, it is also possible to reduce the side effects and toxicity of drugs. It is expected that the studies on macromolecular drug conjugates (including polyurethanes) will stimulate the development of modern forms of drugs and broadly defined medicinal chemistry.

Shape-memory effect (SME) is the ability of a material to change its dimension in a predefined way in response to an external stimulus. Polymers that exhibit SME are an important class of materials in medicine, especially for minimally invasive deployment of devices. However, the rate of translation of the concept to approved products is extremely low, with mostly nitinolbased devices being approved. In this review, the general aspects of the different types of stimuli that can be used to activate SME are reviewed and sterilization issues of shape-memory polymer (SMP)-based medical devices are addressed. In addition, the general usefulness as well as the limitations of the shape-memory effect for biomedical applications are described.

Background: Although various types of materials have been used widely in dialyzers, most biomaterials lack the desired functional properties to interface with blood and have not been engineered for optimum performance. Therefore, there is increasing demand to develop novel materials to address such problems in the dialysis arena. Numerous parameters of polymeric biomaterials can affect biocompatibility in a controlled manner. The mechanisms responsible for the biocompatibility of polymers at the molecular level have not been clearly demonstrated, although many theoretical and experimental efforts have been made to try and understand them. Moreover, water interactions have been recognized as fundamental for the blood response to contact with polymers. Summary: We have proposed the ‘intermediate water' concept and hypothesized that intermediate water, which prevents the proteins and blood cells from directly contacting the polymer surface, or nonfreezing water on the polymer surface, plays an important role in the biocompatibility of polymers. This chapter provides an overview of the recent experimental progress of biocompatible polymers measured by thermal, spectroscopic, and surface force techniques. Additionally, it highlights recent developments in the use of biocompatible polymeric biomaterials for dialyzers and provides an overview of the progress made in the design of multifunctional biomedical polymers by controlling the biointerfacial water structure through precision polymer synthesis. Key Messages: Intermediate water was found only in hydrated biopolymers (proteins, polysaccharides, and nucleic acids, DNA and RNA) and hydrated biocompatible synthetic polymers. Intermediate water could be one of the main screening factors for the design of appropriate dialyzer materials.

The past decade has seen growing interest in the investigation of peptides with antimicrobial activity (AMPs). One approach utilized in infection control is incorporation of antimicrobial agents conjugated with the polymers. This review presents the recent developments on polymeric AMP carriers and their potential applications in the biomedical and pharmaceutical fields.

Recent developments in polymer-based controlled delivery systems have made a significant clinical impact. The second Symposium on Innovative Polymers for Controlled Delivery (SIPCD) was held in Suzhou, China to address the key challenges and provide up-to-date progress and future perspectives in the innovation of polymer-based therapeutics. At SIPCD, a stimulating panel discussion was introduced for the first time on “What is the future of nanomedicine?” This report highlights the most recent research and developments in biomedical polymers and nanomedicine made by 29 invited scientists from around the world, as well as important issues regarding clinical advancements of nanomedicine conferred during the panel discussion.

Surface engineering using plasma, grafting, and related techniques is an important area in biomaterials research and biomedical engineering. The burgeoning technology enables the modification of selected surface characteristics while the favorable bulk materials properties can be retained. In this invited mini-review, recent work related to surface modification of biomaterials by plasma-based and related techniques conducted in the Plasma Laboratory at City University of Hong Kong is described. Examples of new applications include enhancement of antimicrobial properties and cytocompatibility of plasma and surface-treated and nanostructured biomaterials, corrosion resistance of plasma-treated biodegradable metals, as well as targeted drug delivery capability and magnetic properties of surface-modified silica nanospheres and polymeric micelles.

Polymers prepared by chemical vapor deposition (CVD) polymerization have found broad acceptance in research and industrial applications. However, their intrinsic lack of degradability has limited wider applicability in many areas, such as biomedical devices or regenerative medicine. Herein, we demonstrate, for the first time, a backbone-degradable polymer directly synthesized via CVD. The CVD co-polymerization of [2.2]para-cyclophanes with cyclic ketene acetals, specifically 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), results in well-defined, hydrolytically degradable polymers, as confirmed by FTIR spectroscopy and ellipsometry. The degradation kinetics are dependent on the ratio of ketene acetals to [2.2]para-cyclophanes as well as the hydrophobicity of the films. These coatings address an unmet need in the biomedical polymer field, as they provide access to a wide range of reactive polymer coatings that combine interfacial multifunctionality with degradability.

Functional aliphatic polycarbonates have attracted significant attention as materials for use as biomedical polymers in recent years. The incorporation of pendent functionality offers a facile method of modifying materials postpolymerization, thus enabling functionalities not compatible with ring-opening polymerization (ROP) to be introduced into the polymer. In particular, polycarbonates bearing alkene-terminated functional groups have generated considerable interest as a result of their ease of synthesis, and the wide range of materials that can be obtained by performing simple postpolymerization modifications on this functionality, for example, through radical thiol-ene addition, Michael addition, and epoxidation reactions. This review presents an in-depth appraisal of the methods used to modify alkene-functional polycarbonates postpolymerization, and the diversity of practical applications for which these materials and their derivatives have been used.

Significant advances in the field of polymer science over the past century have resulted in synthetic polymers becoming the basis for many new approaches to medical therapies and in particular development of new medical devices. While natural polymers have long been used in medicine and surgery, their application in medical devices has experienced a renaissance with advances in understanding of polymer synthesis and processing. In this chapter, natural polymers are discussed in detail, with a focus on proteins and polysaccharides. The major advantages and disadvantages in relation to use of natural polymers are considered with an emphasis on the key factors impacting their biological performance in tissue contacting devices. Approaches to developing hybrid materials that combine the advantages of both natural and synthetic polymers are becoming increasingly topical and hold much promise for the future of medical devices that can integrate with and drive regeneration of tissues.

Polymers are the most multifaceted class of biomaterials that are routinely being used for biomedical applications ranging from surgical sutures to tissue engineering scaffolds, medical implants, and drug-eluting devices.

One of the reasons that polymers are important in biomedical applications is the ease with which they can be processed in comparison with metals and ceramics. Well-established methods practiced in the plastics industry for processing commodity and engineering polymers can be used to fabricate biomedical devices and scaffolds. Methods are also being developed to accommodate the special characteristics of biomedical polymers, such as for instance processing of degradable polymers that require additional precautions. Degradable polymers require water free environment, mild thermal processing conditions, and precise temperature controls. Solvent based processing is therefore preferred to avoid degradation and to incorporate drug and bioactives.

As discussed in Chap. 1, polymeric biomaterials of both natural and synthetic origin constitute an important class of biomedical materials that are used extensively in various applications ranging from drug delivery to tissue engineering. The use of natural polymers such as cellulose and collagen for various medical applications dates back to centuries.

Nowadays, polymers are finding increasing use in a bewildering array of specialist applications. A good example of this is in the biomedical field. In this paper, some of the research work which is being carried out in Chiang Mai will be described. In its wider context, this paper also aims to show how the development of new polymers for such specialist applications depends on being able to control the polymers microstructure at each stage of its synthesis and processing.

This chapter presents an overview of the current knowledge on experimental methods for monitoring the biodegradability of polymeric materials. The focus is, in particular, on the biodegradation of materials under environmental conditions. Examples of in vivo degradation of polymers used in biomedical applications are not covered in detail but have been extensively reviewed elsewhere, e.g., [1 – 3] . Nevertheless, it is good to realize that the same principles of the methods for monitoring biodegradability of environmental polymers are also used for the evaluation of the degradation behavior of biomedical polymers. A number of different aspects of assessing the potential, the rate, and the degree of biodegradation of polymeric materials are discussed. The mechanisms of polymer degradation and erosion receive attention and factors affecting enzymatic and nonenzymatic degradation are briefl y addressed. Particular attention is given to the various ways for measuring biodegradation, including complete mineralization to gasses (such as carbon dioxide and methane), water, and possibly microbial biomass. Finally, some general conclusions are presented with respect to measuring biodegradability of polymeric materials.

Water uptake influences many properties of polymers and has been widely studied. In the context of polymeric biomaterials, several publications reported an unusual high variability of analytical results, without further investigating the cause for this phenomenon. Using selected polymers from the library of L-tyrosine-derived polyarylates and poly(D,L lactic acid), we showed that nonaged and nonannealed compression molded film samples exhibit the typical large variation in water uptake observed in previous reports. The introduction of an annealing step allows accurate and reproducible water uptake measurements for these polymers. We evaluated the use of 3H-radiolabeled water for the determination of water uptake, finding that the use of radiolabeled water yields statistically indistinguishable measurements, compared to gravimetric methods, while providing significant advantages in throughput and sensitivity. Using the recommended methods of annealing and 3H-radiolabled water, the water uptake profiles of 24 polymers of the library of L-tyrosine-derived polyarylates are reported. This article addresses experimental concerns related to water uptake studies and may assist other researchers in improving the accuracy of their water uptake results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthetic polymer hydrogels constitute a group of materials, used in numerous biomedical disciplines, and are still developing for new promising applications. The aim of this study is to review information about well known and the newest hydrogels, show the importance of water uptake and cross-linking type and classify them in accordance with their chemical structure. Синтетичні полімерні гідрогелі являють собою групу біоматеріалів, які вже використовуються в чисельних біомедичних галузях, і які розробляються для нового перспективного застосування. В роботі проаналізовано інформацію як про відомі, так і новітні гідрогелі. Показано, наскільки важливими є здатність до водопоглинання і тип структурування, а також проведено класифікацію гідрогелів відповідно до їх хімічної структури.

A novel organosilicon sulfobetaine was synthesized through the reaction of organosilicon containing tertiary amino with 1,3-propanesulfone. Then this organosilicon sulfobetaine was coated onto polyurethane and organosilicon surface to improve their blood compatibility. The existence of sulfobetaine structure on the surface of materials was revealed by ATR-FTIR and XPS. The thermo-capability of synthesized silicone rubber, containing sulfobetaine was revealed by TGA. The blood compatibilities of organosilicon sulfobetaine and other materials such as silicone and PU as reference coated with them were evaluated by platelet-rich plasma adhesion experiment. The novel segmented silicone rubber containing sulfobetaine structure showed perfect blood compatibility.

The synthesis of the aliphatic polyesters — polylactide (PLA) and poly (e-caprolactanes) (PCL) in the ring-opening polymerization of cyclic esters in the presence tin(II) 2-ethylhexanoate (SnOct 2 ) has been presented. The obtained products were subjected to multiple purification procedures to remove residual organo-tin catalyst (Tables 2 and 3). The tin content in the polyesters was then determined by Electrothermal Atomic Absorption Spectroscopy (ET-AAS) (Tables 3 and 4) after each purification process. The results of the analysis were discussed taking into consideration the requirements placed by the European Pharmacopoeia regarding the amount of tin allowed in aliphatic biomedical polyesters. It was confirmed, that a four-stage purification of the polyreaction product led to a three-fold decrease in the concentration of tin to a level less than the value required by Pharmacopoeia for materials designated for contact with blood. Moreover, the purification process did not generate any degradation of the polymer.

A recently developed electrohydrodynamic printing method is described that can be used to create ordered structures and complex patterns using coarse processing needles and two polymeric materials. The results highlight the method's potential for direct 3D writing of biomedical polymers and composites for a variety of biomedical applications.

Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental understanding of polymer-nanoparticle interactions is absolutely necessary to control structure-property relationships of materials that need to work within the chemical, physical and biological constraints required by an application. This review summarizes the most recent published strategies to design and develop polymer-silicate nanocomposites (including clay based silicate nanoparticles and bioactive glass nanoparticles) for a variety of biomedical applications. Emerging trends in bio-technological and biomedical nanocomposites are highlighted and potential new fields of applications are examined.

The nature of plasma-induced surface radicals formed on a variety of organic polymers have been studied by electron spin resonance (ESR), making it possible to provide a sound basis for future experimental design of polymer surface processing using plasma treatment. On the basis of the findings from such studies, several novel bio-applications in the field of drug- and biomedical- engineering have been developed. Applications for drug engineering include the preparation of reservoir-type drug delivery system (DDS) of sustained- and delayed-release, and floating drug delivery system (FDDS) possessing gastric retention capabilities, followed by preparation of "Patient-Tailored DDS". Furthermore, the preparation of composite powders applicable to matrix-type DDS was developed by making a mechanical application to the surface radical-containing polymer powders with drug powders. In applications for biomedical engineering, the novel method to introduce the durable surface hydrophilicity and lubricity on hydrophobic biomedical polymers was developed by plasma-assisted immobilization of carboxyl group-containing polymer on the polymer substrate. The surfaces thus prepared were further used for the covalent immobilization of oligo-nucleotides (DNA) onto the polymer surfaces applicable to constructing DNA diagnosis system, and also plasma-assisted preparation of functionalized chemo-embolic agent of vinyl alcohol-sodium acrylate copolymer (PVA- PAANa).

Silk is a textile material, as well as one of the oldest biomaterials. However, the recent progress of biomedical science and technology has led to the replacement of silk by various biomaterials based on synthetic polymers. Despite the wide variety of biomaterials available, these materials suffer certain limitations that prevent them from meeting the various demands of the medical field. Therefore, silk continues to attract considerable interest as a promising biomaterial. This paper explains the fundamentals of silk protein, and reviews the many applications of silk biomedical polymers.

Poly(lactic-co-glycolic) acid (PLGA) is one of the most versatile biomedical polymers, already approved by regulatory authorities to be used in human research and clinics. Due to its valuable characteristics, PLGA can be tailored to acquire desirable features for control bioactive payload or scaffold matrix. Moreover, its chemical modification with other polymers or bioconjugation with molecules may render PLGA with functional properties that make it the Holy Grail among the synthetic polymers to be applied in the biomedical field. In this review, the physical-chemical properties of PLGA, its synthesis, degradation, and conjugation with other polymers or molecules are revised in detail, as well as its applications in drug delivery and regeneration fields. A particular focus is given to successful examples of products already on the market or at the late stages of trials, reinforcing the potential of this polymer in the biomedical field.

Hydrogels were the first biomaterials designed for clinical use. Their discovery and applications as soft contact lenses and implants are presented. This early hydrogel research served as a foundation for the expansion of biomedical polymers research into new directions: design of stimuli sensitive hydrogels that abruptly change their properties upon application of an external stimulus (pH, temperature, solvent, electrical field, biorecognition) and hydrogels as carriers for the delivery of drugs, peptides, and proteins. Finally, pathways to self-assembly of block and graft copolymers into hydrogels of precise 3D structures are introduced.

In order to investigate poly(N-vinyl pyrrolidone) as an alternative to poly(ethylene glycol) in preparing a biomedical polymer, we synthesized a series of reverse thermogelling poly(N-vinyl pyrroli...

Intelligent polymers or stimuli-responsive polymers may exhibit distinct transitions in physical-chemical properties, including conformation, polarity, phase structure and chemical composition in response to changes in environmental stimuli. Due to their unique ‘intelligent’ characteristics, stimuli-sensitive polymers have found a wide variety of applications in biomedical and nanotechnological fields. This review focuses on the recent developments in biomedical application of intelligent polymer systems, such as intelligent hydrogel systems, intelligent drug delivery systems and intelligent molecular recognition systems. Also, the possible future directions for the application of these intelligent polymer systems in the biomedical field are presented.

The sol-gel derived bioactive glass short fibers in the system CaO-P2O5-SiO2 was prepared using air-spray method. SBF immersion test indicated that the fibers possessed satisfactory bioactivity. SEM, XRD, FTIR analysis revealed that the morphologies and bioactivity of the fibers could be significantly influenced by the composition and viscosity of the solution. The fibers are very promising biomaterials for applications to bone restoration and tissue engineering as the bone defects fillers or additives for strengthening of the biomedical polymers.

The purpose of this communication is to present the author's perspectives on the future of biomedical materials that were presented at the Larry L. Hench Retirement Symposium held at Imperial College, London, in late September 2005. The author has taken a broad view of the future of biomedical materials and has presented key ideas, concepts, and perspectives necessary for the future research and development of biomedical polymers and their future role as an enabling technology for the continuing progress of tissue engineering, regenerative medicine, prostheses, and medical devices. This communication, based on the oral presentation, is meant to be provocative and generate discussion. In addition, it is targeted for students and young scientists who will play an ever-increasing role in the future of biomedical materials.

8 páginas, 6 figuras, 2 esuqemas, 4 tablas., Bioresorbable linear poly(ester-ether urethane)s with different hydrophilic character were synthesized from block copolymers of poly(ϵ-caprolactone)-poly(ethylene oxide)-poly(ϵ-caprolactone) (PCL-PEO-PCL) as macrodiols, and L-lysine diisocyanate (LDI). A series of PCL-PEO-PCL triblock copolymers with different PEO and PCL chain length was obtained by reacting PEO with ϵ-caprolactone. Polyurethanes were synthesized by reacting the triblock copolymers with LDI in solution using stannous 2-ethylhexanoate as catalyst. The prepared triblock copolymers and polyurethanes were fully characterized by proton nuclear magnetic resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. Water uptake, hydrolytic stability, and tensile properties of polyurethanes with different composition were evaluated and discussed in terms of the chain length and molecular weight of the polymers and its block components. Water uptake seems to depend on the ethylene oxide unit content of the polyurethane regardless of the triblock structure. Mechanical properties of the synthesized polymers were strongly affected by the molecular weight achieved during polymerization. The use of triblock macrodiols with different hydrophilicity allowed the preparation of a series of polyurethanes having a broad range of properties., The donation of LDI from Kyowa Hakko Kogyo Co. Ltd (Japan), the partial support of MAT2001/1634 project, Fundación ANTORCHAS and CONICET (Argentina) are gratefully acknowledged.

The aim of this study was to coat bioactive glass 13-93 fibres with biomedical polymers. Two methods were used to coat the fibres, namely, dipping and pulling through a viscous solution. With both methods the fibres were successfully coated. Dipping was preferred for thin fibres (20–50 μm) and with this method approximately 2–5 μm thin polymer coat was obtained on the fibre surface. Pulling through viscous solution was preferred for thicker fibres (150–250 μm) and with this method approximately 10–30 μm polymeric coat was obtained. Coating the fibres enables further processing of the bioactive glass fibres and improves the mechanical properties and processibility of fibres.

Biofilm formation on biomaterials implant surfaces and subsequent infectious complications are a frequent reason for failure of many biomedical devices, such as total hip arthroplasties, vascular catheters and urinary catheters. The development of a biofilm is initiated by the formation of a conditioning film of adsorbed macromolecules, such as proteins, followed by adhesion of microorganisms, where after they grow and anchor through secretion of extracellular polymeric substances. Adhesion of microorganisms is influenced by the physico-chemical properties of the biomaterial surface. Positively charged materials stimulate bacterial adhesion, but prevent growth of adhering bacteria. The use of low surface free energy materials did not always reduce in vitro adhesion of bacteria, but has been found beneficial in in vivo applications where fluctuating shear forces prevail, like on intra-oral devices and urine catheters. Polymer brushes have shown a very high reduction in in vitro adhesion of a great variety of microorganisms. However, for clinical application, the long term stability of polymer brushes is still a limiting factor. Further effort is therefore required to enhance the stability of polymer brushes on biomaterial implant surfaces to facilitate clinical use of these promising coatings

The field of biomedical dendrimers is still in its infancy, but the explosion of interest in dendrimers and dendronised polymers as inherently active therapeutic agents, as vectors for targeted delivery of drugs, peptides and oligonucleotides, and as permeability enhancers able to promote oral and transdermal drug delivery makes it timely to review current knowledge regarding the toxicology of these dendrimer chemistries (currently under development for biomedical applications). Clinical experience with polymeric excipients, plasma expanders, and most recently the development of more 'classical polymer'-derived therapeutics can be used to guide development of "safe" dendritic polymers. Moreover, in future it will only ever be possible to designate a dendrimer as "safe" when related to a specific application. The so far limited clinical experience using dendrimers make it impossible to designate any particular chemistry intrinsically "safe" or "toxic". Although there is widespread concern as to the safety of nano-sized particles, preclinical and clinical experience gained during the development of polymeric excipients, biomedical polymers and polymer therapeutics shows that judicious development of dendrimer chemistry for each specific application will ensure development of safe and important materials for biomedical and pharmaceutical use.

This work presents the challenges and directions in biomaterials research. Biomaterials have been playing an important role in the treatment of disease and the improvement of healthcare. Metals were used in dentistry while synthetic polymers have been used for vascular grafts; polymethylmethacrylate and stainless steel have been used in total hip replacements. Controlled drug delivery systems largely involve biomedical polymers and are used by tens of million of people annually. Furthermore, in tissue engineering, by combining polymers with mammalian cells, it is now possible to engineer skin for patients who have burns or skin ulcers. Until recently, biomaterials were adopted from other areas of science and technology with little design for biomedical use, which did not help to completely resolve issues in biocompatibility, mechanical properties, degradation, etc. Modern biomaterial science is laying the foundation for a fundamental design by taking into consideration cell-matrix interactions, cellular signaling processes, and developmental biology. Concepts that are shaping future directions are biomaterials for specific biomedical applications made from naturally occurring or man-made building blocks or novel applications for biomaterials, such as diagnostics and array technologies.

A variety of bioactive composites have been investigated over the last two decades as substitute materials for diseased or damaged tissues in the human body. In this paper, the rationale and strategy of developing these composites are given. Major factors influencing the production and performance of bioactive composites are discussed. Some promising composites for tissue replacement and regeneration are reviewed. On the basis of past experience and newly gained knowledge, composite materials with tailored mechanical and biological performance can be manufactured and used to meet various clinical requirements.

Impressive advances in biotechnology, bioengineering, and biomaterials with unique properties have led to increased interest in polymers and other novel materials in biological and biomedical research and development over the past two decades. Although biomaterials have already made an enormous impact in biomedical research and clinical practice, there is a need for better understanding of the surface and interfacial chemistry between tissue (or cells) and biomedical materials. This is because the detailed physicochemical events related to the biological response to the surface of materials still often remain obscure, even though surface properties are important determinants of biomedical material function. In this regard, data available in the literature show the complexity of the interactions (surface reorganization, non-specific/specific protein adsorption, and chemical reactions such as acid-base, ion pairing, ion exchange, hydrogen bonding, divalent-ion bridging) and the interrelationship between biological environments, interfacial properties, and surface functional groups responsible for the biological responses. Because of the multidisciplinary nature of surface and interfacial phenomena at the surface of biomedical polymers, this review focuses on several aspects of current work published on poly(alpha-hydroxy acid)s and their associated copolymers:surface structure-biomedical function relationships;physicochemical strategies for surface modification; and, finally,synthetic strategies to increase biocompatibility for specific in-vivo and/or in-vitro biomedical applications.