Polymers For Biomedical Applications Research Articles

Nanoparticles of conjugated polymers prepared from phase-separated films of phospholipids and polymers for biomedical applications.

Phase separation in films of phospholipids and conjugated polymers results in nanoassemblies because of a difference in the physicochemical properties between the hydrophobic polymers and the polar lipid heads, together with the comparable polymer side-chain lengths to lipid tail lengths, thus producing nanoparticles of conjugated polymers upon disassembly in aqueous media by the penetration of water into polar regions of the lipid heads.

Physico-chemical, mechanical and cytotoxicity characterizations of Laponite®/alginate nanocomposite

Combining clay minerals containing silica with polymers can improve the performance of polymers in biomedical applications by the synergistic combination of physico-chemical and biological properties of both phases. In this study, Laponite® — a synthetic biocompatible and biodegradable silicate clay mineral, was combined with alginate to improve alginate mechanical and biological characteristics. The physico-chemical properties (porosity, degradation, swelling, crystalline structure, compressive strength, and injectability) and biological responses (cytotoxicity and cell morphology) of the Laponite/alginate nanocomposites were investigated in the study. The results showed that the incorporation of Laponite into alginate significantly enhanced alginate compression strength without hindering its injectability when the percentage of clay mineral was below 50%. The prepared clay polymer nanocomposites (CPN) were not toxic and the viability of cells cultured in its extract was indeed higher than alginate alone. However, these prepared CPN poorly supported cell adhesion, probably due to the high degradation rate of the materials.

Polymers for biomedical applications

Polymers for biomedical applications

Capping Gold Nanoparticles with Modified Chitosan Polymers for Biomedical Applications

Capping Gold Nanoparticles with Modified Chitosan Polymers for Biomedical Applications

Deep eutectic solvents as both active fillers and monomers for frontal polymerization

AbstractThe deep eutectic solvents (DESs) based on the mixtures of a variety of ammonium salts and hydrogen bond donors containing acrylic acids and acrylamides are capable of sustaining frontal polymerization (FP). The selection of ammonium salt affects the reactivity and allows FP at relatively low temperature but with full conversion. Also, full conversion allows us to use these polymers for biomedical applications (e.g., drug delivery systems) as the unreactive ammonium salts can be released from the resulting polymer without by‐products. We call these components “active fillers,” which can be ammonium salts with biological or pharmaceutical importance. For instance, we prepared poly(acrylic acid) loaded with lidocaine hydrochloride (a common anesthetic), the release of which was found to occur in a controlled fashion. The ammonium salts also create a sufficiently high viscosity to suppress buoyancy‐driven convection without additional materials. The DES here described played an all‐in‐one role, providing the monomer, the active filler, and the polymerization medium for FPs. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Biodegradable device applied in flatfoot surgery: Comparative studies between clinical and technological aspects of removed screws

Poly-l-lactide (PLLA) is one of the most used polymers for biomedical application; its use in sutures and other implants has been widely investigated. Although the knowledge of PLLA biodegradation and biocompatibility features is deep, PLLA screws used to correct the flat foot deformity have deserved attention since they are not degraded in most of cases after a long period of years (3–7) from the implantation. In this article, a clinical and radiological evaluation (NMR, histological and clinical outcomes) on patients was correlated with physico-chemical characterization (by SEM, DSC, GPC and XRD analysis at different temperatures) on both native and patient-recovered screws together with the theoretical degradation processes of PLLA-based implants. The data demonstrated the need for crossing the biodegradation and bioabsorption of the polymer with the characteristics of both the device (geometry, structure and fabrication process) and the implantation site.

Antimicrobial polymers as synthetic mimics of host‐defense peptides

Antibiotic-resistant bacteria 'superbugs' are an emerging threat to public health due to the decrease in effective antibiotics as well as the slowed pace of development of new antibiotics to replace those that become ineffective. The need for new antimicrobial agents is a well-documented issue relating to world health. Tremendous efforts have been given to developing compounds that not only show high efficacy, but also those that are less susceptible to resistance development in the bacteria. However, the development of newer, stronger antibiotics which can overcome these acquired resistances is still a scientific challenge because a new mode of antimicrobial action is likely required. To that end, amphiphilic, cationic polymers have emerged as a promising candidate for further development as an antimicrobial agent with decreased potential for resistance development. These polymers are designed to mimic naturally occurring host-defense antimicrobial peptides which act on bacterial cell walls or membranes. Antimicrobial-peptide mimetic polymers display antibacterial activity against a broad spectrum of bacteria including drug-resistant strains and are less susceptible to resistance development in bacteria. These polymers also showed selective activity to bacteria over mammalian cells. Antimicrobial polymers provide a new molecular framework for chemical modification and adaptation to tune their biological functions. The peptide-mimetic design of antimicrobial polymers will be versatile, generating a new generation of antibiotics toward implementation of polymers in biomedical applications.

Editorial [Hot Topic: Dendrimers in Biomedical Applications

Dendrimers as antiamyloidogenic agents Dendrimer-amyloid aggregates morphology and cell toxicity dendrimer-based hybrid fibers as potential platform for 1d-objects in nanotechnology natural and synthetic biomaterials as composites of advanced drug delivery nano systems (addnss). Biomedical applications cationic carbosilane dendrimers as non-viral vectors of nucleic acids (oligonucleotide or sirna) for gene therapy purposes anionic dendritic polymers for biomedical applications dendrimers as nanovectors for nucleic acid delivery dendrimeric antigens. New approaches towards detection of ige-mediated drug allergy reactions molecular dynamics of lysine dendrimers. Computer simulation and nmr characterization of dendrimers and their interactions with biomolecules for medical use by means of electron magnetic resonance dendrimers as vectors for small interfering rna transfection in the nervous system multiscale modeling of dendrimers and dendrons for drug and nucleic acid delivery poly(aminoester) dendrimers: design, synthesis and characterization from multivalent dendrons to self-asssembled multivalent dendrimers: a combined experimental and theoretical approach

Mapping the Influence of Solubility and Dielectric Constant on Electrospinning Polycaprolactone Solutions

Solvent–polymer interactions critically influence not only the viscoelasticity and the critical minimum solution concentration required for electrospinning but also the diameter, crystallinity, tensile strength, aspect ratio, and morphology of the electrospun fibers. Hence, a good understanding of the solvents and nonsolvents available and electrospinnable for a polymer of interest is important. The electrospinnability–solubility map uniquely presents the solubility and the electrospinnability of all solvents for a polymer in a single figure. Poly(ε-caprolactone) (PCL), an important polymer in biomedical applications, has been electrospun in a few conventional solvent systems, but a comprehensive mapping of its solvents for electrospinning has not been performed. Based on 49 common solvents of diverse solubility parameters and functional groups, the spinnability–solubility graph for electrospinning PCL solutions was mapped for the first time to enable a comprehensive understanding of the processability of all solvent choices for electrospinning PCL solutions. Furthermore, to date, many studies have demonstrated the importance of the dielectric constant (relative permittivity) of solvents in solution electrospinning, but few have systematically investigated its influence for a broad range of solvent systems. Based on the comprehensive PCL solvent map, this work studies the influence of dielectric constant of solvent systems on the electrospinning of PCL solutions. PCL (Mn = 80 000 g/mol) fiber diameters <100 nm were achieved when the dielectric constant of a solvent system was ∼19 and above, below which fibers or relics of diameters from submicrometer to millimeter range were produced. A detailed investigation was carried out on solvent systems with a calculated range of dielectric constants by mixing acetic acid and formic acid—two solvents with significantly different dielectric constants but the same functional group and comparable in other physical properties influential in electrospinning. With increasing dielectric constant, the required applied voltage to achieve stable jetting increased, the frequency of bead-on-string morphology decreased, and the interfiber spacing increased without affecting the total mass of fibers spun per unit time. In addition, the dissolution and electrospinnability of poor or nonsolvents of PCL were tested at temperatures 10 °C or higher than the ambient temperature. A unique and novel morphology of electrospun fibers within electrosprayed relics was generated for the first time when electrospinning PCL in 2-ethoxyethyl acetate, a nonsolvent at an ambient temperature of 20–22 °C and a partial solvent of PCL at an elevated temperature of above 30 °C.

Biosynthesis of highly pure poly-γ-glutamic acid for biomedical applications

The remarkable properties of poly-aminoacids, mainly their biocompatibility and biodegradability, have prompted an increasing interest in these polymers for biomedical applications. Poly-γ-glutamic acid (γ-PGA) is one of the most interesting poly-aminoacids with potential applications as a biomaterial. Here we describe the production and characterization of γ-PGA by Bacillus subtilis natto. The γ-PGA was produced with low molecular weight (10-50kDa), high purity grade (>99%) and a D: -/L: -glutamate ratio of 50-60/50-40%. To evaluate the feasibility of using this γ-PGA as a biomaterial, chitosan (Ch)/γ-PGA nanoparticles were prepared by the coacervation method at pH ranging from 3.0 to 5.0, with dimensions in the interval 214-221nm with a poly-dispersion index of ca. 0.2. The high purity of γ-PGA produced by this method, which is firstly described here, renders this biopolymer suitable for biomedical applications. Moreover, the Ch/γ-PGA nanocomplexes developed in this investigation can be combined with biologically active substances for their delivery in the organism. The fact that the assembly between Ch and γ-PGA relies on electrostatic interactions enables addition of other molecules that can be released into the medium through changes from acidic to physiological pH, without loss in biological activity.

Thermal Characterization of Novel Polymers for Biomedical Applications

Thermal Characterization of Novel Polymers for Biomedical Applications

Molecularly imprinted polymers in drug delivery: state of art and future perspectives

Introduction:Molecularly imprinted polymers (MIPs) are synthetic receptors, characterized by a high selectivity for the selected template. Among the different applications of MIPs, their use as controlled/sustained drug delivery devices has been extensively explored, even though the optimization of such devices needs to be performed before they are applied in clinical practice.Areas covered:Within drug delivery, one of the most promising fields is the possibility to modulate the drug release profile in response to a specific external stimulus; MIPs represent potentially suitable vehicles, because of the possibility to insert a stimuli-responsive co-monomer in their structure. This review discusses recent advances in the use of external stimuli to modulate drug release, as well as the synthetic strategies devoted to increase the water compatibility of these systems, which is a base requirement for their application in biomedicine.Expert opinion:Although it is easy to imagine imprinted polymers for biomedical applications, several aspects have to be further investigated, such as the in vivo studies, efficiency and biocompatibility. However, we think that in the next few years it will possible to see unprecedented progress in the preparation of such systems and the translational application of these intelligent structures in medicine.

“Click” Synthesis of Fatty Acid Derivatives as Fast‐Degrading Polyanhydride Precursors

Fast-degrading linear and branched polyanhydrides are obtained by melt-condensation of novel di- and tri-carboxylic acid monomers based on oleic and undecylenic acid synthesized using photoinitiated thiol-ene click chemistry. (1)H NMR spectroscopy, size exclusion chromatography, differential scanning calorimetry, thermogravimetric analysis, and FT-IR spectroscopy have been used to fully characterize these polymers. The hydrolytic degradation of these polymers was studied by means of weight loss, anhydride bond loss, and changes in molecular weight, showing fast degrading properties. Drug release studies from the synthesized polyanhydrides have also been conducted, using rhodamine B as a hydrophobic model drug, to evaluate the potential of these polymers in biomedical applications.

Overcoming the PEG-addiction: well-defined alternatives to PEG, from structure–property relationships to better defined therapeutics

Synthetic methods in polymer chemistry have evolved tremendously during the last decade. Nowadays more and more attention is devoted to the application of those tools in the development of the next generation of nanomedicines. Nevertheless, poly(ethylene glycol) (PEG) remains the most frequently used polymer for biomedical applications. In this review, we try to summarize recent efforts and developments in controlled polymerisation techniques that may allow alternatives to PEG based systems and can be used to improve the properties of future polymer therapeutics.

Modeling of Deformation-Accelerated Breakdown of Polylactic Acid Biodegradable Stents

The use of biodegradable polymers in biomedical applications has been successful in nonload bearing applications, such as biodegradable implants for local drug delivery, and in simple load bearing situations such as surgical sutures and orthopedic fixation screws. The desire to incorporate these materials in more complex load bearing situations, such as tissue engineering scaffolds and endovascular or urethral stents, is strong, but the lack of constitutive models describing the evolution of biodegradable polymers over the course of degradation has severely hampered the rational design process for these more complex biodegradable medical applications. With the objective of predicting biodegradable stent behavior, we incorporated constitutive models of biodegradable polymeric materials in a computational setting and the mechanical response of three different stent designs were analyzed as degradation progressed. A thermodynamically consistent constitutive model for materials undergoing deformation-induced degradation was applied to a commonly employed biodegradable polymer system, poly(L-lactic acid), and its specific form was determined by corroboration against experimental data. Depreciation of mechanical properties due to degradation confers time-dependent characteristics to the response of the biodegradable material: the deformation imparted by a constant load increases over time, i.e. the body creeps, and the stress necessary to keep a fixed deformation decreases, i.e. the body relaxes. Biodegradable stents, when subjected to constant pressure in its exterior, deflect inwards and ultimately fail as the structure loses its mechanical integrity. The complex geometry of endovascular stents and their physiological loading conditions lead to inhomogeneous deformations, and consequently, inhomogeneous degradation ensues. Degradation is mostly confined to the bends of the stent rings and junction points, which are the locations that carry most of the deformation, whereas mostly undeformed connector bars remain less degraded. If failure occurs, it will occur most likely at those sensitive locations and large, nondegraded pieces can provoke severe embolic problems. Highly nonuniform degradation indicates that some stent designs are at higher risk for complications. Deformation patterns of stents made of a material that loses its integrity are different than those of permanent stents. Blind adaptation of permanent stent design concepts is ill-suited for biodegradable stent design. The time-dependent aspect of the implant not only must be taken into account but should also be used to interact with the body’s reaction and to enhance healing.

Polymers for Biomedical Applications

Polymers for Biomedical Applications

Bioapplications of Networks Based on Photo‐Cross‐Linked Hyperbranched Polymers

AbstractThis article deals with some of the most recent developments in the use of hyperbranched polymers in biomedical applications. Some examples have been selected to show their potential in drug delivery, tissue engineering, imaging technologies and molecular imprinting. Moreover, the preparation of methacrylic networks using chemically‐modified hyperbranched polymers as multifunctional macromonomers by photopolymerization is described. The capability to support valve interstitial cell culture was demonstrated and the adhesion and functionality of the cells was related to the mechanical properties of these materials.

Synthesis and properties of block poly(ether-ester)s based on poly(ethylene oxide) and various hydrophobic segments

To obtain biodegradable amphiphilic block polymers for biomedical applications, a series of poly(ether-ester)s based on poly(ethylene oxide) and various hydrophobic/hydrophilic segment ratios were synthesized by the solution polymerization technique. The polyesters were characterized using 1H NMR spectroscopy, elemental analysis, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and compression stress–strain measurements. The composition of the poly(ether-ester)s agreed with the feed ratio. A study of the degree of phase segregation in the polymers evidenced that microphase mixing increases with the presence in the hydrophobic segments of polar groups able to establish interactions with the poly(ethylene oxide). This phase mixing increased the thermal stability of the acidic poly(ether-ester)s. Nanospheres for drug delivery with an average diameter of 50 nm were obtained by employing the acidic poly(ether-ester) showing less microphase segregation, while a scaffold structure with a homogeneous and highly interconnected porosity and an average pore size of approximately 15 µm for tissue engineering was prepared using the more hydrophobic copolymer not possessing functional groups. Compression mechanical measurements carried out on the scaffold showed that the more hydrophobic copolymer was suitable for tissue engineering applications. In order to obtain polymers employable both in drug delivery and in tissue engineering a series of block poly(ether-ester)s showing various phase segregations were synthesized by varying the hydrophobic/hydrophilic segment ratio. Copyright © 2010 Society of Chemical Industry

Stimuli‐Responsive Thin Coatings Using Elastin‐Like Polymers for Biomedical Applications

AbstractSmart thin coatings using a recombinant elastin‐like polymer (ELP) containing the cell attachment sequence arginine–glycine–(aspartic acid) (RGD) are fabricated for the first time through simple deposition of the ELP dissolved in aqueous‐based solutions. The biopolymer is produced and characterized using electrophoresis and mass spectroscopy. The temperature and pH responsiveness are assessed by aggregate size measurements and differential scanning calorimetry. The deposition of the studied ELP onto chitosan is followed in situ with a quartz‐crystal microbalance with dissipation monitoring (QCM‐D). Contact angle measurements are performed at room temperature and at 50 °C, showing reversible changes from a moderate hydrophobic behavior to an extremely wettable surface. AFM analysis performed at room temperature reveals a smooth surface and no organized structure. At 50 °C, the surface presents spherical nanometer‐sized structures of collapsed biopolymer chains. Such results suggest that the ELP chains, when collapsed, aggregate into micelle‐like structures at the surface of the substrate, increasing its water affinity. Cell adhesion tests on the developed coatings are conducted using a SaOS‐2 cell line. Enhanced cell adhesion could be observed in the H‐RGD6‐coated surfaces, as compared with the original chitosan monolayer. An intermediate behavior is found in chitosan coated with the corresponding ELP without the RGD sequence. Therefore, the developed films have great potential as biomimetic coatings of biomaterials for different biomedical applications, including tissue engineering and controlled delivery of bioactive agents. Their thermo‐responsive behavior can also be exploited for tunable cell adhesion and controlled protein adsorption.

Responsive Coatings: Stimuli‐Responsive Thin Coatings Using Elastin‐Like Polymers for Biomedical Applications (Adv. Funct. Mater. 20/2009)

Responsive Coatings: Stimuli‐Responsive Thin Coatings Using Elastin‐Like Polymers for Biomedical Applications (Adv. Funct. Mater. 20/2009)