Establishment of suitable parameters for laser machining based production of polymeric implants

Laser material processing enables precise machining of a wide variety of materials. In order to prevent an excessive heat input, which leads to irreversible material damage, the process parameters have to be adapted to the processed material. To keep the heat load as low as possible, the potential of femtosecond laser technology is exploited. The processing of semi-finished products using femtosecond laser technology is highly depending on the processed material. In this regard, we established a workflow and basic parameters for the processing of polymeric material. The performed parameter study varying cutting speed, cutting gas pressure and pulse energy to optimize the manufacturing process. Scanning electron microscopy (SEM) was utilized to analyze the cutting results, such as cut edge quality or possible melted areas. The established parameter set is also suitable for processing of very filigree material structures as used in innovative medical devices. The SEM analysis of the established parameter set showed that a homogeneous, nonwavy cut edge was created along the kerf.

Influence of sterilization conditions on sulfate-functionalized polyGGE

Sulfated biomolecules are known to influence numerous biological processes in all living organisms. Particularly, they contribute to prevent and inhibit the hypercoagulation condition. The failure of polymeric implants and blood contacting devices is often related to hypercoagulation and microbial contamination. Here, bioactive sulfated biomacromolecules are mimicked by sulfation of poly(glycerol glycidyl ether) (polyGGE) films. Autoclaving, gamma-ray irradiation and ethylene oxide (EtO) gas sterilization techniques were applied to functionalized materials. The sulfate group density and hydrophilicity of sulfated polymers were decreased while chain mobility and thermal degradation were enhanced post autoclaving when compared to those after EtO sterilization. These results suggest that a quality control after sterilization is mandatory to ensure the amount and functionality of functionalized groups are retained.

Aspirin-Loaded Polymeric Films for Drug Delivery Systems: Comparison between Soaking and Supercritical CO2 Impregnation

Polymeric implants loaded with drugs can overcome the disadvantages of oral or injection drug administration and deliver the drug locally. Several methods can load drugs into polymers. Herein, soaking and supercritical CO2 (scCO2) impregnation methods were employed to load aspirin into poly(l-lactic acid) (PLLA) and linear low-density polyethylene (LLDPE). Higher drug loadings (DL) were achieved with scCO2 impregnation compared to soaking and in a shorter time (3.4 ± 0.8 vs. 1.3 ± 0.4% for PLLA; and 0.4 ± 0.5 vs. 0.6 ± 0.5% for LLDPE), due to the higher swelling capacity of CO2. The higher affinity of aspirin explained the higher DL in PLLA than in LLDPE. Residual solvent was detected in LLDPE prepared by soaking, but within the FDA concentration limits. The solvents used in both methods acted as plasticizers and increased PLLA crystallinity. PLLA impregnated with aspirin exhibited faster hydrolysis in vitro due to the catalytic effect of aspirin. Finally, PLLA impregnated by soaking showed a burst release because of aspirin crystals on the PLLA surface, and released 100% of aspirin within 60 days, whereas the PLLA prepared with scCO2 released 60% after 74 days by diffusion and PLLA erosion. Hence, the scCO2 impregnation method is adequate for higher aspirin loadings and prolonged drug release.

Tunable Boc Modification of Lignin and Its Impact on Microbial Degradation Rate

<p>A new type of modified lignin, lignin-p-Boc, was obtained through reaction with di-<i>tert</i>-butyl dicarbonate (Boc₂O) in aqueous media catalyzed by 4-dimethylaminopyridine (DMAP). Boc modification occurred regardless of type of lignin, was tunable, and proceeded well in recovering lignin at high purity from sodium lignosulfonate (a common byproduct from pulping industry; lignin content: 60%). Lignin-p-BOC was demonstrated as a potential reactive filler in green plastic and as a potential crosslinker in design of bioresorbable composite polymeric implants. Furthermore, the effects of the modification on the breakdown rate of alkali lignin by microbes was investigated, and the results showed that the modification substantially decreases the breakdown rate. The tunable Boc modification process was designed via a system thinking, including availability of raw lignin, economical/green modification, potentiality of drop-in-change to current thermoplastic processing, modification impact on microbial degradability/disposed environment at the end of use life; hence the holistic consideration makes this alternative method for upgrade of technical lignins very practical for future industrial application. Via forming “easily breakable covalent bonds” with thermopolymers, Lignin-p-BOCs are also promising to play an important role as both excellent binders via “random match” and reductants in transforming linear plastic waste into circular plastics.</p><br>

A critical review on ultra high molecular weight polyethylene (UHMWPE) for prosthesis and implant functions

Polymer composites benefit joint prostheses and implants in biomaterials due to their high strength, reliability, and elasticity modules. The addition of nanoparticles into the polymer-based matrix has effectively demonstrated up-grading wear resistance and implant strength improvement. Therefore, due to the elevated surface area and immense properties, considerable attention has been paid to research in integrating nanoparticles for a wide variety of functions. The UHMWPE is extensively used to develop prosthesis and orthopedic operations due to exceptional mechanical and biocompatible features. The various research studies revealed the fabrication of bio nanocomposites with the polymer matrix possesses superior biocompatibility and durability. This paper presents a critical review of UHMWPE for the latest advancement in polymeric implants by adding different nanoparticles. Another exciting aspect of the proposed work is the addition of different organic (carbon, polymeric) and inorganic (metallic and metal oxides) nanoparticles to develop bio-nano composites. An effort has been made to highlight the exceptional features of modified UHMWPE by supplementing nanofillers for biomedical functions.

Manufacturing Techniques: Polymer Implants as Drug Delivery Systems for Cancer Therapy

The manufacturing processes of polymeric implants for controlled drug release suggest a promising perspective of use for chemotherapeutic treatments. The objective of this study was to carry out a bibliographical survey of the last 10 years with experimental works to draw up a profile of methodologies and results achieved in this area. The literature search revealed 739 references, of which 19 were selected. The manufacturing by extrusion and injection are the most used. Regarding geographical distribution, Brazil occupies the 2nd place in the general list. The analysis of the literature on controlled release techniques of chemotherapeutic drugs demonstrates the scarce production in this area. It would be of great interest to have more studies on this topic, since it would be an alternative in the chemotherapeutic treatment.

Nonthermal plasma treatment of polymers modulates biological fouling but can cause material embrittlement

Plasma-based treatment is a prevalent strategy to alter biological response and enhance biomaterial coating quality at the surfaces of biomedical devices and implants, especially polymeric materials. Plasma, an ionized gas, is often thought to have negligible effects on the bulk properties of prosthetic substrates given that it alters the surface chemistry on only the outermost few nanometers of material. However, no studies to date have systematically explored the effects of plasma exposure on both the surface and bulk properties of a biomaterial. This work examines the time-dependent effects of a nonthermal plasma on the surface and bulk properties of polymeric implants, specifically polypropylene surgical meshes and sutures. Findings suggest that plasma exposure improved resistance to fibrinogen adsorption and Escherichia coli attachment, and promoted mammalian fibroblast attachment, although increased duration of exposure resulted in a state of diminishing returns. At the same time, it was observed that plasma exposure can be detrimental to the material properties of individual filaments (i.e. sutures), as well as the structural characteristics of knitted meshes, with longer exposures resulting in further embrittlement and larger changes in anisotropic qualities. Though there are few guidelines regarding appropriate mechanical properties of surgical textiles, the results from this investigation imply that there are ultimate exposure limits for plasma-based treatments of polymeric implant materials when structural properties must be preserved, and that the effects of a plasma on a given biomaterial should be examined carefully before translation to a clinical scenario.