Polymers in 3D printing of external maxillofacial prostheses and in their retention systems.

Maxillofacial defects, arising from trauma, oncological disease or congenital abnormalities, detrimentally affect daily life. Prosthetic repair offers the aesthetic and functional reconstruction with the help of materials mimicking natural tissues. 3D polymer printing enables the design of patient-specific prostheses with high structural complexity, as well as rapid and low-cost fabrication on-demand. However, 3D printing for prosthetics is still in the early stage of development and faces various challenges for widespread use. This is because the most suitable polymers for maxillofacial restoration are soft materials that do not have the required printability, mechanical strength of the printed parts, as well as functionality. This review focuses on the challenges and opportunities of 3D printing techniques for production of polymer maxillofacial prostheses using computer-aided design and modeling software. Review discusses the widely used polymers, as well as their blends and composites, which meet the most important assessment criteria, such as the physicochemical, biological, aesthetic properties and processability in 3D printing. In addition, strategies for improving the polymer properties, such as their printability, mechanical strength, and their ability to print multimaterial and architectural structures are highlighted. The current state of the prosthetic retention system is presented with a focus on actively used polymer adhesives and the recently implemented prosthesis-supporting osseointegrated implants, with an emphasis on their creation from 3D-printed polymers. The successful prosthetics is discussed in terms of the specificity of polymer materials at the restoration site. The approaches and technological prospects are also explored through the examples of the nasal, auricle and ocular prostheses, ranging from prototypes to end-use products.

Fabrication of moldable chitosan gels via thermally induced phase separation in aqueous alcohol solutions.

Wide application of chitosan in modern technologies is limited by the lack of reliable and low-cost techniques to prepare size-tuned constructs with a complex surface morphology, improved optical and mechanical properties. We report a new simple method for preparation of transparent thermoreversible chitosan alcogels from chitosan/H2O/ethanol ternary systems. This method, termed "low temperature thermally induced phase separation under non-freezing conditions" (LT-TIPS-NF), fine tunes gelation by adjusting only temperature (from 5 to -25 °C) and varying the initial content of chitosan (from 0.5 to 2.0 wt%) and ethanol (from 28.5 to 47.5 vol%). Transparent non-swelling final constructs of complex shape are prepared by fixing the pre-formed alcogels with a base solution. The size of the gel constructs is limited only by the dimensions of the mold and the cooling chamber. The LT-TIPS-NF is applicable both in injection molding and 3D printing techniques. The in vitro and in vivo experiments show the absence of prominent cytotoxicity and well-defined cell adhesion on the obtained hydrogels. Thus, this facile and scalable technique provides the multifunctional chitosan gel preparation with easily controlled properties exploiting inexpensive, renewable, and environmentally friendly source polysaccharide. These materials have prospects for a variety of uses, especially for biomedical applications.

Fluoroplast-polyaniline-coated adsorbent for one-step isolation of DNA for PCR detection of viral hepatitides (HBV and TTV).

AIMS: To demonstrate the effectiveness of application of the adsorbent successively modified with nano-layers of fluoroplast and polyaniline for one-step isolation of DNA of hepatitis B virus and transfusion-transmitted virus from human serum. MATERIALS & METHODS: The technique is based on the application of the spin-cartridges containing porous adsorbent for one-step viral DNA isolation from serum followed by polymerase chain reaction. RESULTS: The developed adsorbent was shown to be effective for one-step isolation of viral DNA from serum samples for polymerase chain reaction diagnostics. CONCLUSION: The effectiveness of the developed adsorbent application for isolation of viral DNA from serum for polymerase chain reaction diagnostics was confirmed in comparison with standard methods. Thus, the facile sample preparation method of viral DNA isolation was elaborated.

Novel composite matrices modified with nanolayers of polymers as perspective materials for separation of biomolecules and bioanalysis.

AIMS: A new approach for the preparation of adsorbents for one-step isolation/purification of DNA from different samples (e.g., bacterial lysates, smears and blood) has been developed. MATERIALS & METHODS: The technique is based on the use of porous silica preliminary treated with ozone followed by grafting of polymer nanolayers on the activated carrier surface. The chemical nature of active centers, their stability and conditions for the use of the activated support as heterogeneous initiator of different macromolecular reactions were studied. RESULTS: The adsorbents modified with thin (~3.0-7.5 nm) polytetrafluoroethylene and polyaniline layers were prepared and characterized. Sorption properties of the obtained adsorbents were demonstrated on examples of express (2-5 min) one-step DNA isolation for direct use in PCR diagnostics. CONCLUSION: The effectiveness of the developed adsorbents used for DNA isolation and purification was confirmed in comparison with the standard methods. Thus, a facile (alternative in relation to irradiation postpolymerization or standard oxidative polymerization techniques) manufacturing method of the materials for nucleic acids sample preparation was developed.