Flexible material formulations for 3D printing of ordered porous beds with applications in bioprocess engineering.

BACKGROUND: 3D printing is revolutioning many industrial sectors and has the potential to enhance also the biotechnology and bioprocessing fields. Here, we propose a new flexible material formulation to 3D print support matrices with complex, perfectly ordered morphology and with tuneable properties to suit a range of applications in bioprocess engineering. FINDINGS: Supports were fabricated using functional monomers as the key ingredients, enabling matrices with bespoke chemistry, such as charged groups, chemical moieties for further functionalization, and hydrophobic/hydrophilic groups. Other ingredients, e.g. crosslinkers and porogens, can be employed to fabricate supports with diverse characteristics of their porous network, providing an opportunity to further regulate the mechanical and mass transfer properties of the supports. Through this approach, we fabricated and demonstrated the operation of Schoen gyroid columns with (I) positive and negative charges for ion exchange chromatography, (II) enzyme bioreactors with immobilized trypsin to catalyse hydrolysis, and (III) bacterial biofilm bioreactors for fuel desulphurization. CONCLUSIONS: This study demonstrates a simple, cost-effective, and flexible fabrication of customized 3D printed supports for different biotechnology and bioengineering applications.

Periodontal Disease and Tooth Wear in a Sample of German Soldiers with Posttraumatic Stress Disorder.

PURPOSE: Dental symptoms of post-traumatic stress disorder (PTSD) patients include a majority of painful temporomandibular joint and masticatory muscle findings, restricted mouth opening, and pronounced attritions. Traumatic occlusal force resulting in injury of the teeth and/or the periodontal attachment apparatus may exceed the adaptive capacity of the individual person or site. This observational cross-sectional study in soldiers with PTSD and a non-PTSD control group after military deployments aimed to evaluate a possible relationship between bruxism and periodontal diagnosis. MATERIALS AND METHODS: Ninety-six in-patients and 27 out-patients (21 women, 102 men) with specialist-confirmed PTSD and bruxism after up to 17 foreign assignments, and 36 male non-PTSD controls with up to 15 foreign assignments underwent general dental, functional, and periodontal examinations. RESULTS: All three groups showed no statistically significant differences in terms of age (34.8 ± 8.6 years), number of teeth (n: 26.3 ± 3.4), status of dentition (DMFT 9.7 ± 6.6), incidence of periodontitis (36%) and recessions (n: 5.8 ± 5.7). From the control group to the out-patient group to the in-patient group, the proportion of smokers and tobacco use increased statistically significantly, as did the extent of attrition. In the in-patient group, with statistically significantly lower educational levels, the number of perceived prophylaxis sessions was statistically significantly reduced in the last two years. CONCLUSIONS: Taking into account the retrospective recording of the last traumatic event, the average time of five years until therapy does not seem to have any consequences for the frequency and severity of inflammatory periodontal disease, recession, and wedge-shaped defects in soldiers with bruxism in PTSD, regardless of the need for in-patient or out-patient treatment.

Experimental investigation and mass transfer modelling of 3D printed monolithic cation exchangers.

3D printing has recently found application in chromatography as a means to create ordered stationary phases with improved separation efficiency. Currently, 3D printed stationary phases are limited by the lack of 3D printing materials suitable for chromatographic applications, and require a strict compromise in terms of desired resolution, model size and the associated print time. Modelling of mass transfer in 3D printed monoliths is also fundamental to understand and further optimise separation performance of 3D printed stationary phases. In this work, a novel 3D printing material was formulated and employed to fabricate monolithic cation exchangers (CEXs) with carboxyl functionalities. CEXs were printed with ligand densities of 0.7, 1.4, 2.1 and 2.8 mmol/g and used in batch adsorption experiments with lysozyme as model protein. All CEXs demonstrated high binding strength towards lysozyme, with maximum binding capacities of up to 108 mg/mL. The experimental results were described using mass transfer models based on lumped pore diffusion and lumped solid diffusion mechanisms adapted to reflect the complex geometry of the 3D printed monoliths. An exact 3D model as well as less computationally demanding 1D and 2D approximations were evaluated in terms of their quality to capture the experimental trend of batch adsorption kinetic data. Overall, the model results indicate that mass transfer in the fabricated CEXs is mostly controlled by pore diffusion at high protein concentrations in the mobile phase, with solid diffusion becoming important at low protein concentrations. Also, the kinetic data were approximated equally well by both the full 3D model as well as the 2D approximation, indicating leaner mathematical models of lower dimensionality can be employed to describe mass transfer in complex three dimensional geometries. We believe this work will help spur the development of 3D printable materials for separations and aid in the development of quantitative platforms to evaluate and optimise the performance of 3D printed monoliths.

Dental Anxiety and Higher Sensory Processing Sensitivity in a Sample of German Soldiers with Inflammatory Periodontal Disease.

(1) Background: Dental anxiety with disease value usually leads to avoidance of dental treatment. For the initial diagnosis of the level of anxiety, questionnaires such as the Hierarchical Anxiety Questionnaire (HAQ) are suitable. The construct of sensory processing sensitivity (SPS) describes a general trait in which people with a higher degree of SPS perceive information more strongly and process it more thoroughly. (2) Methods: This cross-sectional study evaluated the relationship between dental anxiety and higher levels of SPS in 116 soldiers referred with different stages of periodontitis for mandatory dental fitness before military deployment. (3) Results: The proportion of patients with periodontitis in stage III + IV was 39% and in stage I + II was 27%. The mean cumulative values of the questionnaires were 20.9 ± 10.6 for HAQ and 27.7 ± 16.0 for SPS. Eleven moderately anxious patients had a SPS value of 37.4 ± 13.5 and 10 highly anxious patients had a value of 36.3 ± 14.1. Patients diagnosed with stage III + IV periodontitis showed significantly higher values on the SPS subscale Low Sensory Threshold (LST), which describes overstimulation by external sensory stimuli, compared to patients with stage I + II periodontitis. Dental anxiety showed moderately significant correlations with the SPS subscale Ease of Excitation (EOE), which measures emotional reactivity to physiological stimuli. (4) Conclusions: Due to the frequency of dental anxiety and higher sensitivity in patients with severe periodontitis, it is useful to record said frequency.

Demonstration of protein capture and separation using three-dimensional printed anion exchange monoliths fabricated in one-step.

Three-dimensional printing applications in separation science are currently limited by the lack of materials compatible with chromatographic operations and three-dimensional printing technologies. In this work, we propose a new material for Digital Light Processing printing to fabricate functional ion exchange monoliths in a single step. Through copolymerization of the bifunctional monomer [2-(acryloyloxy)ethyl] trimethylammonium chloride, monolithic structures with quaternary amine ligands were fabricated. The novel formulation was optimized in terms of protein binding and recovery, microporous structure, and its swelling susceptibility by increasing its cross-link density and employing cyclohexanol and dodecanol as pore forming agents. In static conditions, the material demonstrated a maximum binding capacity of 104.2 ± 10.6 mg/mL for bovine serum albumin, in line with commercially available materials. Its anion exchange behavior was validated by separating bovine serum albumin and myoglobin on a monolithic bed with Schoen gyroid morphology. The same column geometry was tested for the purification of C-phycocyanin from clarified as well as cell-laden Arthrospira platensis feedstocks. This represents the first demonstration of one-step printed stationary phases to capture proteins directly from solid-laden feedstocks. We believe that the material presented here represents a significant improvement towards implementation of three-dimensional printed chromatography media in the field of separation science.

Direct 3D printing of monolithic ion exchange adsorbers.

Monolithic adsorbers with anion exchange (AEX) properties have been 3D printed in an easy one-step process, i.e. not requiring post-functionalization to introduce the AEX ligands. The adsorber, 3D printed using a commercial digital light processing (DLP) printer, was obtained by copolymerisation of a bifunctional monomer bearing a positively charged quaternary amine as well as an acrylate group, with the biocompatible crosslinker polyethylene glycol diacrylate (PEGDA). To increase the surface area, polyethylene glycol was introduced into the material formulation as pore forming agent. The influence of photoinitiator (Omnirad 819) and photoabsorber (Reactive Orange 16, RO16) concentration was investigated in order to optimize printing resolution, allowing to reliably 3D print features as small as 200 µm and of highly complex Schoen Gyroids. Protein binding was measured on AEX adsorbers with a range of ligand densities (0.00, 2.03, 2.60 and 3.18 mmol/mL) using bovine serum albumin (BSA) and c-phycocyanin (CPC) as model proteins. The highest equilibrium binding capacity was found for the material presenting the lowest ligand density analysed (2.03 mmol/mL), adsorbing 73.7 ± 5.9 mg/mL and 38.0 ± 2.2 mg/mL of BSA and CPC, respectively. This novel 3D printed material displayed binding capacities in par or even higher than commercially available chromatographic resins. We expect that the herein presented approach of using bifunctional monomers, bearing commonly used chromatography ligands, will help overcome the material limitations currently refraining 3D printing applications in separation sciences.