Correction: 3D printed and stimulus responsive drug delivery systems based on synthetic polyelectrolyte hydrogels manufactured via digital light processing

Correction for '3D printed and stimulus responsive drug delivery systems based on synthetic polyelectrolyte hydrogels manufactured via digital light processing' by Sonja Vaupel et al., J. Mater. Chem. B, 2023, DOI: https://doi.org/10.1039/d3tb00285c.

3D printed and stimulus responsive drug delivery systems based on synthetic polyelectrolyte hydrogels manufactured via digital light processing

Hydrogels are three-dimensional hydrophilic polymeric networks absorbing up to and even more than 90 wt% of water. These superabsorbent polymers retain their shape during the swelling process while enlarging their volume and mass. In addition to their swelling behavior, hydrogels can possess other interesting properties, such as biocompatibility, good rheological behavior, or even antimicrobial activity. This versatility qualifies hydrogels for many medical applications, especially drug delivery systems. As recently shown, polyelectrolyte-based hydrogels offer beneficial properties for long-term and stimulus-responsive applications. However, the fabrication of complex structures and shapes can be difficult to achieve with common polymerization methods. This obstacle can be overcome by the use of additive manufacturing. 3D printing technology is gaining more and more attention as a method of producing materials for biomedical applications and medical devices. Photopolymerizing 3D printing methods offer superior resolution and high control of the photopolymerization process, allowing the fabrication of complex and customizable designs while being less wasteful. In this work, novel synthetic hydrogels, consisting of [2-(acryloyloxy) ethyl]trimethylammonium chloride (AETMA) as an electrolyte monomer and poly(ethylene glycol)-diacrylate (PEGDA) as a crosslinker, 3D printed via Digital Light Processing (DLP) using a layer height of 100 μm, are reported. The hydrogels obtained showed a high swelling degree q∞m,t ∼ 12 (24 h in PBS; pH 7; 37 °C) and adjustable mechanical properties with high stretchability (ε_max ∼ 300%). Additionally, we embedded the model drug acetylsalicylic acid (ASA) and investigated its stimulus-responsive drug release behaviour in different release media. The stimulus responsiveness of the hydrogels is mirrored in their release behavior and could be exploited in triggered as well as sequential release studies, demonstrating a clear ion exchange behavior. The received 3D-printed drug depots could also be printed in complex hollow geometry, exemplarily demonstrated via an individualized frontal neo-ostium implant prototype. Consequently, a drug-releasing, flexible, and swellable material was obtained, combining the best of both worlds: the properties of hydrogels and the ability to print complex shapes.

Micro Injection Molding of Drug-Loaded Round Window Niche Implants for an Animal Model Using 3D-Printed Molds

A novel approach for the long-term medical treatment of the inner ear is the diffusion of drugs through the round window membrane from a patient-individualized, drug-eluting implant, which is inserted in the middle ear. In this study, drug-loaded (10 wt% Dexamethasone) guinea pig round window niche implants (GP-RNIs, ~1.30 mm × 0.95 mm × 0.60 mm) were manufactured with high precision via micro injection molding (µIM, T_mold = 160 °C, crosslinking time of 120 s). Each implant has a handle (~3.00 mm × 1.00 mm × 0.30 mm) that can be used to hold the implant. A medical-grade silicone elastomer was used as implant material. Molds for µIM were 3D printed from a commercially available resin (T_G = 84 °C) via a high-resolution DLP process (xy resolution of 32 µm, z resolution of 10 µm, 3D printing time of about 6 h). Drug release, biocompatibility, and bioefficacy of the GP-RNIs were investigated in vitro. GP-RNIs could be successfully produced. The wear of the molds due to thermal stress was observed. However, the molds are suitable for single use in the µIM process. About 10% of the drug load (8.2 ± 0.6 µg) was released after 6 weeks (medium: isotonic saline). The implants showed high biocompatibility over 28 days (lowest cell viability ~80%). Moreover, we found anti-inflammatory effects over 28 days in a TNF-α-reduction test. These results are promising for the development of long-term drug-releasing implants for human inner ear therapy.

Influence of the Volatility of Solvent on the Reproducibility of Droplet Formation in Pharmaceutical Inkjet Printing

Drop-on-demand (DOD) inkjet printing enables exact dispensing and positioning of single droplets in the picoliter range. In this study, we investigate the long-term reproducibility of droplet formation of piezoelectric inkjet printed drug solutions using solvents with different volatilities. We found inkjet printability of EtOH/ASA drug solutions is limited, as there is a rapid forming of drug deposits on the nozzle of the printhead because of fast solvent evaporation. Droplet formation of c = 100 g/L EtOH/ASA solution was affected after only a few seconds by little drug deposits, whereas for c = 10 g/L EtOH/ASA solution, a negative affection was observed only after t = 15 min, while prominent drug deposits form at the printhead tip. Due to the creeping effect, the crystallizing structures of ASA spread around the nozzle but do not clog it necessarily. When there is a negative affection, the droplet trajectory is affected the most, while the droplet volume and droplet velocity are influenced less. In contrast, no formation of drug deposits could be observed for highly concentrated, low volatile DMSO-based drug solution of c = 100 g/L even after a dispensing time of t = 30 min. Therefore, low volatile solvents are preferable to highly volatile solvents to ensure a reproducible droplet formation in long-term inkjet printing of highly concentrated drug solutions. Highly volatile solvents require relatively low drug concentrations and frequent printhead cleaning. The findings of this study are especially relevant when high droplet positioning precision is desired, e.g., drug loading of microreservoirs or drug-coating of microneedle devices.

Volumetric mass density measurements of mesenchymal stem cells in suspension using a density meter

To use regeneratively active cells for cell therapeutic applications, the cells must be isolated from their resident tissues. Different isolation procedures subject these cells to varying degrees of mechanical strain, which can affect the yield of cell number and viability. Knowledge of cell volumetric mass density is important for experimental and numerical optimization of these procedures. Although methods for measuring cell volumetric mass density already exist, they either consume much time and cell material or require a special setup. Therefore, we developed a user-friendly method that is based on the use of readily available instrumentation. The newly developed method is predicated on the linear relationship between the volumetric mass density of the cell suspension and the volumetric mass density, number, and diameter of the cells in the suspension. We used this method to determine the volumetric mass density of mesenchymal stem cells (MSCs) and compared it to results from the established density centrifugation.

Digital Light Processing of Round Window Niche Implant Prototypes for Implantation Studies

A new approach that offers the potential for local drug delivery to the inner ear is a 3D printed, patient individualized, drug-loaded implant that precisely fits into the round window niche (RWN). Anatomically correct digital light processing (DLP) 3D printed implant prototypes are beneficial for preoperative planning and rehearsal of implantation techniques due to tactile feedback. The aim is to define desired mechanical material properties for future RWN implants. For this purpose, RWN implant prototypes (RWN-IPs) were DLP 3D printed using commercially available E-Shell 500 and E-Shell 600 materials (Envisiontec GmbH, Gladbeck, Germany) and a selfestablished PEGDA700 composition. These photopolymers are suitable for 3D printing RWN-IPs that feature different mechanical characteristics. The (1) mechanical properties (tensile test) were investigated, (2) the implantation feasibility and (3) fitting accuracy in human cadaver RWN were evaluated. As a result, E-Shell 500 has relatively high stretchability (ɛm ~ 60%) while E-Shell 600 and PEGDA700 are brittle and PEGDA700 has low strength. The E-Shell 500 material performs by far the best at handling and insertion. EShell 600 has adequate strength but is hard to handle because of rigid material behavior. PEGDA700 enables high 3D printing accuracy but lacks adequate mechanical behavior for adequate insertion of implant prototypes in RWN.

Micro injection molding of individualised implants using 3D printed molds manufactured via digital light processing

Here, we demonstrate a manufacturing process for individualised, small-sized implant prototypes. Our process is promising for the manufacturing of drug-releasing (micro)implants to be implanted in the round window niche (RWN-I, solid body, free-form-shaped design, 1.1 x 2.7 x 3.1 mm) and for frontal neo-ostium implants (FO-I, tube-like design, length ~ 7 mm, Ø ~ 2-6 mm) for frontal sinus drainage. Implant prototypes are manufactured using micro injection molding (μIM). We use digital light processing (DLP) as a 3D printing technique for rapid tooling of accurate molds for the μIM process. A common acrylate-based photopolymer for stiff and high-detailed modelling but with low head deflection temperature of HDT = 60.5 °C is used for DLP 3D printing of the molds. The molds were 3D printed with a layer height of 50 μm in about 20 min (RWN-I) and 60 min (FO-I). For μIM investigations, we use liquid silicone rubber (LSR) as a biocompatible and medically relevant material. Micro injection molding of LSR was investigated using mold temperatures between Tmold = 110 °C (long tcuring ~ 2 h) up to Tmold = 160 °C (short tcuring ~ 5 min). As a result, small-sized, complex-shaped implant prototypes of LSR can be successfully manufactured via μIM using high Tmold = 160 °C and short curing time. DLP 3D printing material with relative low HDT = 60.5 °C was suitable for μIM. There is no significant wear of the molds, when used for a low number of μIM cycles (n ~ 8). Design of metal mold housing has to be suitable (perfect fit of mold, no cavities facing the molds surface for prevention of thermal expansion of mold into cavities).

Customised micro-electrode array (MEA) test setup featuring a silicone-casted overlay with two chambers for separated cell seedings

Micro-electrode array (MEA) systems are noninvasive platforms for the investigation of electrophysiological properties of cell layers, such as spontaneously active cardiomyocytes. An MEA chip is composed of two-dimensional grids of dot-like electrodes embedded into glass. Here we present a test setup featuring a customised two-chamber silicone overlay. The overlay is designed to be placed on an MEA with two separate electrode fields and enables the seeding of two distinct cell sub-types on the MEA for synchronised drug testing applications while giving the possibility of analysing intersubtype-specific cellular interactions. The overlay has a full size of 10 x 10 x 5 mm (width x length x height), each chamber has a size of 2.5 x 6 x 5 mm (V = 75 mm³). The chambers are separated by a wall with a thickness of 0.3 mm. The overlay was manufactured via silicone-casting, utilising a 3D printed model. The model is 3D printed via high accurate digital light processing (DLP). In addition, a DLP 3D printed cover optimises the attachment of the overlay on an MEA. A proofof- principle of the utilisation of the overlay is demonstrated.

In vitro release of chlorhexidine from UV-cured PEGDA drug delivery scaffolds

Drug delivery systems (DDS) are suitable for controlled local drug release in order to ensure safety and effectiveness of medical treatment. The choice and characterization of biomaterials that can be used as a DDS is a challenging step in the administration of drugs. Novel 3D printing photopolymerization-based techniques create the possibility for designing individual, patient-tailored DDS. Poly(ethylene glycol) diacrylate`s (PEGDA`s) chemical and biological properties make it a suitable photopolymerisable resin for the creation of DDS. This study describes the in vitro release of the antiseptic drug chlorhexidine (CHX) from UV-cured PEGDA and its copolymers (butanediol diacrylate, pentaerythritol triacrylate and pentaerythritol tetraacrylate) samples. A substantial decrease in CHX release with increasing concentration of the copolymers in comparison to pure PEGDA was obtained only for butanediol diacrylate. For pentaerythritol triacrylate and pentaerythritol tetraacrylate only a tendency of decreased CHX release with increasing concentration was detected. Therefore, release profiles of the low molecular drug CHX from PEGDA samples could be modified by the addition of copolymers with a different number of acrylate groups and PEGDA can be considered as a promising candidate for the preparation of novel DDS.

Initial study on removing cellular residues from hydrostatic high-pressure treated allogeneic tissue using ultrasound

Hydrostatic high-pressure technology (HHD) devitalizes tissue quickly and gently, without negatively affecting the structural properties. HHD-treated tissues must be cleaned from devitalized cells. A partially automated, gentle, reproducible and timesaving rinsing test setup utilizing ultrasound is demonstrated in this study. The test setup is used to clean HHD-treated bone allografts of tissue residues and prevent microbiological contamination. A rinsing procedure is investigated. Residual DNA content determination is utilized to analyze cleaned bone allograft tissue for rinsing procedure evaluation.

Printing of vessels for small functional tissues – a preliminary study

Vascularization of bioprinted constructs to ensure sufficient nutrient supply still remains to be a significant task in the tissue engineering community. In order to mimic functional tissue, it is necessary to be able to print vessels in various size scales, which places particularly high demands on the 3D printing technology and materials. In this preliminary study, we focused on the production of small hollow structures for the application in small functional units of living tissue. To fabricate hollow structures, the freeform reversible embedding of suspended hydrogels (FRESH) - method was utilized (Hinton et al.). A sodium alginate solution (5 % w/v) was used as a bioink. The scaffolds were fabricated with the Allevi 1 (Allevi Inc., PA, USA), a pneumatic extrusion-based bioprinter and plotted into a gelatine slurry serving as fugitive support. For first cell experiments, the bioink was loaded with immortalized mouse HL1-cells. A proof of concept could be shown since we were able to reliably create vessel-like structures with an inside diameter of 1.2 to 1.6 mm, a length of up to 8 mm and a wall thickness of 0.4 to 0.6 mm. In this study, the geometric requirements to print hollow structures for small functional tissues could be achieved. To expand the field of applications the resolution of the printing process has to be further improved. Moreover, the cell density should be increased to reach physiological cell numbers and extended with endothelial cells.

PEGDA drug delivery scaffolds prepared with UV curing process

Individually tailored drug delivery systems (DDSs) are considered one of the most promising therapeutic tools for the creation of safe and effective treatments. DDSs as a novel approach should be beneficial in curing systemic as well as local ailments, where a high topical concentration of the drug and a reduction of side effects are desirable. It could also be favorable for patients requiring customized treatments, showing atypical profiles of drug metabolism. Development of particular drug delivery devices require the selection of a suitable scaffold material, which should exhibit proper mechanical and biological properties, but also enable adjustment of the drug release according to a specific need. Thus, it is extremely important to expand the knowledge concerning potential DDS components. Poly(ethylene glycol) diacrylate (PEGDA) according to its properties can be easily used as a DDS resin and shaped into a desired structure with the employment of techniques based on photopolymerization, including some novel 3D printing techniques. As a continuation of our previous works, in this paper drug release studies from conventionally prepared PEGDA scaffolds are presented. We have shown that in PEGDA materials, the release profile of the low molecular weight model drug acetylsalicylic acid can be altered by water content. PEGDA as a delivery material should be further investigated to specify its potential as a comonomer and a matrix for pharmaceutical agents.

Biocompatibility and thermodynamic properties of PEGDA and two of its copolymer

During the last years substantial effort was taken in order to provide an effective and safe pharmacotherapy that can be adjusted to the individual needs of patients. Stereolithography is a simple and accurate additive manufacturing technology. According to these characteristics, it may offer unique opportunities for the industrial fabrication of structured drug delivery systems (DDS), which can be tailored to individual needs. During the stereolithographic process photopolymerizable biomaterial is transformed, layer by layer, into the designed polymer DDS. Combined with inkjet printing in an innovative 3D building system it enables selective and precise incorporation of the drug depot into the basic body of the DDS. Poly(ethylene glycol) diacrylate (PEGDA), a hydrophilic and low-immunogenic compound, is a suitable material as drug depot in a photopolymerizable basic biomaterial for this purpose. By combination of PEGDA with other acrylates, the physical properties of the DDS can be adjusted towards the desired characteristics. Therefore, it should be possible to modify the drug release profile through the positioning of drug depots and the diffusion of the drug and adjust it for a wide range of applications. In this study we investigated basic biological and thermodynamic properties of conventionally photocured systems consisting of PEGDA and its coacrylates: 1,3-butanediol diacrylate and pentaerythritol triacrylate. Our preliminary outcomes demonstrate the hydrophilic character of the samples and the importance of a rinsing process. They also show that the addition of different amounts of co-monomers influence the glass transition temperature, which increases with increasing content of coacrylate. Therefore, PEGDA/comonomer composition can be used as a tool for the modification of drug release properties. Consequently, these materials may be regarded as interesting and promising components for DDS via novel additive manufacturing with the ability of highly controlled drug release.

A Novel Hybrid Additive Manufacturing Process for Drug Delivery Systems with Locally Incorporated Drug Depots

Here, we present a new hybrid additive manufacturing (AM) process to create drug delivery systems (DDSs) with selectively incorporated drug depots. The matrix of a DDS was generated by stereolithography (SLA), whereas the drug depots were loaded using inkjet printing. The novel AM process combining SLA with inkjet printing was successfully implemented in an existing SLA test setup. In the first studies, poly(ethylene glycol) diacrylate-based specimens with integrated depots were generated. As test liquids, blue and pink ink solutions were used. Furthermore, bovine serum albumin labeled with Coomassie blue dye as a model drug was successfully placed in a depot inside a DDS. The new hybrid AM process makes it possible to place several drugs independently of each other within the matrix. This allows adjustment of the release profiles of the drugs depending on the size as well as the position of the depots in the DDS.

Preliminary Study on 3D printing of PEGDA Hydrogels for Frontal Sinus Implants using Digital Light Processing (DLP)

Digital Light Processing (DLP) enables high precision 3D-printing of photopolymers and holds promising potential for patient-specific implant solutions. On the material side, Poly(ethylene glycol) diacrylate (PEGDA) has emerged as an interesting material for use in biomedical applications. For adequate photopolymerization, a photoinitiator and a light absorber are necessary, using welldefined concentrations. This study shows preliminary results of DLP 3D-printing of different PEGDA hydrogel compositions with varying water content (90; 70; 50; 30; 10; 0 % w/w) as well as varying concentrations of a photoinitiator and a light absorber. Printing performance and accuracy are investigated by printing rectangular test samples as well as an anatomically customised tubular frontal sinus implant prototype. For basic mechanical characterisation, the hardness of the printed hydrogels is investigated using a Shore A durometer. The results show a decrease in printing accuracy and hardness with an increasing water content of the composition. There is a need to use a light absorber to reach high printing accuracy. This leads to a need for increasing photoinitiator concentration and prolonged light exposure to achieve proper printing performance.

Thermomechanical properties of PEGDA in combination with different photo-curable comonomers

The technology of pharmaceutical drug delivery systems (DDS) as an individual and adjustable tool for drug administration has been intensively developed in the last years. Additive manufacturing (AM) techniques, such as stereolithography, are a promising approach towards DDS scaffold manufacturing. Stereolithography, by using layerby- photo-polymerisation, creates DDS scaffolds with highly controlled 3D geometry. Combined with inkjet printing it allows a very precise positioning of the drug depot in the basic scaffold and therefore also a better control of the drug release. Furthermore, this hybrid AM technique also allows for the creation of a multi-drug DDS with a several drug depots localized in desired positions within the scaffold. Determination of the scaffold and drug depot material properties is one of the initial steps for such novel DDS development. Basic characteristics, such as stiffness, elasticity or glass transition temperature (Tg), are important for designing and adapting the material for biomedical application. The photosensitive poly(ethylene glycol) diacrylate (PEGDA) can be easily formed into a desired biocompatible scaffold geometry via stereolithography. In this study we have focused on the evaluation of PEGDA (Mn=700 g/mol) as a pure and copolymer system in combination with other acrylates (butanediol diacrylate, pentaerythritol triacrylate) as possible materials for DDS using this novel hybrid AM technique. Irgacure 2959, a biocompatible photoinitiator (PI), was used as a radical starter for photopolymerisation. Samples varying in PI and coacrylate concentration were prepared by conventional photopolymerisation. Physico-chemical analyses of the samples were performed and several parameters, such as stiffness, elongation at break and glass transition temperatures, were determined.

Novel 3D printing concept for the fabrication of time-controlled drug delivery systems

Three-dimensional (3D) printing has become a popular technique in many areas. One emerging field is the use of 3D printing for the development of 3D drug delivery systems (DDS) and drug-loaded medical devices. This article describes a novel concept for the fabrication of timecontrolled drug delivery systems based on stereolithography combined with inkjet printing. An inkjet printhead and an UV-LED light source have been integrated into an existing stereolithography system. Inkjet printing is used to selectively incorporate active pharmaceutical ingredients (API) during a stereolithographic 3D printing process. In an initial experimental study, poly (ethylene glycol) diacrylate (PEGDA) was used as polymer whereas 2-Hydroxy-4´-(2- hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) and Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) were used as photoinitiators. Basic structures could be manufactured successfully by the new hybrid 3D printing system.

Thermomechanical properties of PEGDA and its co-polymers

Current research activities focus on personalized, comfortable and safe products for systemic or local drug application in patients. Poly(ethylene glycol) diacrylate is in particular interest as a drug delivery material, as it shows appropriate biological properties such as hydrophilicity and low toxicity. Additionally, as an easily photopolymerizable compound it can be also utilized for the production of scaffolds with the use of different techniques such as stereolithography. Even though it is often used as a biomaterial or as a copolymer in many photopolymer systems for drug delivery, thermomechanical analysis and basic understanding are rare.

Therefore, we investigated the tensile stress and the glass transition temperature of pure PEGDA and of its copolymers with 1,3-butanediol diacrylate or pentaerythritol triacrylate, as a function of the photoinitiator (PI) or acrylate concentration. Additionally, we demonstrated that the washing procedure decreases the tensile stress values. We showed, that by the means of composing PEGDA with these, it is possible to influence thermomechanical properties of the sample. Our outcomes have revealed, that there is no clear influence of the PI concentration on the thermomechanical properties. However there is an influence of the monomer concentration. Therefore, it should be possible to modify drug release profiles in future experiments.

Inkjet printing for localized coating and functionalization of medical devices

Inkjet printing has become essential for pharmaceutical research as well as biomedical applications. It is a promising tool to meet future challenges in patientindividual designed pharmaceuticals and implants. In this context, the main areas of use are high-throughput screening (HTS), drug-loaded microparticles, drug formulation and oral dose development, 3D-printing/bioprinting as well as coating of implants. This study deals with the latter. In view of promising applications for localized coating and functionalization of implant surfaces this work shows preliminary results on inkjet printing of the polymer poly(2- ethyl-2-oxazoline) (PetOx), a protein repellent polymer (PRP). To deposit single droplets with small volumes (~500 pl) of aqueous PetOx solution (50 g/l), printing parameters were determined for the piezo-driven drop-ondemand inkjet printhead NanoTip J, operating in a Nanoplotter 2.1 (both from GeSiM mbH, Germany). Different printing strategies are demonstrated by varying droplet spacing and drying time while printing on hydrophilic glass substrate. Printing and stacking of almost uniform polymer lines (width ~ 200 μm) is demonstrated.

Bioprinting of three dimensional tumor models: a preliminary study using a low cost 3D printer

The deep understanding of cancer and tumor genesis, as well as the development of new therapy strategies still remains one of the emerging challenges in modern medicine. To meet these challenges it seems to be absolutely necessary to overcome the drawbacks of the established 2D in vitro models. Especially the missing microenvironment of the tumor, which means the absence of stroma and immune cells, results in a missing cell-cell and cell-stroma interaction as well as disrupted functional communication pathways. Modern 3D culture systems and 3D printing or rather bioprinting technologies attempt to solve this issue and aim to closely mimic natural tumor microenvironment. In this preliminary work we are going to present the first steps of establishing an artificial 3D tumor model utilising a low cost 3D printer. Therefore the printer had been modified with an open-source syringe pump to become a functional bioprinter using viscosity modulated alginate hydrogel. In the first attempts L929 mouse fibroblasts, which are an integral component of natural stroma, had been incorporated into the hydrogel matrix and printed into scaffolds. Subsequent to the printing process the scaffolds got ionically crosslinked with a 5% w/v aqueous solution of CaCl2 to become mechanically stable. After three days of cultivation viability testing had been performed by utilising FDG staining and PET CT to obtain a volumetric viability measurement. The viability imaging showed vital cells homogeneously distributed in the scaffold and therefore stands as an evidence for a working low cost bioprinting process and a successful first step for the development of an artificial 3D tumor model.

Adjusting inkjet printhead parameters to deposit drugs into micro-sized reservoirs

Drug delivery systems (DDS) ensure that therapeutically effective drug concentrations are delivered locally to the target site. For that reason, it is common to coat implants with a degradable polymer which contains drugs. However, the use of polymers as a drug carrier has been associated with adverse side effects. For that reason, several technologies have been developed to design polymer-free DDS. In literature it has been shown that micro-sized reservoirs can be applied as drug reservoirs. Inkjet techniques are capable of depositing drugs into these reservoirs. In this study, two different geometries of micro-sized reservoirs have been laden with a drug (ASA) using a drop-on-demand inkjet printhead. Correlations between the characteristics of the drug solution, the operating parameters of the printhead and the geometric parameters of the reservoir are shown. It is indicated that wettability of the surface play a key role for drug deposition into micro-sized reservoirs.

Tomographic particle image velocimetry of a water-jet for low volume harvesting of fat tissue for regenerative medicine

Particle Image Velocimetry (PIV) measurements of a water-jet for water-assisted liposuction (WAL) are carried out to investigate the distribution of velocity and therefore momentum and acting force on the human sub-cutaneous fat tissue. These results shall validate CFD simulations and force sensor measurements of the water-jet and support the development of a new WAL device that is able to harvest low volumes of fat tissue for regenerative medicine even gentler than regular WAL devices.

Inkjet printing of viable human dental follicle stem cells

Inkjet printing technology has the potential to be used for seeding of viable cells for tissue engineering approaches. For this reason, a piezoelectrically actuated, drop-on-demand inkjet printing system was applied to deliver viable human dental follicle stem cells (hDFSC) of sizes of about 15 μm up to 20 μm in diameter. The purpose of these investigations was to verify the stability of the printing process and to evaluate cell viability post printing. Using a Nanoplotter 2.1 (Gesim, Germany) equipped with the piezoelectric printhead NanoTip HV (Gesim, Germany), a concentration of 6.6 ×106 cells ml−1 in DMEM with 10% fetal calf serum (FCS) could be dispensed. The piezoelectric printhead has a nominal droplet volume of ~ 400 pl and was set to a voltage of 75 V and a pulse of 50 μs while dosing 50 000 droplets over a time of 100 seconds. The volume and trajectory of the droplet were checked by a stroboscope test right before and after the printing process. It was found that the droplet volume decreases significantly by 35% during printing process, while the trajectory of the droplets remains stable with only an insignificant number of degrees deviation from the vertical line. It is highly probable that some cell sedimentations or agglomerations affect the printing performance. The cell viability post printing was assessed by using the Trypan Blue dye exclusion test. The printing process was found to have no significant influence on cell survival. In conclusion, drop-on-demand inkjet printing can be a potent tool for the seeding of viable cells.

[Factitious recurrent septicemia and gastrointestinal corrosive burns]

HISTORY AND ADMISSION FINDINGS

A 39-year-old woman was admitted for the treatment of recurrent septicemia, corrosive esophageal and gastric mucosal injury, and bloody stools.

INVESTIGATIONS

A search of her hospital room provided evidence of a self-inflicted disorder. Bacteremia with typical fecal flora had been caused by self-injected intravenous inoculation of stool and the esophageal ulcers by swallowed vinegar.

TREATMENT AND COURSE

The patient was initially treated with meropenem. After initial clinical and psychological stabilization the patient refused further psychiatric or psychosomatic treatment.

CONCLUSION

Fluctuating or bizarre symptoms and unusual diagnostic findings may indicate self-inflicted disorders, in which the symptoms of illness are caused by the afflicted person him/herself.

Genome-wide expression profiling in Escherichia coli K-12

We have established high resolution methods for global monitoring of gene expression in Escherichia coli. Hybridization of radiolabeled cDNA to spot blots on nylon membranes was compared to hybridization of fluorescently-labeled cDNA to glass microarrays for efficiency and reproducibility. A complete set of PCR primers was created for all 4290 annotated open reading frames (ORFs) from the complete genome sequence of E.coli K-12 (MG1655). Glass- and nylon-based arrays of PCR products were prepared and used to assess global changes in gene expression. Full-length coding sequences for array printing were generated by two-step PCR amplification. In this study we measured changes in RNA levels after exposure to heat shock and following treatment with isopropyl-beta-D-thiogalactopyranoside (IPTG). Both radioactive and fluorescence-based methods showed comparable results. Treatment with IPTG resulted in high level induction of the lacZYA and melAB operons. Following heat shock treatment 119 genes were shown to have significantly altered expression levels, including 35 previously uncharacterized ORFs and most genes of the heat shock stimulon. Analysis of spot intensities from hybridization to replicate arrays identified sets of genes with signals consistently above background suggesting that at least 25% of genes were expressed at detectable levels during growth in rich media.

Sibship size, sibship position, parental rearing and psychopathological manifestations in adults: preliminary analysis

Almost all investigations concerning the relationships between sibship size, sibship position and psychiatric disorders addressed more formal aspects, i.e. frequency and position, with contradictory and inconsistent results. Analyses considering sibship size and birth order as mediating factors between parental rearing and psychopathological manifestations in adults are lacking. The present results of an investigation of 1,013 psychiatric inpatients and 251 healthy volunteers support a systematic association between sibship size and parental rearing, mainly in terms of a reversed relationship between emotional warmth, overprotection and number of siblings. An excess of psychiatric patients in the middle position of a sibling seems to be related to specific unfavourable rearing patterns. A validation of our preliminary results would be required in terms of preventive measures for children of risk populations.

Evaluation of early diagnostic criteria for ankylosing spondylitis in a 10 year follow-up

A set of early diagnostic (ED) criteria comprising clinical data, ESR, radiological spinal signs, and the risk factor HLA B27 was evaluated after 5 and 10 years in a follow-up of 54 patients with an initial diagnosis of possible ankylosing spondylitis (AS). After 10 years 32 patients (59%) had developed definite AS according to the New York criteria, 10 individuals (19%) had possible or undifferentiated spondylarthropathy (SA), whereas in 12 patients (22%) other diagnoses were stated. ED criteria had a high discriminatory significance for the development of AS after 5 and 10 years (P less than 0.005, P less than 0.001 respectively). In this respect they were more valuable than B27 determination alone (P less than 0.01) or the ED criteria without HLA B27 (P less than 0.05). Furthermore, patients with still possible or undifferentiated SA had a higher mean score at the first examination than individuals with other final diagnosis (P less than 0.05). Thus, the ED criteria were useful for the identification of patients developing definite AS and of individuals in the AS related group of possible or undifferentiated SA.

Clinical features and prognosis of patients with possible ankylosing spondylitis. Results of a 10-year followup

Eighty-eight patients with possible ankylosing spondylitis (AS) were selected for this followup study. They showed normal or at most suspicious radiographic findings of the sacroiliac joints. After 5 years' followup, 24, and after 10 years 32 patients (59% of the 54 finally available, 36% of the 88 original patients) had definite AS. In 12 individuals, AS could be excluded. Of the 10 remaining patients, 6 still had possible, and 4 had undifferentiated spondyloarthropathy. A comparison between HLA-B27 positive and negative patients showed a significantly increased frequency of definite AS or possible and undifferentiated spondyloarthropathy (p less than 0.05) in the group of HLA-B27 positive patients. The development of AS was characterized by a prolonged course: radiological sacroiliitis became evident after at least 9 +/- 6 years, radiological signs of spinal involvement after 11 +/- 6 years mean disease duration. After 18 +/- 6 years 25 (78%) of 32 patients with AS still maintained good or sufficient functional capacity, indicating a good functional prognosis in the great majority of the patients.

Outcome of possible ankylosing spondylitis in a 10 years' follow-up study

Of 88 selected patients with possible ankylosing spondylitis (AS) 54 (61%) participated in two phases of a 10 years' follow-up study. Thirty-two (59%) developed definite AS according to the New York criteria, 10 (19%) had possible/undifferentiated seronegative spondylarthropathy (SSA) and 12 patients had other diagnoses. Only 3 (9%) of 35 patients with sacroiliitis did not fulfill the New York criteria for definite AS until the last examination. Sacroiliitis and radiological spinal signs of AS appeared rather late above a mean age of 40 years and after a mean disease duration of more than 10 years. After 18 years mean disease duration 25 (78%) of 32 AS patients had good or sufficient functional capacity indicating an overall good functional prognosis. HLA B27 typing proved to be useful in patients with possible early AS: 29 (71%) of 41 B27 positive and 3 (23%) of 13 B27 negative patients developed definite AS (p less than 0.005). A combination of the B27 test with data of the history, clinical, laboratory, and radiological examination proposed as early diagnostic criteria detected patients with the outcome diagnosis of definite AS with even higher significance (p less than 0.001). These criteria were also useful in the identification of patients with possible or undifferentiated SSA. The recently recognized entity of undifferentiated SSA should only be diagnosed after long term follow-up.

Evaluation of early diagnostic criteria including HLA-B27 for ankylosing spondylitis in a follow-up study

Early diagnostic criteria, a combination of the HLA-B27 test with clinical data, ESR and radiological signs, were evaluated in a 5-6 year follow-up study of 77 patients with possible ankylosing spondylitis (AS) and 45 with other rheumatic diseases. 34 (44%) with possible AS at first examination developed definite AS according to the New York criteria and 29 (38%) were classified as still possible AS. From these data a sensitivity of 82%, a specificity of 68%, a positive predictive value of 50% and a negative predictive value of 91% were calculated. Therefore the early diagnostic criteria, although of limited value for the diagnosis of definite AS, may clearly define patients at risk of AS or unclassified seronegative spondylarthropathies.