Publications by authors named "Martin Hessling"

33 Publications

Microbial Photoinactivation by Visible Light Results in Limited Loss of Membrane Integrity.

Antibiotics (Basel) 2021 Mar 23;10(3). Epub 2021 Mar 23.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, 89081 Ulm, Germany.

Interest in visible light irradiation as a microbial inactivation method has widely increased due to multiple possible applications. Resistance development is considered unlikely, because of the multi-target mechanism, based on the induction of reactive oxygen species by wavelength specific photosensitizers. However, the affected targets are still not completely identified. We investigated membrane integrity with the fluorescence staining kit LIVE/DEAD BacLight™ on a Gram positive and a Gram negative bacterial species, irradiating and with 405 nm and 450 nm. To exclude the generation of viable but nonculturable (VBNC) bacterial cells, we applied an ATP test, measuring the loss of vitality. Pronounced uptake of propidium iodide was only observed in at 405 nm. Transmission electron micrographs revealed no obvious differences between irradiated samples and controls, especially no indication of an increased bacterial cell lysis could be observed. Based on our results and previous literature, we suggest that visible light photoinactivation does not lead to rapid bacterial cell lysis or disruption. However, functional loss of membrane integrity due to depolarization or inactivation of membrane proteins may occur. Decomposition of the bacterial envelope following cell death might be responsible for observations of intracellular component leakage.
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http://dx.doi.org/10.3390/antibiotics10030341DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8005082PMC
March 2021

Photoinactivation of Staphylococci with 405 nm Light in a Trachea Model with Saliva Substitute at 37 °C.

Healthcare (Basel) 2021 Mar 11;9(3). Epub 2021 Mar 11.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, 89081 Ulm, Germany.

The globally observed rise in bacterial resistance against antibiotics has increased the need for alternatives to antibiotic treatments. The most prominent and important pathogen bacteria are the ESKAPE pathogens, which include among others , and . These species cause ventilator-associated pneumonia (VAP), which accounts for 24% of all nosocomial infections. In this study we tested the efficacy of photoinactivation with 405 nm violet light under conditions comparable to an intubated patient with artificial saliva for bacterial suspension at 37 °C. A technical trachea model was developed to investigate the visible light photoinactivation of as a non-pathogen surrogate of the ESKAPE pathogen (MRSA). The violet light was coupled into the tube with a fiber optic setup. The performed tests proved, that photoinactivation at 37 °C is more effective with a reduction of almost 3 log levels (99.8%) compared to 25 °C with a reduction of 1.2 log levels. The substitution of phosphate buffered saline (PBS) by artificial saliva solution slightly increased the efficiency during the experimental course. The increased efficiency might be caused by a less favorable environment for bacteria due to for example the ionic composition.
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http://dx.doi.org/10.3390/healthcare9030310DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998829PMC
March 2021

The impact of far-UVC radiation (200-230 nm) on pathogens, cells, skin, and eyes - a collection and analysis of a hundred years of data.

GMS Hyg Infect Control 2021 16;16:Doc07. Epub 2021 Feb 16.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, Germany.

The ongoing coronavirus pandemic requires new disinfection approaches, especially for airborne viruses. The 254 nm emission of low-pressure vacuum lamps is known for its antimicrobial effect, but unfortunately, this radiation is also harmful to human cells. Some researchers published reports that short-wavelength ultraviolet light in the spectral region of 200-230 nm (far-UVC) should inactivate pathogens without harming human cells, which might be very helpful in many applications. A literature search on the impact of far-UVC radiation on pathogens, cells, skin and eyes was performed and median log-reduction doses for different pathogens and wavelengths were calculated. Observed damage to cells, skin and eyes was collected and presented in standardized form. More than 100 papers on far-UVC disinfection, published within the last 100 years, were found. Far-UVC radiation, especially the 222 nm emission of KrCl excimer lamps, exhibits strong antimicrobial properties. The average necessary log-reduction doses are 1.3 times higher than with 254 nm irradiation. A dose of 100 mJ/cm reduces all pathogens by several orders of magnitude without harming human cells, if optical filters block emissions above 230 nm. The approach is very promising, especially for temporary applications, but the data is still sparse. Investigations with high far-UVC doses over a longer period of time have not yet been carried out, and there is no positive study on the impact of this radiation on human eyes. Additionally, far-UVC sources are unavailable in larger quantities. Therefore, this is not a short-term solution for the current pandemic, but may be suitable for future technological approaches for decontamination in rooms in the presence of people or for antisepsis.
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http://dx.doi.org/10.3205/dgkh000378DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894148PMC
February 2021

Inactivation Effect of Violet and Blue Light on ESKAPE Pathogens and Closely Related Non-pathogenic Bacterial Species - A Promising Tool Against Antibiotic-Sensitive and Antibiotic-Resistant Microorganisms.

Front Microbiol 2020 13;11:612367. Epub 2021 Jan 13.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, Germany.

Due to the globally observed increase in antibiotic resistance of bacterial pathogens and the simultaneous decline in new antibiotic developments, the need for alternative inactivation approaches is growing. This is especially true for the treatment of infections with the problematic ESKAPE pathogens, which include , and species, and often exhibit multiple antibiotic resistances. Irradiation with visible light from the violet and blue spectral range is an inactivation approach that does not require any additional supplements. Multiple bacterial and fungal species were demonstrated to be sensitive to this disinfection technique. In the present study, pathogenic ESKAPE organisms and non-pathogenic relatives are irradiated with visible blue and violet light with wavelengths of 450 and 405 nm, respectively. The irradiation experiments are performed at 37°C to test a potential application for medical treatment. For all investigated microorganisms and both wavelengths, a decrease in colony forming units is observed with increasing irradiation dose, although there are differences between the examined bacterial species. A pronounced difference can be observed between Acinetobacter, which prove to be particularly light sensitive, and enterococci, which need higher irradiation doses for inactivation. Differences between pathogenic and non-pathogenic bacteria of one genus are comparatively small, with the tendency of non-pathogenic representatives being less susceptible. Visible light irradiation is therefore a promising approach to inactivate ESKAPE pathogens with future fields of application in prevention and therapy.
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http://dx.doi.org/10.3389/fmicb.2020.612367DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7838345PMC
January 2021

Photoinactivation of the Coronavirus Surrogate phi6 by Visible Light.

Photochem Photobiol 2021 01 21;97(1):122-125. Epub 2020 Nov 21.

Ulm University of Applied Sciences, Ulm, Germany.

To stop the coronavirus spread, new inactivation approaches are being sought that can also be applied in the presence of humans or even on humans. Here, we investigate the effect of visible violet light with a wavelength of 405 nm on the coronavirus surrogate phi6 in two aqueous solutions that are free of photosensitizers. A dose of 1300 J cm of 405 nm irradiation reduces the phi6 plaque-forming unit concentration by three log-levels. The next step should be similar visible light photoinactivation investigations on coronaviruses, which cannot be performed in our lab.
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http://dx.doi.org/10.1111/php.13352DOI Listing
January 2021

Photoinactivation results of Enterococcus moraviensis with blue and violet light suggest the involvement of an unconsidered photosensitizer.

Biochem Biophys Res Commun 2020 12 29;533(4):813-817. Epub 2020 Sep 29.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, 89081, Germany.

Microorganisms can be photoinactivated with 405 and 450 nm irradiation, due to endogenous photosensitizers, which absorb light of these wavelengths and generate reactive oxygen species that destroy the cells from within. The photosensitizers assumed to be responsible are porphyrins in the spectral region around 405 nm and flavins at about 450 nm. The aim of this study was to investigate this hypothesis on enterococci, considering that they do not contain porphyrins. In photoinactivation experiments with Enterococcus moraviensis, 405 nm and 450 nm irradiation both led to a reduction of the bacterial concentration by several orders of magnitude with 405 nm irradiation being much more efficient. The measurement and analysis of the fluorescence spectra revealed no signs of porphyrins whereas flavins seemed to be rapidly converted to lumichrome by 405 nm radiation. Therefore, probably none of the usual suspects, porphyrins and flavins, was responsible for the photoinactivation of Enterococcus moraviensis during 405 nm irradiation. Fluorescence experiments revealed the spectra of lumichrome and NADH, which are both known photosensitizers. Presumably, one of them or both were actually involved here. As NADH and flavins (and therefore their photodegradation product lumichrome) are abundant in all microorganisms, they are probably also involved in 405 nm photoinactivation processes of other species.
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http://dx.doi.org/10.1016/j.bbrc.2020.09.091DOI Listing
December 2020

Enhancement of Contact Lens Disinfection by Combining Disinfectant with Visible Light Irradiation.

Int J Environ Res Public Health 2020 09 3;17(17). Epub 2020 Sep 3.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, 89081 Ulm, Germany.

Multiple use contact lenses have to be disinfected overnight to reduce the risk of infections. However, several studies demonstrated that not only microorganisms are affected by the disinfectants, but also ocular epithelial cells, which come into contact via residuals at reinsertion of the lens. Visible light has been demonstrated to achieve an inactivation effect on several bacterial and fungal species. Combinations with other disinfection methods often showed better results compared to separately applied methods. We therefore investigated contact lens disinfection solutions combined with 405 nm irradiation, with the intention to reduce the disinfectant concentration of ReNu Multiplus, OptiFree Express or AOSept while maintaining adequate disinfection results due to combination benefits. Pseudomonads, staphylococci and were studied with disk diffusion assay, colony forming unit (cfu) determination and growth delay. A log reduction of 4.49 was achieved for in 2 h for 40% ReNu Multiplus combined with an irradiation intensity of 20 mW/cm at 405 nm. For AOSept the combination effect was so strong that 5% of AOSept in combination with light exhibited the same result as 100% AOSept alone. Combination of disinfectants with visible violet light is therefore considered a promising approach, as a reduction of potentially toxic ingredients can be achieved.
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http://dx.doi.org/10.3390/ijerph17176422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7504152PMC
September 2020

Selection of parameters for thermal coronavirus inactivation - a data-based recommendation.

GMS Hyg Infect Control 2020 13;15:Doc16. Epub 2020 Jul 13.

Pharmpur GmbH, Koenigsbrunn, Germany.

Healthcare workers and large parts of the population are currently using personal protective equipment, such as face masks, to avoid infections with the novel coronavirus SARS-CoV-2. This equipment must be sterilized as gently as possible before reuse. One possibility is thermal inactivation, but professional autoclaves with their high temperatures are often not available or suitable. If the inactivation period is long enough, coronavirus inactivation can also be carried out at relatively low temperatures. The required duration was determined in this study. Data from published thermal inactivation studies on coronaviruses were applied to determine the temperature dependence of the rate constant k(T) for each coronavirus by employing Arrhenius models. The data obtained exhibit large variations, which appear to be at least partially caused by different sample properties. Samples with high protein content or samples in dry air sometimes seem to be more difficult to inactivate. Apart from this, the Arrhenius models describe the thermal inactivation properties well and SARS-CoV and SARS-CoV-2 can even be represented by a combined model. Furthermore, the available data suggest that all samples, including critical ones, can be mathematically included by a worst-case Arrhenius model. Coronaviruses can already be inactivated at relatively low temperatures. For most samples, application times of approximately 32.5, 3.7, and 0.5 minutes will be sufficient at 60°C, 80°C, and 100°C, respectively, for a 5 log-reduction. For difficult conditions, the worst-case model provides significantly longer application times of 490, 55, and 8 minutes for the temperatures mentioned.
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http://dx.doi.org/10.3205/dgkh000351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7373095PMC
July 2020

Ultraviolet irradiation doses for coronavirus inactivation - review and analysis of coronavirus photoinactivation studies.

GMS Hyg Infect Control 2020 14;15:Doc08. Epub 2020 May 14.

Pharmpur GmbH, Königsbrunn, Germany.

To slow the increasing global spread of the SARS-CoV-2 virus, appropriate disinfection techniques are required. Ultraviolet radiation (UV) has a well-known antiviral effect, but measurements on the radiation dose necessary to inactivate SARS-CoV-2 have not been published so far. Coronavirus inactivation experiments with ultraviolet light performed in the past were evaluated to determine the UV radiation dose required for a 90% virus reduction. This analysis is based on the fact that all coronaviruses have a similar structure and similar RNA strand length. The available data reveals large variations, which are apparently not caused by the coronaviruses but by the experimental conditions selected. If these are excluded as far as possible, it appears that coronaviruses are very UV sensitive. The upper limit determined for the log-reduction dose (90% reduction) is approximately 10.6 mJ/cm (median), while the true value is probably only 3.7 mJ/cm (median). Since coronaviruses do not differ structurally to any great exent, the SARS-CoV-2 virus - as well as possible future mutations - will very likely be highly UV sensitive, so that common UV disinfection procedures will inactivate the new SARS-CoV-2 virus without any further modification.
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http://dx.doi.org/10.3205/dgkh000343DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7273323PMC
May 2020

Pressure dependent direct transtissue transmission of eyewall, sclera and vitreous body in the range of 350-1050nm.

Z Med Phys 2020 Aug 4;30(3):201-210. Epub 2020 Mar 4.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, D-89081 Ulm, Germany. Electronic address:

Purpose: For transscleral application of optical radiation or light to the eye, it is important to know the transmission and absorbance of the tissue layers of the eyewall. The impact of photochemical energy to the retina located directly at the point of contact with the radiation emitter must be considered as well as the absorbance in choroid and retina. Therefore, the direct transmission of ex vivo porcine eyewalls and vitreous body were measured in this study.

Methods: At ex vivo porcine eyes (N=221) pressure dependent transmission measurements were performed with a pressure inducing setup. Pressure and wavelength dependent direct transmission of eyewall and vitreous body of porcine eyes were described for different applied pressures (23mmHg, 78mmHg and 132mmHg). The transmissions were investigated within the spectral range of 350-1050nm. In addition to the complete eyewall transmission measurements, the transmission of sclera, vitreous body and water was measured individually and the transmission of retina and choroid was calculated.

Results: With increasing wavelength and pressure, a significant transmission increase of the eyewall could be achieved (p<0.05). At 400nm and 132mmHg the transmission raised to 0.10%. At 1050nm it increased up to a value of 12.22%. In the visible spectrum, the direct transmission was always below 3.17%. The differences in eyewall transmission of eyes with different iris colors were significant at low pressure. With increasing pressure, the effect strength decreased and the differences lost their significance.

Conclusions: The pressure and wavelength dependent direct transmission of the eyewall and the vitreous body significantly increased with increasing pressure. This results are benefical for technical and clinical safety, research and development of illumination devices. It is necessary to know the intraocular brightness in the eye during diaphanoscopy, photocoagulation application to determine hazards.
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http://dx.doi.org/10.1016/j.zemedi.2020.02.003DOI Listing
August 2020

Realisation and assessment of a low-cost LED device for contact lens disinfection by visible violet light.

Biomed Tech (Berl) 2020 Aug;65(4):485-490

Ulm University of Applied Sciences, Institute of Medical Engineering and Mechatronics, Albert-Einstein-Allee 55, D-89081 Ulm, Germany.

This study presents a device for efficient, low-cost and eye-friendly overnight disinfection of contact lenses by visible violet light as an alternative to disinfection with biocide-containing solutions. Bacterial solutions with one Pseudomonas and one Staphylococcus strain each were irradiated for up to 8 h in commercial transparent contact lens cases by the presented light-emitting diode (LED) device. Samples were taken at different intervals and distributed on agar plates. The surviving bacteria were determined by counting of colony-forming units and compared to the specific requirements of the stand-alone test for contact lens disinfection of the hygiene standard ISO 14729. The concentration of both microorganisms was reduced by three orders of magnitude after less than 4 h of irradiation. The LED current and intensity have not yet been at maximum and could be further increased if necessary for other microorganisms. The presented device fulfils the requirement of the stand-alone test of the contact lens hygienic standard ISO 14729 for the tested Pseudomonas and Staphylococcus strains. According to literature data, the inactivation of Serratia marcescens, Candida albicans and Fusarium solani seems also possible, but may require increased LED current and intensity.
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http://dx.doi.org/10.1515/bmt-2019-0231DOI Listing
August 2020

Antimicrobial Effect of Visible Light-Photoinactivation of by Irradiation at 450, 470, and 620 nm.

Antibiotics (Basel) 2019 Oct 15;8(4). Epub 2019 Oct 15.

Ulm University of Applied Sciences, Department of Medical Engineering and Mechatronics, Albert-Einstein-Allee 55, D 89081 Ulm, Germany.

Despite the high number of legionella infections, there are currently no convincing preventive measures. Photoinactivation with visible light is a promising new approach and the photoinactivation sensitivity properties of planktonic to 450, 470, and 620 nm irradiation were thus investigated and compared to existing 405 nm inactivation data for obtaining information on responsible endogenous photosensitizers. Legionella were streaked on agar plates and irradiated with different doses by light emitting diodes (LEDs) of different visible wavelengths. When irradiating bacterial samples with blue light of 450 nm, a 5-log reduction could be achieved by applying a dose of 300 J cm, whereas at 470 nm, a comparable reduction required about 500 J cm. For red irradiation at 620 nm, no inactivation could be observed, even at 500 J cm. The declining photoinactivation sensitivity with an increasing wavelength is consistent with the assumption of porphyrins and flavins being among the relevant photosensitizers. These results were obtained for , but there is reason to believe that its inactivation behavior is similar to that of pathogenic legionella species. Therefore, this photoinactivation might lead to new future concepts for legionella reduction and prevention in technical applications or even on or inside the human body.
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http://dx.doi.org/10.3390/antibiotics8040187DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963517PMC
October 2019

Photoinactivation Sensitivity of Staphylococcus carnosus to Visible-light Irradiation as a Function of Wavelength.

Photochem Photobiol 2020 01 22;96(1):156-169. Epub 2019 Oct 22.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, Germany.

Inactivation properties of visible light are of increasing interest due to multiple possible fields of application concerning antibacterial treatment. For violet wavelengths, the generation of reactive oxygen species by porphyrins is accepted as underlying mechanism. However, there is still little knowledge about photosensitizers at blue wavelengths. While flavins were named as possible candidates, there is still no experimental evidence. This study investigates the photoinactivation sensitivity of Staphylococcus carnosus to selected wavelengths between 390 and 500 nm in 10- to 25-nm intervals. Absorption and fluorescence measurements in bacterial lysates confirmed inactivation findings. By means of a mathematical calculation in MATLAB , a fit of different photosensitizer absorption spectra to the measured action spectrum was determined to gain knowledge about the extent to which specific photosensitizers are involved. The most effective wavelength for S. carnosus at 415 nm could be explained by the involvement of zinc protoporphyrin IX. Between 450 and 470 nm, inactivation results indicated a broad plateau, statistically distinguishable from 440 and 480 nm. This observation points to flavins as responsible photosensitizers, which furthermore seem to be involved at violet wavelengths. A spectral scan of sensitivities might generally be an advantageous approach for examining irradiation impact.
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http://dx.doi.org/10.1111/php.13168DOI Listing
January 2020

Potential self-disinfection capacity of touch screen displays.

J Biophotonics 2019 10 15;12(10):e201900118. Epub 2019 Jul 15.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, Germany.

Touch screen displays are potential pathogen reservoirs and involved in the spread of hospital acquired infections. They emit visible light that is known for a weak but proven antimicrobial photoinactivation effect, so the question is whether displays have the potential to disinfect themselves. To test the antimicrobial capacity of touch screen displays, Staphylococcus carnosus are distributed on Samsung tablets and illuminated for up to 36 hours. The average number of colony forming units decreases with time with white light being the most efficient followed by blue, green and red light. Increasing the illumination intensity by a mirror leads to a faster bacterial decrease up to a 90% reduction in 15 hours. A 99.99% reduction of staphylococci should be possible by turning on the display over the weekend.
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http://dx.doi.org/10.1002/jbio.201900118DOI Listing
October 2019

Higher Risk of Light-Induced Retinal Damage Due to Increase of Intraocular Irradiance by Endoillumination.

Ophthalmol Ther 2019 Mar 17;8(1):41-50. Epub 2018 Dec 17.

Clinic of Ophthalmology, Bundeswehrkrankenhaus Ulm, Oberer Eselsberg 40, 89081, Ulm, Germany.

Introduction: All applied illumination systems are validated according to a standard that measures in an experimental setup the direct radiation intensity on a surface in an aqueous solution, not involving an eyeball. Due to various factors, multiple intraocular light-tissue interactions could occur and lead to retinal irradiation intensities that are higher than the irradiation caused by direct illumination. The aim of this work is to investigate the hypothesis that intraocular and technical reference irradiance is different.

Methods: Using an illumination system and a calibrated optical fiber, the irradiance in porcine eyes was measured at the posterior pole (macula) and compared with reference measurements. We compared two endoilluminators (spotlight and wide-angle) at a total of nine porcine eyes with a brown iris and five porcine eyes with a blue iris.

Results: The intraocular irradiance was always significantly higher compared to reference measurements (p < 0.001). Between eyes with a blue or brown iris, no significant difference was observed.

Conclusion: A significantly higher irradiance could be measured compared to a reference measurement with the same illumination setup. The intraocular illumination increased between 30 and 60%, dependent on the distance of the distal end of the light fiber (4-12-mm distance to the retina). This leads to the assumption that the so far allowed "safe" exposure times for illumination systems are overestimated and the potential hazard to the retina is higher.
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http://dx.doi.org/10.1007/s40123-018-0157-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6393251PMC
March 2019

Augmentation of 5-Aminolevulinic Acid Treatment of Glioblastoma by Adding Ciprofloxacin, Deferiprone, 5-Fluorouracil and Febuxostat: The CAALA Regimen.

Brain Sci 2018 Nov 22;8(12). Epub 2018 Nov 22.

Department of Neurosurgery, Ulm University Hospital, Albert-Einstein-Allee 23, D-89081 Ulm, Germany.

The CAALA (Complex Augmentation of ALA) regimen was developed with the goal of redressing some of the weaknesses of 5-aminolevulinic acid (5-ALA) use in glioblastoma treatment as it now stands. 5-ALA is approved for use prior to glioblastoma surgery to better demarcate tumor from brain tissue. 5-ALA is also used in intraoperative photodynamic treatment of glioblastoma by virtue of uptake of 5-ALA and its preferential conversion to protoporphyrin IX in glioblastoma cells. Protoporphyrin IX becomes cytotoxic after exposure to 410 nm or 635 nm light. CAALA uses four currently-marketed drugs-the antibiotic ciprofloxacin, the iron chelator deferiprone, the antimetabolite 5-FU, and the xanthine oxidase inhibitor febuxostat-that all have evidence of ability to both increase 5-ALA mediated intraoperative glioblastoma demarcation and photodynamic cytotoxicity of in situ glioblastoma cells. Data from testing the full CAALA on living minipigs xenotransplanted with human glioblastoma cells will determine safety and potential for benefit in advancing CAALA to a clinical trial.
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http://dx.doi.org/10.3390/brainsci8120203DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6315943PMC
November 2018

Short-Term Intraocular Pressure Rise during Locally Induced Force by Ophthalmologic Surgery Applications.

Ophthalmic Res 2019 31;61(3):159-167. Epub 2018 May 31.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, Germany.

Purpose: Surgical or diagnostic procedures are often accompanied by a short-term increase in intraocular pressure (IOP). A short-term increase in IOP can occur during refractive procedures, vitreoretinal surgery, transillumination, photocoagulation, or cryocoagulation. A porcine eye model was chosen (n = 89) to compile comparable study data and to de termine correlations between the force induced and the resulting intraocular pressure while excluding the effect of surgeons.

Methods: The IOP was measured in the anterior chamber. IOP changes were induced by applying an external force and measured when using a cannula, trocar, and cryocoagulation (n = 32), and correlations between force and resulting IOP were assessed (n = 57).

Results: A correlation was noted between the force induced and the IOP increase, which showed a linear dependency. The insertion of a 29-G cannula caused a mean ΔIOP value of 49.1 ± 2.9 mm Hg and an external force of 0.76 N, and that of a 23-G trocar 344.4 ± 5.9 mm Hg and 6.09 N, respectively. The rise in IOP during a simulated cryocoagulation reached values between 57.3 ± 14.8 mm Hg (cryoprobe tip diameter: 0.9 mm) and 130.3 ± 2.9 mm Hg (cryoprobe tip diameter: 7.0 mm).

Conclusion: The values of the forces applied can be converted into the resulting IOP based on the specific action. Surgical or diagnostic procedures should, therefore, be evaluated with regard to preexisting pathologies, such as glaucoma.
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http://dx.doi.org/10.1159/000488493DOI Listing
April 2019

An intraocular micro light-emitting diode device for endo-illumination during pars plana vitrectomy.

Eur J Ophthalmol 2019 Jan 29;29(1):75-81. Epub 2018 Mar 29.

1 Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Ulm, Germany.

Purpose:: Development of a new, fiber-free, single-use endo-illuminator for pars plana vitrectomy as a replacement for fiber-based systems with external light sources. The hand-guided intraocularly placed white micro light-emitting diode is evaluated for its illumination properties and potential photochemical and thermal hazards.

Methods:: A micro light-emitting diode was used to develop a single-use intraocular illumination system. The light-source-on-tip device was implemented in a prototype with 23G trocar compatible outer diameter of 0.6 mm. The experimental testing was performed on porcine eyes. All calculations of possible photochemical and thermal hazards during the application of the intraocular micro light-emitting diode were calculated according to DIN EN ISO 15007-2: 2014.

Results:: The endo-illuminator generated a homogeneous and bright illumination of the intraocular space. The color impression was physiologic and natural. Contrary to initial apprehension, the possible risk caused by inserting a light-emitting diode into the intraocular vitreous was much smaller when compared to conventional fiber-based illumination systems. The photochemical and thermal hazards allowed a continuous exposure time to the retina of at least 4.7 h.

Conclusion:: This first intraocular light source showed that a light-emitting diode can be introduced into the eye. The system can be built as single-use illumination system. This light-source-on-tip light-emitting diode-endo-illumination combines a chandelier wide-angle illumination with an adjustable endo-illuminator.
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http://dx.doi.org/10.1177/1120672118757618DOI Listing
January 2019

Location and pressure dependent transmission of human and porcine sclera: an anterior to posterior examination.

Graefes Arch Clin Exp Ophthalmol 2017 Nov 5;255(11):2185-2198. Epub 2017 Aug 5.

Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, D-89081, Ulm, Germany.

Purpose: For diaphanoscopy or transscleral laser applications, the transmission of the sclera is an essential property. The study aimed to determine the pressure dependent transmission of human sclera from anterior to posterior.

Methods: Pressure dependent transmission measurements were performed by a pressure inducing setup at the range of 60-2058 kPa. The transmissions were measured within spectral range of 350-1100 nm. Specimens of human sclera were taken from corneo-scleral transplants. Those compounds were obtained at pars plicata residual sclera tissue. For an anterior to posterior examination of transmission, samples were taken from halved eye globes, which were formerly fixed in formalin.

Results: The pressure dependent transmission increased with rising load at all measured wavelengths for human sclera samples. The highest increase was observed for short wavelengths. With rising pressure, the increase of transmission aimed for a steady state. This behavior was fitted by a limited growing function. With an inducing burden of 2058 kPa, the steady state was already reached and exhibited an increase in transmission factor of 4.1 at 400 nm and 1.8 at 1000 nm. The anterior to posterior measurements of human sclera fixed in formalin were not corresponding to the results of the other human samples. For the porcine samples, the transmission increased from anterior to the equator of the eye globe. Further posterior the transmission decreased and rose again to N. opticus. With rising pressure, the transmission increased at all wavelengths and all locations. Posterior from the equator, with higher pressure the transmission became superior compared to anterior.

Conclusions: The results of human sclera fixed in formalin could be related to formalin-induced cross-linking between the collagen fibers. Because of doubt about the physiological behavior of formalin-fixed samples, formalin-free porcine postmortem eye globes were also probed having a very similar thickness and histological structure as human sclera, so the results could be set in relation to human probes. These results can now be used to create an eye-map to determine maximum possible retina irradiation or illumination durations for transscleral applications in eye surgery.
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http://dx.doi.org/10.1007/s00417-017-3758-yDOI Listing
November 2017

Transscleral LED illumination pen.

Biomed Eng Lett 2017 Nov 21;7(4):311-315. Epub 2017 Jun 21.

3Ulm University of Applied Sciences, Albert-Einstein-Allee 55, 89081 Ulm, Germany.

Existing light sources for intraocular illumination are often bulky and expensive and pose a risk for the patient, because light guides are inserted in the eye through incisions and if the tip of these light guides get too close to the retina, the retina can be damaged photochemically within minutes or even seconds. Therefore a new, safe and simple device for intraocular illumination is developed and evaluated for its thermal and photochemical risks to the patient. It consists of a white LED which is integrated into a pen like holder. This device is pressed against the sclera by the physician who seeks for illumination during surgery or for diagnostic purposes. The LED light is transmitted through the sclera without the need for an incision. Considering the relevant standards, the device poses no harm to the patient, and in tests with the authors' own eyes a sufficient intraocular illumination is reached. The proposed device is quite simple but easy to handle and very gentle for the patient.
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http://dx.doi.org/10.1007/s13534-017-0039-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208513PMC
November 2017

UV-C inactivation of Legionella rubrilucens.

GMS Hyg Infect Control 2017 10;12:Doc06. Epub 2017 Apr 10.

Ulm University of Applied Sciences, Ulm, Germany.

Despite the great health significance of , there is only little information on their UV sensitivity. Besides only has been investigated so far. In this study has been spread on buffered charcoal yeast extract agar and irradiated with the 254 nm UV-C emission of a mercury vapor lamp. The disinfection success is measured by colony counting after incubation and comparison of the number of colonies on irradiated and unirradiated reference agar plates. The average log-reduction dose is 1.08 mJ/cm for free , which is at the lower end of the so far published Legionella log-reduction values, but all three species show similar UV-C sensitivities. The log-reduction dose of legionellae in amoebae has not been investigated, but with the observed high UV-C sensitivity for free , the idea of a future point-of-use disinfection by small UV-C LEDs in water-taps or shower heads appears to be realistic, even if legionellae are more resistant in amoebae.
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http://dx.doi.org/10.3205/dgkh000291DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5388836PMC
April 2017

Automated bioreactor system for cartilage tissue engineering of human primary nasal septal chondrocytes.

Biomed Tech (Berl) 2017 Oct;62(5):481-486

.

An automated bioreactor system for three-dimensional (3D) cultivation of facial cartilage replacement matrices (e.g. whole human auricles) with automatised medium exchange, gas flow and temperature control was developed. The measurement of O2 saturation and pH value in the medium was performed with a non-invasive optical method. The whole system can be observed via remote monitoring worldwide. First results demonstrated that the complete system remained sterile throughout a period of 42 days. Human chondrocytes migrated into the employed cartilage replacement matrix consisting of decellularised porcine nasoseptal cartilage (pNSC). Furthermore, an improved migration and new synthesis of aggrecan was detected. A first evaluation of the system was conducted by comparison of the results from laboratory analysis with computational fluid dynamics (CFD).
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http://dx.doi.org/10.1515/bmt-2015-0248DOI Listing
October 2017

Improved contact lens disinfection by exposure to violet radiation.

Technol Health Care 2016 ;24(1):145-51

Background: Conventional procedures for contact lens disinfection, based on solutions with aggressive chemical ingredients, not only affect microorganisms but operate likewise damaging towards the epithelial eye surface.

Objective: The aim of this study was to evaluate the applicability of an alternative or complementary disinfection procedure for contact lenses based on irradiation within the visible wavelength range.

Methods: Suspensions of S. auricularis, B. subtilis and E. coli were exposed to 405 nm irradiation, for determining the disinfection efficacy. Surviving rates were analyzed by membrane filtration as well as a semi-quantitative analysis using DipSlides.

Results: A significant antibacterial effect of the 405 nm irradiation is verifiable for all probed bacteria. Using S. auricularis, there has been no colony forming after an irradiation exposure of 2 hours.

Conclusion: The hitherto existing results give reason for the assumption that violet LEDs integrated in contact lens cases will provide a subsidiary disinfection activity and maybe even offer the reduction of chemical ingredients in lens cleaning solutions to become gentler to the eye. In addition the danger of a rerise of the germ concentration after the completion of the disinfection procedure will be reduced.
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http://dx.doi.org/10.3233/THC-151104DOI Listing
January 2017

An extraocular non-invasive transscleral LED-endoilluminator for eye speculum integration.

Graefes Arch Clin Exp Ophthalmol 2015 Sep 10;253(9):1529-35. Epub 2015 May 10.

Department of Mechatronics and Medical Engineering, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, D-89081, Ulm, Germany.

Purpose: Conventional chandelier-endoilluminators used for pars-plana vitrectomy consist of a light-emitting tip attached to an optical fibre. The tip requires introduction into the ocular space through an incision. To achieve complete illumination of the intraocular space, the introduction of more than just one tip is sometimes necessary. An extraocular vitreoretinal LED-endoilluminator discussed in this paper represents a new approach to illuminate the intraocular space. The light source is integrated into a speculum and firmly apposed to the sclera. This approach offers the advantage of effectively illuminating the interior of the eye even though the procedure is non-invasive. Furthermore, this approach significantly reduces the risk of damage to the retina by phototoxic effects.

Methods: A round white LED was used as a light source. By integrating the light source into a speculum, the LED was firmly held against the sclera. Thus, the ocular space was illuminated transsclerally. As a result, indirect uniform illumination of the complete intraocular space was achieved. The prototype was developed considering the relevant international standards. Porcine eyes were used because their properties are similar to those of human eyes.

Results: Porcine eyes could be acceptably illuminated with the selected LED. The LED-endoilluminator conforms with international standards for endoillumination. Thus, possible photochemical and thermal risks are considered and reduced to a minimum.

Conclusions: A novel LED-endoilluminator which can be attached to a speculum was developed. The system does not need any connection to an external light source and, consequently, also avoids usage of an optical fibre. Regular and uniform illumination of the intraocular space was achieved by transmitted and scattered visible irradiation, avoiding an incision. The duration of potential light exposure, compared to existing illumination systems, can be significantly increased. This is also true when the illuminator is not directly placed over the pars-plana and the distance to the retina is reduced. Only a part of the light reaches the retina and the fraction of short wavelength becomes very small. Increased safety of the system results from now being able to increase the exposure time and reduce phototoxic stress to the retina.
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http://dx.doi.org/10.1007/s00417-015-3036-9DOI Listing
September 2015

Chaperone-interacting TPR proteins in Caenorhabditis elegans.

J Mol Biol 2013 Aug 29;425(16):2922-39. Epub 2013 May 29.

Center for Integrated Protein Science Munich and Department of Chemistry, Technische Universität München, 85747 Garching, Germany.

The ATP-hydrolyzing molecular chaperones Hsc70/Hsp70 and Hsp90 bind a diverse set of tetratricopeptide repeat (TPR)-containing cofactors via their C-terminal peptide motifs IEEVD and MEEVD. These cochaperones contribute to substrate turnover and confer specific activities to the chaperones. Higher eukaryotic genomes encode a large number of TPR-domain-containing proteins. The human proteome contains more than 200 TPR proteins, and that of Caenorhabditis elegans, about 80. It is unknown how many of them interact with Hsc70 or Hsp90. We systematically screened the C. elegans proteome for TPR-domain-containing proteins that likely interact with Hsc70 and Hsp90 and ranked them due to their similarity with known chaperone-interacting TPRs. We find C. elegans to encode many TPR proteins, which are not present in yeast. All of these have homologs in fruit fly or humans. Highly ranking uncharacterized open reading frames C33H5.8, C34B2.5 and ZK370.8 may encode weakly conserved homologs of the human proteins RPAP3, TTC1 and TOM70. C34B2.5 and ZK370.8 bind both Hsc70 and Hsp90 with low micromolar affinities. Mutation of amino acids involved in EEVD binding disrupts the interaction. In vivo, ZK370.8 is localized to mitochondria in tissues with known chaperone requirements, while C34B2.5 colocalizes with Hsc70 in intestinal cells. The highest-ranking open reading frame with non-conserved EEVD-interacting residues, F52H3.5, did not show any binding to Hsc70 or Hsp90, suggesting that only about 15 of the TPR-domain-containing proteins in C. elegans interact with chaperones, while the many others may have evolved to bind other ligands.
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http://dx.doi.org/10.1016/j.jmb.2013.05.019DOI Listing
August 2013

A fully synthetic human Fab antibody library based on fixed VH/VL framework pairings with favorable biophysical properties.

MAbs 2013 May-Jun;5(3):445-70. Epub 2013 Apr 9.

MorphoSys AG; Martinsried/Planegg, Germany.

This report describes the design, generation and testing of Ylanthia, a fully synthetic human Fab antibody library with 1.3E+11 clones. Ylanthia comprises 36 fixed immunoglobulin (Ig) variable heavy (VH)/variable light (VL) chain pairs, which cover a broad range of canonical complementarity-determining region (CDR) structures. The variable Ig heavy and Ig light (VH/VL) chain pairs were selected for biophysical characteristics favorable to manufacturing and development. The selection process included multiple parameters, e.g., assessment of protein expression yield, thermal stability and aggregation propensity in fragment antigen binding (Fab) and IgG1 formats, and relative Fab display rate on phage. The framework regions are fixed and the diversified CDRs were designed based on a systematic analysis of a large set of rearranged human antibody sequences. Care was taken to minimize the occurrence of potential posttranslational modification sites within the CDRs. Phage selection was performed against various antigens and unique antibodies with excellent biophysical properties were isolated. Our results confirm that quality can be built into an antibody library by prudent selection of unmodified, fully human VH/VL pairs as scaffolds.
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http://dx.doi.org/10.4161/mabs.24218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4169037PMC
April 2015

Asymmetric activation of the hsp90 dimer by its cochaperone aha1.

Mol Cell 2010 Feb;37(3):344-54

Center for Integrated Protein Science Munich at the Department Chemie, Technische Universität München, D-85747 Garching, Germany.

The chaperone Hsp90 is an ATP-dependent, dimeric molecular machine regulated by several cochaperones, including inhibitors and the unique ATPase activator Aha1. Here, we analyzed the mechanism of the Aha1-mediated acceleration of Hsp90 ATPase activity and identified the interaction surfaces of both proteins using multidimensional NMR techniques. For maximum activation of Hsp90, the two domains of Aha1 bind to sites in the middle and N-terminal domains of Hsp90 in a sequential manner. This binding induces the kinetically unfavored N terminally dimerized state of Hsp90, which primes for the hydrolysis-competent conformation. Surprisingly, this activation mechanism is asymmetric. The presence of one Aha1 molecule per Hsp90 dimer is sufficient to bridge the two subunits and to fully stimulate Hsp90 ATPase activity. This seems to functionalize the two subunits of the Hsp90 dimer in different ways, in that one subunit can be used for conformational ATPase regulation and the other for substrate protein processing.
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http://dx.doi.org/10.1016/j.molcel.2010.01.006DOI Listing
February 2010

Hsp90 charged-linker truncation reverses the functional consequences of weakened hydrophobic contacts in the N domain.

Nat Struct Mol Biol 2009 Nov 18;16(11):1141-7. Epub 2009 Oct 18.

Urologic Oncology Branch, National Cancer Institute, Bethesda, Maryland, USA.

Heat shock protein 90 (Hsp90) is an essential molecular chaperone in eukaryotes, as it regulates diverse signal transduction nodes that integrate numerous environmental cues to maintain cellular homeostasis. Hsp90 also is secreted from normal and transformed cells and regulates cell motility. Here, we have identified a conserved hydrophobic motif in a beta-strand at the boundary between the N domain and charged linker of Hsp90, whose mutation not only abrogated Hsp90 secretion but also inhibited its function. These Hsp90 mutants lacked chaperone activity in vitro and failed to support yeast viability. Notably, truncation of the charged linker reduced solvent accessibility of this beta-strand and restored chaperone activity to these mutants. These data underscore the importance of beta-strand 8 for Hsp90 function and demonstrate that the functional consequences of weakened hydrophobic contacts in this region are reversed by charged-linker truncation.
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http://dx.doi.org/10.1038/nsmb.1682DOI Listing
November 2009

The large conformational changes of Hsp90 are only weakly coupled to ATP hydrolysis.

Nat Struct Mol Biol 2009 Mar 22;16(3):281-6. Epub 2009 Feb 22.

Physik-Department, IMETUM, CeNS, James-Franck-Strasse 1, 85748 Garching, Germany.

The molecular chaperone heat-shock protein 90 (Hsp90) is one of the most abundant proteins in unstressed eukaryotic cells. Its function is dependent on an exceptionally slow ATPase reaction that involves large conformational changes. To observe these conformational changes and to understand their interplay with the ATPase function, we developed a single-molecule assay that allows examination of yeast Hsp90 dimers in real time under various nucleotide conditions. We detected conformational fluctuations between open and closed states on timescales much faster than the rate of ATP hydrolysis. The compiled distributions of dwell times allow us to assign all rate constants to a minimal kinetic model for the conformational changes of Hsp90 and to delineate the influence of ATP hydrolysis. Unexpectedly, in this model ATP lowers two energy barriers almost symmetrically, such that little directionality is introduced. Instead, stochastic, thermal fluctuations of Hsp90 are the dominating processes.
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http://dx.doi.org/10.1038/nsmb.1557DOI Listing
March 2009

Dissection of the ATP-induced conformational cycle of the molecular chaperone Hsp90.

Nat Struct Mol Biol 2009 Mar 22;16(3):287-93. Epub 2009 Feb 22.

Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.

The molecular chaperone heat-shock protein 90 (Hsp90) couples ATP hydrolysis to conformational changes driving a reaction cycle that is required for substrate activation. Recent structural analysis provided snapshots of the open and closed states of Hsp90, which mark the starting and end points of these changes. Using fluorescence resonance energy transfer (FRET), we dissected the cycle kinetically and identified the intermediates on the pathway. The conformational transitions are orders of magnitude slower than the ATP-hydrolysis step and thus are the limiting events during the reaction cycle. Furthermore, these structural changes can be tightly regulated by cochaperones, being completely inhibited by Sti1 or accelerated by Aha1. In fact, even in the absence of nucleotide, Aha1 induces Hsp90 rearrangements that speed up the conformational cycle. This comprehensive reconstitution of the Hsp90 cycle defines a controlled progression through distinct intermediates that can be modulated by conformation-sensitive cochaperones.
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http://dx.doi.org/10.1038/nsmb.1565DOI Listing
March 2009