Photoinactivation by UVA radiation and visible light of Candida auris compared to other fungi.

In addition to the rising number of patients affected by viruses and bacteria, the number of fungal infections has also been rising over the years. Due to the increase in resistance to various antimycotics, investigations into further disinfection options are important. In this study, two yeasts (Candida auris and Saccharomyces cerevisiae) and a mold (Cladosporium cladosporioides) were irradiated at 365, 400, and 450 nm individually. The resulting log 1 reduction doses were determined and compared with other studies. Furthermore, fluorescence measurements of C. auris were performed to detect possible involved photosensitizers. A roughly exponential photoinactivation was observed for all three fungi and all irradiation wavelengths with higher D90 doses for longer wavelengths. The determined log 1 reduction doses of C. auris and S. cerevisiae converged with increasing wavelength. However, S. cerevisiae was more photosensitive than C. auris for all irradiation wavelengths and is therefore not a suitable C. auris surrogate for photoinactivation experiments. For the mold C. cladosporioides, much higher D90 doses were determined than for both yeasts. Concerning potential photosensitizers, flavins and various porphyrins were detected by fluorescence measurements. By excitation at 365 nm, another, so far unreported fluorophore and potential photosensitizer was also observed. Based on its fluorescence spectrum, we assume it to be thiamine.Graphic abstract.

Influence of Visible Violet, Blue and Red Light on the Development of Cataract in Porcine Lenses.

Background and Objectives: Cataract is a disease that is globally prevalent in today's population and occurs mostly in the elderly. It is an opacity of the lens that worsens vision and can lead to blindness. One well-known risk factor of cataract is ultraviolet (UV) radiation. However, increasing exposure to modern artificial light sources like light emitting diodes (LEDs) and displays might have an impact on cataract formation due to possible high (and hidden) blue radiation. An ex-vivo study indicates that intense blue radiation causes cataract in porcine lenses. The goal of this work is the investigation whether violet or red light also lead to cataract formation in porcine lenses and to compare the impact of the different wavelengths. Materials and Methods: LEDs with wavelengths of 407 nm (violet), 463 nm (blue) and 635 nm (red) are used to irradiate ex-vivo porcine lenses with a dose of 6 kJ/cm2. Before and after irradiation the lens transmissions are measured and dark field images are taken to determine cataract formation. The same procedure is performed for unirradiated controls. Results: The results of the transmission measurements are in accordance with the results of the dark field images and state that 635 nm (red) is inducing no or only weak cataract. In comparison to the dark field images the transmission measurements exhibit stronger cataract formation for 407 nm than for 463 nm irradiation while the dark field images show similar cataract formation for both wavelengths. Conclusions: Visible light of short wavelengths cause cataract formation in porcine eyes, and it cannot be excluded that these wavelengths, which are emitted by modern LED illuminants, also pose a danger to human eyes.

Cataract Development by Exposure to Ultraviolet and Blue Visible Light in Porcine Lenses.

Background and Objectives: Cataract is still the leading cause of blindness. Its development is well researched for UV radiation. Modern light sources like LEDs and displays tend to emit blue light. The effect of blue light on the retina is called blue light hazard and is studied extensively. However, its impact on the lens is not investigated so far. Aim: Investigation of the impact of the blue visible light in porcine lens compared to UVA and UVB radiation. Materials and Methods: In this ex-vivo experiment, porcine lenses are irradiated with a dosage of 6 kJ/cm2 at wavelengths of 311 nm (UVB), 370 nm (UVA), and 460 nm (blue light). Lens transmission measurements before and after irradiation give insight into the impact of the radiation. Furthermore, dark field images are taken from every lens before and after irradiation. Cataract development is illustrated by histogram linearization as well as faults coloring of recorded dark field images. By segmenting the lens in the background's original image, the lens condition before and after irradiation could be compared. Results: All lenses irradiated with a 6 kJ/cm2 reveal cataract development for radiation with 311 nm, 370 nm, and 460 nm. Both evaluations reveal that the 460 nm irradiation causes the most cataract. Conclusion: All investigated irradiation sources cause cataracts in porcine lenses-even blue visible light.

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

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.

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

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.

Asymmetric activation of the hsp90 dimer by its cochaperone aha1.

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.

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

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.

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

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.

Advancement of a RGBW-LED pen for diaphanoscopic illumination with adjustable color and intensity with tests on ex-vivo porcine eyes in terms of retinal risk and correlated color temperature.

Diaphanoscopic illumination has the disadvantage that the intraocular spectrum is red-shifted due to transmission properties of the eyewall. This red-shift should be counteracted as well as the retinal risk should be reduced with adjusting the spectral distribution of the illumination light. Likewise, the illumination spectrum has to be adapted to the eye color of the patient. With the further development of a red, green, blue and white light-emitting diode (RGBW-LED) diaphanoscopy pen, the intensities of each color can be varied. The functionality of the LED pen is tested on ex-vivo porcine eyes. By measuring the transmission of the sclera and choroidea, the photochemical and thermal retinal hazard and the maximum exposure time are determined according to the standard DIN EN ISO 15004-2:2007. With this RGBW-LED pen the intraocular space can be illuminated clearly of up to 1.5 h without potential retinal damage according to DIN EN ISO 15004:2-2007. By adjusting the illumination spectrum the red-shift can be compensated and retinal risk can be reduced. By varying the LED intensities, the correlated color temperature in the eye can also be varied from cold white to warm white appearance as comfortable to the ophthalmologist. Additionally, a simple adjustment of the illumination to the eye color of the patient is possible. Using this RGBW-LED pen, the ophthalmologist can set the desired intraocular color appearance, which he prefers for special applications. He could also adjust the illumination to the eye color as this would reduce retinal hazard.

Photoinactivation of the bacteriophage PhiX174 by UVA radiation and visible light in SM buffer and DMEM-F12.

OBJECTIVE: It has been observed that viruses can be inactivated by UVA radiation and visible light. The aim of this study is to investigate whether a medium that contains a photosensitizer might have an influence on viral reduction under irradiation by UVA, violet or blue light. Test virus is the bacteriophage PhiX174 in the photosensitizer-free SM buffer and DMEM-F12, which contains the known photosensitizer riboflavin. RESULTS: The determined PhiX174 D90 doses in SM buffer and DMEM were 36.8 J/cm² and 13.6 J/cm² at 366 nm, 153.6 J/cm² and 129.1 J/cm² at 408 nm and 4988 J/cm² and 2477.1 J/cm² at 455 nm, respectively. It can be concluded that the medium has a large influence on the results. This might be caused by the photosensitizer riboflavin in DMEM-F12. As riboflavin is a key component in many cell culture media, irradiation experiments with viruses in cell culture media should be avoided if the investigation of intrinsical photoinactivation properties of viruses is aimed for.

Determination of Correlated Color Temperature in Ex Vivo Porcine Eyes during Intraocular Illumination.

(1) Background: In ophthalmic surgery, white light is mostly applied to illuminate the intraocular space, and ophthalmologists are comfortable working with it. Diaphanoscopic illumination changes the spectral composition of light, resulting in a change in the correlated color temperature (CCT) of the intraocular illumination. This color change makes it difficult for surgeons to recognize the structures in the eye. CCT during intraocular illumination has not yet been measured before, and it is the aim of this study to perform such measurement. (2) Methods: CCT was measured inside ex vivo porcine eyes during diaphanoscopic illumination and endoillumination using a current ophthalmic illumination system with a detection fiber inside the eye. By applying pressure on the eye with a diaphanoscopic fiber, the dependency of CCT on pressure was examined. (3) Results: The intraocular CCT values during endoillumination were 3923 K and 5407 K for the halogen and xenon lamps, respectively. During diaphanoscopic illumination, a strong unwanted red shift was observed, resulting in 2199 K and 2675 K for the xenon and the halogen lamps, respectively. Regarding different applied pressures, the CCT did not differ considerably. (4) Conclusions: This red shift should be compensated for in the development of new illumination systems since surgeons are used to white light illumination, which also simplifies the identification of retinal structures.

Far-UVC Radiation for Disinfecting Hands or Gloves?

(1) Background: Far-UVC radiation in the spectral range 200-230 nm has, according to previous findings, a strong antimicrobial effect on pathogens, but exhibits hardly any harmful effect on human skin. Therefore, the present study will discuss whether such radiation could also be suitable for hand disinfection in the healthcare sector. (2) Methods: Hands and gloves were microbially contaminated and exposed to radiation from a 222 nm krypton-chloride-excimer lamp. The applied doses were 23 mJ/cm2 and 100 mJ/cm2, respectively. Irradiated and non-irradiated hands and gloves were pressed onto agar plates and colonies were counted and compared after 24 h of incubation. For comparison, we also treated hands and gloves with a commercial liquid alcohol-based disinfectant. (3) Results: On the hand, the 23 mJ/cm2 resulted in the reduction of the observed colonies on the agar plates by one log level. For the gloves irradiated with 100 mJ/cm2, a colony reduction of 1.3 log levels was recorded. In the comparative experiments with the commercial disinfectant, a colony reduction of 1.9 and approximately one log level was observed on hand and gloves, respectively. (4) Conclusion: In both cases, far-UVC radiation provided a considerable reduction in microorganisms. However, compared to published far-UVC irradiation results in suspensions, the disinfection success on hands and gloves was rather low. With regard to the irradiation limits currently existing in the European Union, multiple daily hand disinfection with far-UVC radiation is actually legally not possible at present, but the thresholds are currently under discussion and could change in the future. Far-UVC disinfection of hands in gloves seems theoretically possible if attention is paid to potential perforations in the gloves.

UV radiation sensitivity of bacteriophage PhiX174 - A potential surrogate for SARS-CoV-2 in terms of radiation inactivation.

To minimize health risks, surrogates are often employed to reduce experiments with pathogenic microorganisms and the associated health risk. Due to structural similarities between the enveloped RNA-viruses SARS-CoV-2 and Phi6, the latter has been established as a nonpathogenic coronavirus surrogate for many applications. However, large discrepancies in the UV log-reduction doses between SARS-CoV-2 and Phi6 necessitate the search for a better surrogate for UV inactivation applications. A literature study provided the bacteriophage PhiX174 as a potentially more suitable nonpathogenic coronavirus surrogate candidate. In irradiation experiments, the sensitivity of PhiX174 was investigated upon exposure to UV radiation of wavelengths 222 nm (Far-UVC), 254 nm (UVC), 302 nm (broad-band UVB), 311 nm (narrow-band UVB) and 366 nm (UVA) using a plaque assay. The determined log-reduction doses for PhiX174 were 1.3 mJ/cm2 @ 222 nm, 5 mJ/cm2 @ 254 nm, 17.9 mJ/cm2 @ 302 nm, 625 mJ/cm2 @ 311 nm and 42.5 J/cm2 @ 366 nm. The comparison of these results with published log-reduction doses of SARS-CoV-2 in the same spectral region, led to the conclusion that the bacteriophage PhiX174 exhibits larger log-reduction doses than SARS-CoV-2, nevertheless, it is a better UV-surrogate at 222 nm (Far-UVC), 254 nm (UVC) and 302 nm (UVB) than the often applied Phi6.

Reutilization of disposable rebound tonometer probes: Risk or return?

Purpose: An advantage of rebound tonometry (RT) is its ease of use so that it can also be operated by health care technicians. However, the cost of the disposable measuring probes is high and their reuse carries the risk of infection. Therefore, this study aims to objectify the potential risk of bacterial transmission by RT. Methods: Our experimental setting consisted of two experiments. The first aimed to quantify the number of bacteria on a tonometer probe after immersion in a bacterial suspension in vitro. The experiment was carried out with two different bacteria and compared with results from a Goldmann tonometer probe. The second experiment tested whether bacteria could be transmitted by simulating reuse of a nondisinfected rebound tonometer probe. Results: First experiment: After immersion of the rebound tonometer probe, we measured a bacterial count of 2.43 × 106 Escherichia coli (EC) and 1.12 × 106 Pseudomonas fluorescens. In total, 1.09 × 107 bacteria for EC and 2.61 × 106 for Pseudomonas fluorescens (PF) were measured on the Goldmann tonometer probe. Second experiment: A bacterial transmission could be detected in 36% of cases in which reuse of nondisinfected tonometer probes was simulated. Conclusion: These results show that despite the small surface of the rebound tonometer probe, there is a clear risk of bacterial transmission. Thorough disinfection according to general standards should be mandatory if the tonometer probes are to be reused.

Investigation on Potential ESKAPE Surrogates for 222 and 254 nm Irradiation Experiments.

Background: Due to the increase in multidrug-resistant pathogens, it is important to investigate further antimicrobial options. In order not to have to work directly with pathogens, the investigation of possible surrogates is an important aspect. It is examined how suitable possible surrogate candidates for ESKAPE pathogens are for UVC applications. In addition, the inactivation sensitivities to 222 and 254 nm radiation are compared in relation. Methods: Non-pathogenic members (Enterococcus mundtii, Staphylococcus carnosus, Acinetobacter kookii, Pseudomonas fluorescens and Escherichia coli) of genera of ESKAPE strains were photoinactivated in PBS with irradiation wavelengths of 222 and 254 nm (no non-pathogenic Klebsiella was available). Log reduction doses were determined and compared to published photoinactivation results on ESKAPE pathogens. It was assumed that non-pathogenic bacteria could be designated as surrogates for one wavelength and one ESKAPE strain, if the doses were between the 25 and 75% quantiles of published log reduction dose of the corresponding pathogen. Results: For all non-pathogen relatives (except A. kookii), higher average log reduction doses were required for irradiation at 222 nm than at 254 nm. Comparison by boxplot revealed that five of eight determined log reduction doses of the possible surrogates were within the 25 and 75% quantiles of the data for ESKAPE pathogens. The measured log reduction dose for non-pathogenic E. coli was above the 75% quantile at 222 nm, and the log reduction dose for S. carnosus was below the 25% quantile at 254 nm. Conclusion: For more than half of the studied cases, the examined ESKAPE relatives in this study can be applied as surrogates for ESKAPE pathogens. Because of lack of data, no clear statement could be made for Enterococcus faecalis at 222 nm and Acinetobacter baumannii at both wavelengths.

Intraocular reflectance of the ocular fundus and its impact on increased retinal hazard.

PURPOSE: Inside the eye light can be reflected multiple times due to light-tissue interactions and the spherical geometry of the eye. Due to these optical properties, a defined retinal area is not only illuminated by direct light but also by indirect, reflected light from the inner side of the eyewall. During illumination for ophthalmic surgery, this could lead to an unintended increase in intraocular retinal irradiance, which was already discussed in previous studies but without a detailed consideration of spectral differences and a potential influence of pigmentation. In this study this effect is investigated wavelength-dependent to see if different wavelengths lead to different increase in irradiance, with a special focus on the raise in photochemical and thermal hazard to the retina. It is also examined whether this effect is dependent on the pigmentation of the eye. METHODS: The reflectance properties of either less or highly pigmented porcine eyes are measured in the wavelength range between 350 and 1100nm with an integrating sphere and a spectrometer. With these reflectance spectra the wavelength-dependent Sphere Multiplier M of porcine eyes can be calculated, which represents the increase of radiance due to multiple reflections inside a sphere compared to a planar diffuser of the same size. Based on measurements of the emitted irradiance of ophthalmic illumination fibers the increase in photochemical and thermal retinal hazard due to these multiple reflections is calculated for eyes with small and high amounts of pigmentation. RESULTS: The reflectance of the inner eyewall in the range between 350 and 1100nm is significantly higher for eyes with low pigmentation (between 4.90% and 37.44% reflectance) in comparison to eyes with a high amount of pigmentation (between 4.30% and 28.88% reflectance). The Sphere Multiplier for the inner side of the eyewall (sclera, choroid and retina) ranges between 1.13 and 1.59 and between 1.13 and 1.48 for eyes with low and high pigmentation, respectively, in the range between 350 and 1100nm. The reflectance, as well as the Sphere Multiplier, is strongly wavelength-dependent due to the absorption spectra of melanin and hemoglobin, which are located in the eye. With increasing wavelength, the reflection properties and the Sphere Multiplier also increases. With this, the photochemical retinal hazard of highly pigmented eyes increases by (14.11± 0.09)% and of lightly pigmented eyes by (16.75±0.35)% compared to if the reflection properties are not considered. The thermal retinal hazard increases by (14.30±0.07)% for highly pigmented eyes and by (19.65±0.17)% for low pigmented eyes. CONCLUSION: This study demonstrates that the anatomy and pigmentation of the eye plays an important role for the reflectance properties of the eye and for the photochemical and thermal hazard to the retina.

Determination of the intraocular irradiance and potential retinal hazards at various positions in the eye during transscleral equatorial illumination for different applied pressures.

PURPOSE: With diaphanoscopic illumination of the eye, the intensity of light entering its interior depends on the transmission properties of the eyewall. Light that passes through the eyewall can cause damage to the retina. Therefore, in this study, the intraocular irradiances are determined at different positions on the retina, directly behind the illuminated eyewall, the opposite eyewall and near the macula of ex-vivo porcine eyes. These irradiances are examined for their dependence on the pressure applied on the eyewall with the illuminating fiber and for the influence of the pigmentation of the eye. METHODS: In total 221 ex-vivo porcine eyes were investigated. For transscleral illumination an illumination fiber with a diffusing adapter cap is pressed against the equatorial eyewall. The illumination fiber is pressed onto the eye and the pressure is measured in the anterior chamber. Three different pressures are applied, 23, 78 and 132 mmHg. A detection fiber with diffusing fiber tip is inserted into the eye at the desired position. The eyes were divided in groups with high and less pigmentation to investigate the influence of the pigmentation on the intraocular irradiance. RESULTS: The intraocular irradiances Eintra increases for various increasing applied pressures with the illumination fiber on the eyewall and for various positions inside the eye. With this the irradiances weighted with the photochemical and thermal hazard weighting function, EA-R and EVIR-R, also increases. Differences in Eintra, EA-R and EVIR-R could be found for different pigmented eyes as these values are higher for less pigmented eyes than for strong pigmented ones. CONCLUSION: The hazard to the retina during diaphanoscopic illumination of the eye depends on how strong the surgeon presses the illumination fiber on the eyewall. Depending on the applied pressure and the measuring position in the eye, the specified limit for the photochemical hazard to the retina is partly exceeded. The pigmentation of the eye also plays a role. The irradiance in less pigmented eyes appears to be higher than in strongly pigmented eyes. Because of this, the surgeon should be able to adjust the intensity of the light source to the color of the patient's eye.

Sensitivity of influenza virus to ultraviolet irradiation.

Background: The measures implemented against the coronavirus pandemic also led to a sharp decline in influenza infections in the 2020/2021 flu season. In the meantime, however, the number of influenza infections has risen again; it is known from history that influenza viruses can also trigger severe pandemics. Therefore, we investigated the efficacy of ultraviolet radiation in the spectral range of 200-400 nm for inactivating influenza viruses. Materials and methods: The scientific literature was searched for published ultraviolet (UV) irradiation experiments with influenza viruses and the results were standardized by determining the lg-reduction dose. The results were then sorted and analyzed by virus type and wavelength as far as possible. Results: The scope of the published data sets was limited and revealed large variations with regard to the lg-reduction dose. Only for experiments with influenza viruses in liquid media in the UVC spectral range around 260 nm - the emission range of commonly-used mercury vapor lamps - was there sufficient data to compare virus types. No significant difference between the virus (sub-) types was observed. The lg-reduction dose in this spectral range is 1.75 mJ/cm2 (median). It was also shown that influenza viruses are particularly sensitive in the far-UVC spectral range (200-230 nm). Conclusion: UVC, including far-UVC, is suited for influenza virus inactivation as long as the viruses are in UVC-transparent materials. A large difference in the UV sensitivity of different influenza viruses from the last approx. 100 years could not be detected. Thus, it is reasonable to assume that future influenza viruses will also be similarly UV-sensitive or that UV can also inactivate new influenza viruses.

UVC, UVB and UVA susceptibility of Phi6 and its suitability as a SARS-CoV-2 surrogate.

For SARS-CoV-2 disinfection systems or applications that are based on UVC, UVB or UVA irradiation, it would be desirable to have a SARS-CoV-2 surrogate for tests and development, which does not require a laboratory with a high biosafety level. The bacteriophage Phi 6, an enveloped RNA virus like coronaviruses, is an obvious candidate for such a surrogate. In this study, UVC, UVB and UVA log-reduction doses for Phi6 are determined by plaque assay. Log-reduction doses for SARS-CoV-2 are retrieved from a literature research. Because of a high variability of the published results, median log-reduction doses are determined for defined spectral ranges and compared to Phi6 data in the same intervals. The measured Phi6 log-reduction doses for UVC (254 nm), UVB (311 nm) and UVA (365 nm) are 31.7, 980 and 14 684 mJ/cm2, respectively. The determined median log-reduction doses for SARS-CoV-2 are much lower, only about 1.7 mJ/cm2 within the spectral interval 251-270 nm. Therefore, Phi6 can be photoinactivated by all UV wavelengths but it is much less UV sensitive compared to SARS-CoV-2 in all UV spectral ranges. Thus, Phi6 is no convincing SARS-CoV-2 surrogate in UV applications.

Enhanced cellular migration and prolonged chondrogenic differentiation in decellularized cartilage scaffolds under dynamic culture conditions.

Lesions of aural, nasal and tracheal cartilage are frequently reconstructed by complex surgeries which are based on harvesting autologous cartilage from other locations such as the rib. Cartilage tissue engineering (CTE) is regarded as a promising alternative to attain vital cartilage. Nevertheless, CTE with nearly natural properties poses a significant challenge to research due to the complex reciprocal interactions between cells and extracellular matrix which have to be imitated and which are still not fully understood. Thus, we used a custom-made glass bioreactor to enhance cell migration into decellularized porcine cartilage scaffolds (DECM) and mimic physiological conditions. The DECM seeded with human nasal chondrocytes (HPCH) were cultured in the glass reactor for 6 weeks and examined by histological and immunohistochemical staining, biochemical analyses and real time-PCR at 14, 28 and 42 days. The migration depth and the number of migrated cells were quantified by computational analysis. Compared to the static cultivation, the dynamic culture (DC) fostered migration of HPCH into deeper tissue layers. Furthermore, cultivation in the bioreactor enhanced differentiation of the cells during the first 14 days, but differentiation diminished in the course of further cultivation. We consider the DC in the presented bioreactor as a promising tool to facilitate CTE and to help to better understand the complex physiological processes during cartilage regeneration. Maintaining differentiation of chondrocytes and improving cellular migration by further optimizing culture conditions is an important prerequisite for future clinical application.