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Manstein D, Chan HH, Bhawalkar J, Erenburg I, Pomerantz H, Escobar J, Tannous Z, Yoo J, Tran TN, Katkam R, Anderson RR. Focal point technology: Controlling treatment depth and pattern of skin injury by a novel highly focused laser. J Am Acad Dermatol 2024:S0190-9622(24)02809-3. [PMID: 39251027 DOI: 10.1016/j.jaad.2024.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2024] [Revised: 08/11/2024] [Accepted: 09/01/2024] [Indexed: 09/11/2024]
Abstract
BACKGROUND Selective photothermolysis has limitations in efficacy and safety for dermal targets. We describe a novel concept using scanned focused laser microbeams for precise control of dermal depth and pattern of injury, using a 1550 nm laser that generates an array of conical thermal zones while minimizing injury to the epidermis. OBJECTIVE To characterize the conical thermal zones in vivo and determine safe starting parameters to transition to a second phase to explore potential clinical indications. METHODS A focused toroidal (ring) laser beam was delivered through a cold sapphire window, sparing epidermal injury in a central zone. Pulse energy, lesion depth, density, and energy delivery were titrated in ex vivo human skin and subsequently on the backs of 21 human subjects. RESULTS Histology showed microscale patterns of thermal injury, which varied predictably with laser parameters. Time-course healing through histology and skin surface imaging demonstrated the ability of the device to deliver high energies without sequelae. LIMITATIONS Clinical data are currently being collected to further explore the safety and efficacy of the device. CONCLUSION The 1550 nm laser with focal point technology enables precise control of lesion depth while simultaneously sparing a large portion of the epidermis, lowering the risk of adverse effects.
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Dos Anjos C, Wang Y, Truong-Bolduc QC, Bolduc PK, Liu M, Hooper DC, Anderson RR, Dai T, Leanse LG. Blue Light Compromises Bacterial β-Lactamases Activity to Overcome β-Lactam Resistance. Lasers Surg Med 2024; 56:673-681. [PMID: 39039622 DOI: 10.1002/lsm.23819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 05/03/2024] [Accepted: 06/10/2024] [Indexed: 07/24/2024]
Abstract
OBJECTIVE In this study, we evaluated the effectiveness of antimicrobial blue light (aBL; 410 nm wavelength) against β-lactamase-carrying bacteria and the effect of aBL on the activity of β-lactamases. METHODS Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae strains carrying β-lactamases as well as a purified β-lactamase enzymes were studied. β-lactamase activity was assessed using a chromogenic cephalosporin hydrolysis assay. Additionally, we evaluated the role of porphyrins in the photoreaction, as well as protein degradation by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Finally, we investigated the bactericidal effect of combined aBL-ceftazidime exposure against a metallo-β-lactamase expressing P. aeruginosa strain. RESULTS Our study demonstrated that aBL effectively killed β-lactamase-producing bacteria and reduced β-lactamase activity. After an aBL exposure of 1.52 J/cm2, a 50% reduction in enzymatic activity was observed in P. aeruginosa. Additionally, we found a 40% decrease in the photoreaction activity of porphyrins following an aBL exposure of 64.8 J/cm2. We also revealed that aBL reduced β-lactamase activity via protein degradation (after 136.4 J/cm2). Additionally, aBL markedly improved the bactericidal effect of ceftazidime (by >4-log10) in the metallo-β-lactamase P. aeruginosa strain. CONCLUSION Our results provide evidence that aBL compromises bacterial β-lactamase activity, offering a potential approach to overcome β-lactam resistance in bacteria.
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Herringshaw E, Turk C, Korupolu S, Tagar Sar-El M, Anderson RR, Levin Y, Tam J. A practical device to produce consistent, controlled cryoinjury on the skin. Cryobiology 2024; 116:104951. [PMID: 39128508 DOI: 10.1016/j.cryobiol.2024.104951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Revised: 08/06/2024] [Accepted: 08/08/2024] [Indexed: 08/13/2024]
Abstract
It has long been known that sensitivity to cold-induced damage can vary greatly between different cell types, with lethal temperatures reportedly ranging from -2 °C for canine osteocytes, to -70 °C for mammary adenocarcinomas. This suggests that, for certain applications, "therapeutic windows" may exist wherein the cryosurgery temperature could be controlled to specifically target more cold-sensitive cell types, while sparing less sensitive cells. However, this potential selectivity has not been developed into practical clinical treatments, in part because of a lack of available investigative tools that can provide consistent, reproducible cooling within the desired temperature range. Here we describe an experimental cryosurgery tool that allows user control over the three key cryosurgery parameters - temperature, pressure, and duration. The tool is composed of inexpensive components that are generally accessible in most laboratory settings, and could be a practical investigative tool for developing and optimizing novel topical cryosurgery approaches.
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Fuchs C, Wang Y, Wise E, Farinelli WA, Anderson RR, Cho S, Meyerle JH, Tam J. Structural and molecular characteristics of weight-bearing volar skin can be reconstituted by micro skin tissue column grafting. FASEB J 2024; 38:e23873. [PMID: 39105468 DOI: 10.1096/fj.202400866r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 07/08/2024] [Accepted: 07/26/2024] [Indexed: 08/07/2024]
Abstract
For patients with lower limb amputations, prostheses are immensely helpful for mobility and the ability to perform job-related or recreational activities. However, the skin covering the amputation stump is typically transposed from adjacent areas of the leg and lacks the weight-bearing capacity that is only found in the specialized skin covering the palms and soles (a.k.a. volar skin). As a result, the skin tissue in direct contact with the prosthesis frequently breaks down, leading to the development of painful sores and other complications that limit, and often preclude, the use of prostheses. Transplanting volar skin onto amputation stumps could be a solution to these problems, but traditional skin transplantation techniques cause substantial morbidity at the donor site, such as pain and scarring, which are especially problematic for volar skin given the critical functional importance of the volar skin areas. We previously developed the technology to collect and engraft full-thickness skin tissue while avoiding long-term donor site morbidity, by harvesting the skin in the form of small (~0.5 mm diameter) cores that we termed "micro skin tissue columns" (MSTCs), so that each donor wound is small enough to heal quickly and without clinically appreciable scarring or other long-term abnormalities. The goal of this study was to establish whether a similar approach could be used to confer the structural and molecular characteristics of volar skin ectopically to other skin areas. In a human-to-mouse xenograft model, we show the long-term persistence of various human plantar MSTC-derived cell types in the murine recipient. Then in an autologous porcine model, we harvested MSTCs from the bottom of the foot and transplanted them onto excision wounds on the animals' trunks. The healing processes at both the donor and graft sites were monitored over 8 weeks, and tissue samples were taken to verify volar-specific characteristics by histology and immunohistochemistry. The volar donor sites were well-tolerated, healed rapidly, and showed no signs of scarring or any other long-term defects. The graft sites were able to maintain volar-specific histologic features and expression of characteristics protein markers, up to the 8-week duration of this study. These results suggest that MSTC grafting could be a practical approach to obtain autologous donor volar skin tissue, confer volar skin characteristics ectopically to nonvolar skin areas, improve the load-bearing capacity of amputation stump skin, and ultimately enhance mobility and quality-of-life for lower limb amputees.
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Leaker BD, Wang Y, Tam J, Anderson RR. Analysis of culture and RNA isolation methods for precision-cut liver slices from cirrhotic rats. Sci Rep 2024; 14:15349. [PMID: 38961190 PMCID: PMC11222550 DOI: 10.1038/s41598-024-66235-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 06/28/2024] [Indexed: 07/05/2024] Open
Abstract
Precision-cut liver slices (PCLS) are increasingly used as a model to investigate anti-fibrotic therapies. However, many studies use PCLS from healthy animals treated with pro-fibrotic stimuli in culture, which reflects only the early stages of fibrosis. The effects of different culture conditions on PCLS from cirrhotic animals has not been well characterized and there is no consensus on optimal methods. In this study, we report a method for the collection and culture of cirrhotic PCLS and compare the effect of common culture conditions on viability, function, and gene expression. Additionally, we compared three methods of RNA isolation and identified a protocol with high yield and purity. We observed significantly increased albumin production when cultured with insulin-transferrin-selenium and dexamethasone, and when incubated on a rocking platform. Culturing with insulin-transferrin-selenium and dexamethasone maintained gene expression closer to the levels in fresh slices. However, despite stable viability and function up to 4 days, we found significant changes in expression of key genes by day 2. Interestingly, we also observed that cirrhotic PCLS maintain viability in culture longer than slices from healthy animals. Due to the influence of matrix stiffness on fibrosis and hepatocellular function, it is important to evaluate prospective anti-fibrotic therapies in a platform that preserves tissue biomechanics. PCLS from cirrhotic animals represent a promising tool for the development of treatments for chronic liver disease.
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Ortiz AE, Ahluwalia J, Anderson RR, Franco W, Brian Jiang SI. Autofluorescence Excitation Imaging of Nonmelanoma Skin Cancer for Margin Assessment Before Mohs Micrographic Surgery: A Pilot Study. Dermatol Surg 2024; 50:616-619. [PMID: 38518178 DOI: 10.1097/dss.0000000000004171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2024]
Abstract
BACKGROUND Autofluorescence photography can detect specific light-tissue interactions and record important pathophysiological changes associated with nonmelanoma skin cancer (NMSC), which has been ascribed to the fluorescence of an aromatic amino acid, tryptophan. OBJECTIVE To assess the impact of a novel, autofluorescence imaging (AFI) device on margin control for NMSCs before Mohs micrographic surgery (MMS) in an effort to decrease overall operating time. METHODS Before the initial stage of MMS, NMSCs were measured with a 2-mm margin as standard of care (normal margin). The tumor was then imaged with the AFI device. A 2-mm margin was drawn around the fluorescent area captured by the AFI device and was referred to as the camera margin. The tumor was excised based on the normal margin and evaluated on frozen histological section. RESULTS Imaging based on the AFI device resulted in appropriate recommendations for margin control in 8 of 11 tumors. Four of these tumors did not fluoresce and demonstrated a lack of tumor residuum on stage I specimen, as anticipated. There were no side effects from the AFI device. CONCLUSION This is an initial pilot study that supports the use of a novel, noninvasive imaging device to help with margin assessment before MMS. On optimization, this device has potential to extend applicability to surgical excisions for tumors that do not fulfill criteria for MMS.
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Fuchs C, Stalnaker KJ, Dalgard CL, Sukumar G, Hupalo D, Dreyfuss JM, Pan H, Wang Y, Pham L, Wu X, Jozic I, Anderson RR, Cho S, Meyerle JH, Tam J. Plantar Skin Exhibits Altered Physiology, Constitutive Activation of Wound-Associated Phenotypes, and Inherently Delayed Healing. J Invest Dermatol 2024; 144:1633-1648.e14. [PMID: 38237729 DOI: 10.1016/j.jid.2023.12.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 12/16/2023] [Accepted: 12/19/2023] [Indexed: 06/24/2024]
Abstract
Wound research has typically been performed without regard for where the wounds are located on the body, despite well-known heterogeneities in physical and biological properties between different skin areas. The skin covering the palms and soles is highly specialized, and plantar ulcers are one of the most challenging and costly wound types to manage. Using primarily the porcine model, we show that plantar skin is molecularly and functionally more distinct from nonplantar skin than previously recognized, with unique gene and protein expression profiles, broad alterations in cellular functions, constitutive activation of many wound-associated phenotypes, and inherently delayed healing. This unusual physiology is likely to play a significant but underappreciated role in the pathogenesis of plantar ulcers as well as the last 25+ years of futility in therapy development efforts. By revealing this critical yet unrecognized pitfall, we hope to contribute to the development of more effective therapies for these devastating nonhealing wounds.
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Wang Y, Herringshaw E, Anderson RR, Tam J. The Yucatan miniature swine as a model for post-inflammatory hyperpigmentation. Pigment Cell Melanoma Res 2024; 37:403-410. [PMID: 38361478 DOI: 10.1111/pcmr.13162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 12/15/2023] [Accepted: 01/09/2024] [Indexed: 02/17/2024]
Abstract
Post-inflammatory hyperpigmentation (PIH) is a hypermelanosis that often occurs secondary to skin irritation or injury, especially in darker skin tones, for which there is currently a lack of effective treatment options. Few preclinical models are available to study PIH. Here, we show that the Yucatan miniature pig consistently develops PIH after skin injuries. Skin wounds were produced on Yucatan pigs by needle punches, full-thickness excisions, or burns. Wound sites were monitored and photographed regularly. Tissue samples were collected after 24 weeks and processed for histology/immunohistochemistry. Skin pigmentation and histologic changes were quantified by computer-assisted image analyses. All injury methods resulted in hyperpigmentation. Melanin content at the histologic level was quantified in the larger (burn and excision) wounds, showing a significant increase compared to uninjured skin. Increased melanin was found for both epidermal and dermal regions. Dermal melanin deposits were primarily clustered around the papillary vasculature, and were associated not with melanocytes but with leukocytes. The Yucatan miniature pig model recapitulates key clinical and histologic features of PIH in humans, including skin hyperpigmentation at both gross and histologic levels, and persistence of dermal melanin subsequent to injury. This model could be used to further our understanding of the etiology of PIH, and for new therapy development.
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Leaker BD, Sojoodi M, Tanabe KK, Popov YV, Tam J, Anderson RR. Increased susceptibility to ischemia causes exacerbated response to microinjuries in the cirrhotic liver. FASEB J 2024; 38:e23585. [PMID: 38661043 DOI: 10.1096/fj.202301438rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 03/07/2024] [Accepted: 03/18/2024] [Indexed: 04/26/2024]
Abstract
Fractional laser ablation is a technique developed in dermatology to induce remodeling of skin scars by creating a dense pattern of microinjuries. Despite remarkable clinical results, this technique has yet to be tested for scars in other tissues. As a first step toward determining the suitability of this technique, we aimed to (1) characterize the response to microinjuries in the healthy and cirrhotic liver, and (2) determine the underlying cause for any differences in response. Healthy and cirrhotic rats were treated with a fractional laser then euthanized from 0 h up to 14 days after treatment. Differential expression was assessed using RNAseq with a difference-in-differences model. Spatial maps of tissue oxygenation were acquired with hyperspectral imaging and disruptions in blood supply were assessed with tomato lectin perfusion. Healthy rats showed little damage beyond the initial microinjury and healed completely by 7 days without scarring. In cirrhotic rats, hepatocytes surrounding microinjury sites died 4-6 h after ablation, resulting in enlarged and heterogeneous zones of cell death. Hepatocytes near blood vessels were spared, particularly near the highly vascularized septa. Gene sets related to ischemia and angiogenesis were enriched at 4 h. Laser-treated regions had reduced oxygen saturation and broadly disrupted perfusion of nodule microvasculature, which matched the zones of cell death. Our results demonstrate that the cirrhotic liver has an exacerbated response to microinjuries and increased susceptibility to ischemia from microvascular damage, likely related to the vascular derangements that occur during cirrhosis development. Modifications to the fractional laser tool, such as using a femtosecond laser or reducing the spot size, may be able to prevent large disruptions of perfusion and enable further development of a laser-induced microinjury treatment for cirrhosis.
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Richey P, Funk M, Sakamoto F, Plotkin S, Ly I, Jordan J, Muzikansky A, Roberts J, Farinelli W, Levin Y, Garibyan L, Blakeley JO, Anderson RR. Noninvasive treatment of cutaneous neurofibromas (cNFs): Results of a randomized prospective, direct comparison of four methods. J Am Acad Dermatol 2024; 90:767-774. [PMID: 38086517 DOI: 10.1016/j.jaad.2023.11.058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 10/20/2023] [Accepted: 11/13/2023] [Indexed: 01/09/2024]
Abstract
BACKGROUND People with Neurofibromatosis Type 1 (NF1) suffer disfigurement and pain when hundreds to thousands of cutaneous neurofibromas (cNFs) appear and grow throughout life. Surgical removal of cNFs under anesthesia is the only standard therapy, leaving surgical scars. OBJECTIVE Effective, minimally-invasive, safe, rapid, tolerable treatment(s) of small cNFs that may prevent tumor progression. METHODS Safety, tolerability, and efficacy of 4 different treatments were compared in 309, 2-4 mm cNFs across 19 adults with Fitzpatrick skin types (FST) I-IV: radiofrequency (RF) needle coagulation, 755 nm alexandrite laser with suction, 980 nm diode laser, and intratumoral injection of 10 mg/mL deoxycholate. Regional pain, clinical responses, tumor height and volume (by 3D photography) were assessed before, 3 and 6 months post-treatment. Biopsies were obtained electively at 3 months. RESULTS There was no scarring or adverse events > grade 2. Each modality significantly (P < .05) reduced or cleared cNFs, with large variation between tumors and participants. Alexandrite laser and deoxycholate were fast and least painful; 980 nm laser was most painful. Growth of cNFs was not stimulated by treatment(s) based on height and volume values at 3 and 6 months compared to baseline. LIMITATIONS Intervention was a single treatment session; dosimetry has not been optimized. CONCLUSIONS Small cNFs can be rapidly and safely treated without surgery.
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Leanse LG, dos Anjos C, Kaler KR, Hui J, Boyd JM, Hooper DC, Anderson RR, Dai T. Blue Light Potentiates Antibiotics in Bacteria via Parallel Pathways of Hydroxyl Radical Production and Enhanced Antibiotic Uptake. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303731. [PMID: 37946633 PMCID: PMC10754126 DOI: 10.1002/advs.202303731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 09/13/2023] [Indexed: 11/12/2023]
Abstract
In the age of antimicrobial resistance, the urgency by which novel therapeutic approaches need to be introduced into the clinical pipeline has reached critical levels. Antimicrobial blue light (aBL), as an alternative approach, has demonstrated promise as a stand-alone therapeutic method, albeit with a limited window of antimicrobial activity. Work by others indicates that treatment with antibiotics increases the production of reactive oxygen species (ROS) which may, in part, contribute to the bactericidal effects of antibiotics. These findings suggest that there may be potential for synergistic interactions with aBL, that similarly generates ROS. Therefore, in this study, the mechanism of aBL is investigated, and the potential for aBL to synergistically promote antibiotic activity is similarly evaluated. Furthermore, the translatability of using aBL and chloramphenicol in combination within a mouse model of Acinetobacter baumanii burn infection is assessed. It is concluded that porphyrins and hydroxyl radicals driven by "free iron" are paramount to the effectiveness of aBL; and aBL is effective at promoting multiple antibiotics in different multidrug-resistant bacteria. Moreover, rROS up-regulation, and promoted antibiotic uptake are observed during aBL+antibiotic exposure. Lastly, aBL combined with chloramphenicol appears to be both effective and safe for the treatment of A. baumannii burn infection. In conclusion, aBL may be a useful adjunct therapy to antibiotics to potentiate their action.
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Moradi Tuchayi S, Khachatryan Y, Wang Y, Rox Anderson R, Wang JS, Wein MN, Garibyan L. Selective reduction of visceral adipose tissue with injectable ice slurry. Sci Rep 2023; 13:16350. [PMID: 37770553 PMCID: PMC10539385 DOI: 10.1038/s41598-023-43220-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 09/21/2023] [Indexed: 09/30/2023] Open
Abstract
Reduction in visceral adipose tissue (VAT) mass reduces body weight and metabolic disease risk in obese patients. However surgical removal of VAT is highly invasive and thus not clinically feasible. We developed an injectable ice slurry for selective reduction of adipose tissue through cryolipolysis. The aim of this study was to investigate safety, feasibility and mechanism of ice slurry-induced cryolipolysis of VAT. Perigonadal VAT in diet-induced obese mice and rats was subjected to slurry or sham treatment. Body weight and blood chemistry were monitored for 56 days post-treatment. Histological analysis and molecular studies were performed to elucidate mechanisms of fat reduction. Treatment of VAT was well tolerated in all animals. Slurry induced adipocyte cell death via selective cryolipolysis; significant weight loss was noted at day 21 post-treatment. RNA sequencing from treated VAT samples showed increased expression of genes involved in inflammation, immune response, collagen biosynthesis and wound healing, and decreased expression of adipokines. This study demonstrates that slurry treatment is safe and effective in inducing cryolipolysis of VAT and subsequent weight loss in mice. Ice slurry is promising as a minimally-invasive treatment to reduce visceral adipose tissue.
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Negri LB, Mannaa Y, Korupolu S, Farinelli WA, Anderson RR, Gelfand JA. Vitamin K3 (Menadione) is a multifunctional microbicide acting as a photosensitizer and synergizing with blue light to kill drug-resistant bacteria in biofilms. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2023; 244:112720. [PMID: 37186990 DOI: 10.1016/j.jphotobiol.2023.112720] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 04/10/2023] [Accepted: 05/03/2023] [Indexed: 05/17/2023]
Abstract
Cutaneous bacterial wound infections typically involve gram-positive cocci such as Staphylococcus aureus (SA) and usually become biofilm infections. Bacteria in biofilms may be 100-1000-fold more resistant to an antibiotic than the clinical laboratory minimal inhibitory concentration (MIC) for that antibiotic, contributing to antimicrobial resistance (AMR). AMR is a growing global threat to humanity. One pathogen-antibiotic resistant combination, methicillin-resistant SA (MRSA) caused more deaths globally than any other such combination in a recent worldwide statistical review. Many wound infections are accessible to light. Antimicrobial phototherapy, and particularly antimicrobial blue light therapy (aBL) is an innovative non-antibiotic approach often overlooked as a possible alternative or adjunctive therapy to reduce antibiotic use. We therefore focused on aBL treatment of biofilm infections, especially MRSA, focusing on in vitro and ex vivo porcine skin models of bacterial biofilm infections. Since aBL is microbicidal through the generation of reactive oxygen species (ROS), we hypothesized that menadione (Vitamin K3), a multifunctional ROS generator, might enhance aBL. Our studies suggest that menadione can synergize with aBL to increase both ROS and microbicidal effects, acting as a photosensitizer as well as an ROS recycler in the treatment of biofilm infections. Vitamin K3/menadione has been given orally and intravenously worldwide to thousands of patients. We conclude that menadione/Vitamin K3 can be used as an adjunct to antimicrobial blue light therapy, increasing the effectiveness of this modality in the treatment of biofilm infections, thereby presenting a potential alternative to antibiotic therapy, to which biofilm infections are so resistant.
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Goulopoulos A, Etim E, Korupolu S, Farinelli W, Sierra H, Anderson RR, Fischbach A, Franco W. Optical, flow, and thermal analysis of a phototherapy extracorporeal membrane oxygenator for treating carbon monoxide poisoning. Lasers Surg Med 2023; 55:390-404. [PMID: 36883985 DOI: 10.1002/lsm.23649] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 02/09/2023] [Accepted: 02/23/2023] [Indexed: 03/09/2023]
Abstract
BACKGROUND Extracorporeal membrane oxygenators (ECMO) are currently utilized to mechanically ventilate blood when lung or lung and heart function are impaired, like in cases of acute respiratory distress syndrome (ARDS). ARDS can be caused by severe cases of carbon monoxide (CO) inhalation, which is the leading cause of poison-related deaths in the United States. ECMOs can be further optimized for severe CO inhalation using visible light to photo-dissociate CO from hemoglobin (Hb). In previous studies, we combined phototherapy with an ECMO to design a photo-ECMO device, which significantly increased CO elimination and improved survival in CO-poisoned animal models using light at 460, 523, and 620 nm wavelengths. Light at 620 nm was the most effective in removing CO. OBJECTIVE The aim of this study is to analyze the light propagation at 460, 523, and 620 nm wavelengths and the 3D blood flow and heating distribution within the photo-ECMO device that increased CO elimination in CO-poisoned animal models. METHODS Light propagation, blood flow dynamics, and heat diffusion were modeled using the Monte Carlo method and the laminar Navier-Stokes and heat diffusion equations, respectively. RESULTS Light at 620 nm propagated through the device blood compartment (4 mm), while light at 460 and 523 nm only penetrated 48% to 50% (~2 mm). The blood flow velocity in the blood compartment varied with regions of high (5 mm/s) and low (1 mm/s) velocity, including stagnant flow. The blood temperatures at the device outlet for 460, 523, and 620 nm wavelengths were approximately 26.7°C, 27.4°C, and 20°C, respectively. However, the maximum temperatures within the blood treatment compartment rose to approximately 71°C, 77°C, and 21°C, respectively. CONCLUSIONS As the extent of light propagation correlates with efficiency in photodissociation, the light at 620 nm is the optimal wavelength for removing CO from Hb while maintaining blood temperatures below thermal damage. Measuring the inlet and outlet blood temperatures is not enough to avoid unintentional thermal damage by light irradiation. Computational models can help eliminate risks of excessive heating and improve device development by analyzing design modifications that improve blood flow, like suppressing stagnant flow, further increasing the rate of CO elimination.
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Stalnaker KJ, Fuchs C, Slate A, Camacho JN, Pham L, Wang Y, Anderson RR, Tam J. Boot camp: Training and dressing regimens for modeling plantar wounds in the swine. Lab Anim 2023; 57:59-68. [PMID: 35962527 DOI: 10.1177/00236772221111058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Foot ulceration annually affects millions of patients and accounts for billions of dollars in medical expenses in the US alone. Many previous studies have investigated co-morbidities associated with impaired healing, such as microbial infection, compromised circulation, and diabetes. By comparison, little is known about how wound healing proceeds in plantar skin, despite its many unique specializations related to its load-bearing function. One of the main challenges in modeling plantar wounds is the difficulty in maintaining wound dressings, as animals generally have a low tolerance to wearing bandages on their feet. With assistance from the MGH Center for Comparative Medicine, we developed a positive reinforcement-based behavioral training regimen that successfully induced tolerance for plantar dressings in swine, which is a critical first step towards enabling in vivo study of the wound healing process in this highly specialized skin area. This training program will be described in detail in this manuscript.
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Moradi Tuchayi S, Wang Y, Khodorova A, Pence IJ, Evans CL, Anderson RR, Lerner EA, Woolf CJ, Garibyan L. Cryoneurolysis with Injectable Ice Slurry Modulates Mechanical Skin Pain. J Invest Dermatol 2023; 143:134-141.e1. [PMID: 35985498 DOI: 10.1016/j.jid.2022.07.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 06/30/2022] [Accepted: 07/21/2022] [Indexed: 11/16/2022]
Abstract
Cutaneous pain is a common symptom of skin disease, and available therapies are inadequate. We developed a neural selective and injectable method of cryoneurolysis with ice slurry, which leads to a long-lasting decrease in mechanical pain. The aim of this study is to determine whether slurry injection reduces cutaneous pain without inducing the side effects associated with conventional cryoneurolysis. Using the rat sciatic nerve, we examined the effects of slurry on nerve structure and function in comparison with the effects of a Food and Drug Administration‒approved cryoneurolysis device (Iovera). Coherent anti-Stokes Raman scattering microscopy and immunofluorescence staining were used to investigate histological effects on the sciatic nerve and on downstream cutaneous nerve fibers. Complete Freund's Adjuvant model of cutaneous pain was used to study the effect of the slurry on reducing pain. Structural changes in myelin induced by slurry were comparable with those induced by Iovera, which uses much colder temperatures. Compared with that of Iovera, the decrease in mechanical pain due to slurry was less profound but lasted longer without signs of dysesthesia. Slurry did not cause a reduction of epidermal nerve fibers or a change in thermal pain sensitivity. Slurry-treated rats showed reduced cutaneous mechanical pain in response to Complete Freund's Adjuvant. Slurry injection can be used to successfully reduce cutaneous pain without causing dysesthesia.
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Ni P, Farinelli WA, Cheng LL, Farrar CT, Motamarry A, Moradi Tuchayi S, Wang Y, Anderson RR, Garibyan L. Total ice content and lipid saturation determine adipose tissue cryolipolysis by injection of ice-slurry. Lasers Surg Med 2023; 55:116-125. [PMID: 35598082 PMCID: PMC9676409 DOI: 10.1002/lsm.23557] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/30/2022] [Accepted: 05/03/2022] [Indexed: 02/04/2023]
Abstract
OBJECTIVES Cryolipolysis uses tissue cooling to solidify lipids, preferentially damaging lipid-rich cells. Topical cooling is popular for the reduction of local subcutaneous fat. Injection of biocompatible ice-slurry is a recently introduced alternative. We developed and verified a quantitative model that simulates the heat exchange and phase changes involved, offering insights into ice-slurry injection for treating subcutaneous fat. METHODS Finite element method was used to model the spatial and temporal progression of heat transfer between adipose tissue and injected ice-slurry, estimating dose-response relationships between properties of the slurry and size of tissue affected by cryolipolysis. Phase changes of both slurry and adipose tissue lipids were considered. An in vivo swine model was used to validate the numerical solutions. Oils with different lipid compositions were exposed to ice-slurry in vitro to evaluate the effects of lipid freezing temperature. Microscopy and nuclear magnetic resonance (NMR) were performed to detect lipid phase changes. RESULTS A ball of granular ice was deposited at the injection site in subcutaneous fat. Total injected ice content determines both the effective cooling region of tissue, and the duration of tissue cooling. Water's high latent heat of fusion enables tissue cooling long after slurry injection. Slurry temperature affects the rate of tissue cooling. In swine, when 30 ml slurry injection at -3.5°C was compared to 15 ml slurry injection at -4.8°C (both with the same total ice content), the latter led to almost twice faster tissue cooling. NMR showed a large decrease in diffusion upon lipid crystallization; saturated lipids with higher freezing temperatures were more susceptible to solidification after ice-slurry injection. CONCLUSIONS Total injected ice content determines both the volume of tissue treated by cryolipolysis and the cooling duration after slurry injection, while slurry temperature affects the cooling rate. Lipid saturation, which varies with diet and anatomic location, also has an important influence.
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Wilson BN, Shah R, Menzer C, Aleisa A, Sun MD, Kwong BY, Kaffenberger BH, Seminario-Vidal L, Barker CA, Stubblefield MD, Romesser PB, Fabbrocini G, Alam M, Abdulla F, Dulmage B, Sibaud V, Anadkat M, Mazer JM, Parikh D, McLellan B, Cartier H, Pugliese S, Wolkerstorfer A, Laubach HJ, LeBoeuf N, Leventhal J, Wan DC, Choi J, Tran TN, Anderson RR, Markova A, Rossi A. Consensus on the clinical management of chronic radiation dermatitis and radiation fibrosis: a Delphi survey. Br J Dermatol 2022; 187:1054-1056. [PMID: 36047980 PMCID: PMC10087782 DOI: 10.1111/bjd.21852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 08/22/2022] [Accepted: 08/30/2022] [Indexed: 12/24/2022]
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Wenande E, Chandra Gundavarapu S, Tam J, Bhayana B, Thomas CN, Farinelli WA, Vakoc BJ, Rox Anderson R, Haedersdal M. Local vasoregulative interventions impact drug concentrations in the skin after topical laser-assisted delivery. Lasers Surg Med 2022; 54:1288-1297. [PMID: 35593006 PMCID: PMC9675883 DOI: 10.1002/lsm.23558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/09/2022] [Accepted: 05/09/2022] [Indexed: 12/30/2022]
Abstract
INTRODUCTION The ability of ablative fractional lasers (AFL) to enhance topical drug uptake is well established. After AFL delivery, however, drug clearance by local vasculature is poorly understood. Modifications in vascular clearance may enhance AFL-assisted drug concentrations and prolong drug dwell time in the skin. Aiming to assess the role and modifiability of vascular clearance after AFL-assisted delivery, this study examined the impact of vasoregulative interventions on AFL-assisted 5-fluorouracil (5-FU) concentrations in in vivo skin. METHODS 5-FU uptake was assessed in intact and AFL-exposed skin in a live pig model. After fractional CO2 laser exposure (15 mJ/microbeam, 5% density), vasoregulative intervention using topical brimonidine cream, epinephrine solution, or pulsed dye laser (PDL) was performed in designated treatment areas, followed by a single 5% 5-FU cream application. At 0, 1, 4, 48, and 72 h, 5-FU concentrations were measured in 500 and 1500 μm skin layers by mass spectrometry (n = 6). A supplemental assessment of blood flow following AFL ± vasoregulation was performed using optical coherence tomography (OCT) in a human volunteer. RESULTS Compared to intact skin, AFL facilitated a prompt peak in 5-FU delivery that remained elevated up to 4 hours (1500 μm: 1.5 vs. 31.8 ng/ml [1 hour, p = 0.002]; 5.3 vs. 14.5 ng/ml [4 hours, p = 0.039]). However, AFL's impact was transient, with 5-FU concentrations comparable to intact skin at later time points. Overall, vasoregulative intervention with brimonidine or PDL led to significantly higher peak 5-FU concentrations, prolonging the drug's dwell time in the skin versus AFL delivery alone. As such, brimonidine and PDL led to twofold higher 5-FU concentrations than AFL alone in both skin layers by 1 hour (e.g., 500 μm: 107 ng/ml [brimonidine]; 96.9 ng/ml [PDL], 46.6 ng/ml [AFL alone], p ≤ 0.024), and remained significantly elevated at 4 hours (p ≤ 0.024). A similar pattern was observed for epinephrine, although trends remained nonsignificant (p ≥ 0.09). Prolonged 5-FU delivery was provided by PDL, resulting in sustained drug deposition compared to AFL alone at both 48 and 72 hours in the superficial skin layer (p ≤ 0.024). Supporting drug delivery findings, OCT revealed that increases in local blood flow after AFL were mitigated in test areas also exposed to PDL, brimonidine, or epinephrine, with PDL providing the greatest, sustained reduction in flow over 48 hours. CONCLUSION Vasoregulative intervention in conjunction with AFL-assisted delivery enhances and prolongs 5-FU deposition in in vivo skin.
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Orestes MI, Tuchayi SM, Wang Y, Farinelli W, Arkun K, Anderson RR, Thomas R, Garibyan L. Safety and feasibility of selective tongue fat reduction with injected ice-slurry. Laryngoscope Investig Otolaryngol 2022; 7:1675-1680. [PMID: 36258870 PMCID: PMC9575057 DOI: 10.1002/lio2.902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 07/21/2022] [Accepted: 07/23/2022] [Indexed: 11/26/2022] Open
Abstract
Objectives There is growing evidence that excess adipose tissue within the head and neck contributes to obstructive sleep apnea (OSA), particularly in obese patients. This subset of the population is often difficult to treat with surgical therapies. We theorized that a novel, transcervical method of injectable cryoablation using ice-slurry can achieve low temperatures without causing neurovascular damage or airway distress in a swine model. Methods Four Yorkshire pigs were injected with ice-slurry comprised of normal saline and 10% glycerol cooled to -6°C via a transcervical, ultrasound guided approach. Direct laryngoscopy was used to confirm accurate placement of the slurry. Thermocouple placement at the needle-tip was used to measure temperatures at injection site. Swine were monitored for clinical signs of tongue necrosis and airway edema for 2 months, and then euthanized. Twelve biopsy samples from the base of the tongue were collected for histology. These were assessed for presence of tissue damage, inflammation and collagen formation by a blinded board-certified pathologist. Results Tongue tissue temperature below 10°C was achieved for 13.5 ± 1.1 min. Minimum tissue temperature was -4 ± 0.6°C. There was no clinical or pathological evidence of tongue damage to include damage to the lingual nerve or artery. There was some histologic evidence of new collagen formation in areas of the tongue. Conclusions Transcervical ultrasound-guided ice-slurry injection is feasible, well-tolerated at temperatures previously shown to be capable of selectively targeting adipose tissue in the base of the tongue in a preclinical swine model, without causing neurovascular damage or airway distress when properly injected.
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Moradi Tuchayi S, Wang Y, Pence IJ, Fast A, Stemmer-Rachamimov A, Evans CL, Anderson RR, Garibyan L. Full Recovery after Multiple Treatments with Injectable Ice Slurry. J Pain Res 2022; 15:2905-2910. [PMID: 36132994 PMCID: PMC9482954 DOI: 10.2147/jpr.s373421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 08/20/2022] [Indexed: 12/04/2022] Open
Abstract
Background Cryoneurolysis uses tissue cooling as an opioid-sparing, long-lasting treatment for peripheral nerve pain. A nerve-selective method for cryoneurolysis by local injection of ice-slurry was developed to allow cryoneurolysis to be performed with a standard needle and syringe, similar to peripheral nerve blocks. Since the treatment of patients with chronic pain may require repeated injections, we investigated the safety and tolerance of repeated treatments in a rat model. Methods Three repeated ice-slurry treatments, given 6 weeks apart were performed around the rat sciatic nerve. Nerve and surrounding tissues were collected up to 4 months after the third treatment for analysis. Coherent anti-Stokes Raman scattering (CARS) microscopy was used to study effects on myelin sheaths and axon structure. Immunofluorescence (IF) staining was used to study effects on axon density. Hematoxylin and Eosin (H&E) staining was used to examine histologic effects on sciatic nerve and surrounding tissue. Results Histologic and CARS image analysis of nerve tissue collected months after three injections demonstrated recovery of nerve structure, myelin organization and axon density to baseline levels, without any residual inflammation, scarring or neuroma formation. No inflammation or scarring was detected in surrounding skin and muscle tissues. Conclusion Repeated ice-slurry injections cause temporary, nerve-selective and reversible changes in the peripheral nerve. There was no histologic damage to surrounding skin and muscle tissues. Repeated treatments with injectable ice-slurry for cryoneurolysis appear to be safe and well tolerated. Clinical studies for patients with chronic pain are warranted.
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Wat H, Kawa NI, Anderson RR, Avram MM. Precise volumetric quantification using 3D stereophotogrammetry in procedural and surgical dermatology. J Am Acad Dermatol 2022; 87:e73-e75. [PMID: 33137439 DOI: 10.1016/j.jaad.2020.10.077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 10/05/2020] [Accepted: 10/22/2020] [Indexed: 10/23/2022]
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dos Anjos C, Leanse LG, Liu X, Miranda HV, Anderson RR, Dai T. Antimicrobial Blue Light for Prevention and Treatment of Highly Invasive Vibrio vulnificus Burn Infection in Mice. Front Microbiol 2022; 13:932466. [PMID: 35903474 PMCID: PMC9315199 DOI: 10.3389/fmicb.2022.932466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 06/09/2022] [Indexed: 11/28/2022] Open
Abstract
Vibrio vulnificus is an invasive marine bacterium that causes a variety of serious infectious diseases. With the increasing multidrug-resistant variants, treatment of V. vulnificus infections is becoming more difficult. In this study, we explored antimicrobial blue light (aBL; 405 nm wavelength) for the treatment of V. vulnificus infections. We first assessed the efficacy of aBL against five strains of V. vulnificus in vitro. Next, we identified and quantified intracellular porphyrins in V. vulnificus to provide mechanistic insights. Additionally, we measured intracellular reactive oxygen species (ROS) production and bacterial membrane permeabilization following aBL exposures. Lastly, we conducted a preclinical study to investigate the efficacy and safety of aBL for the prevention and treatment of burn infections caused by V. vulnificus in mice. We found that aBL effectively killed V. vulnificus in vitro in both planktonic and biofilm states, with up to a 5.17- and 4.57-log10 CFU reduction being achieved, respectively, following an aBL exposure of 216 J/cm2. Protoporphyrin IX and coproporphyrins were predominant in all the strains. Additionally, intracellular ROS was significantly increased following aBL exposures (P < 0.01), and there was evidence of aBL-induced permeabilization of the bacterial membrane (P < 0.0001). In the preclinical studies, we found that female mice treated with aBL 30 min after bacterial inoculation showed a survival rate of 81% following 7 days of observation, while only 28% survival was observed in untreated female mice (P < 0.001). At 6 h post-inoculation, an 86% survival was achieved in aBL-treated female mice (P = 0.0002). For male mice, 86 and 63% survival rates were achieved when aBL treatment was given 30 min and 6 h after bacterial inoculation, respectively, compared to 32% survival in the untreated mice (P = 0.0004 and P = 0.04). aBL did not reduce cellular proliferation or induce apoptosis. We found five cytokines were significantly upregulated in the males after aBL treatment, including MCSF (P < 0.001), MCP-5 (P < 0.01), TNF RII (P < 0.01), CXCL1 (P < 0.01), and TIMP-1 (P < 0.05), and one in the females (TIMP-1; P < 0.05), suggesting that aBL may induce certain inflammatory processes. In conclusion, aBL may potentially be applied to prevent and treat V. vulnificus infections.
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Tran TA, Kappelhoff J, Jüstel T, Anderson RR, Purschke M. UV emitting nanoparticles enhance the effect of ionizing radiation in 3D lung cancer spheroids. Int J Radiat Biol 2022; 98:1484-1494. [PMID: 35020574 DOI: 10.1080/09553002.2022.2027541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
PURPOSE Radiation therapy for cancer is limited by damage to surrounding normal tissues, and failure to completely eradicate a tumor. This study investigated a novel radiosensitizer, composed of lutetium phosphate nanoparticles doped with 1% praseodymium and 1.5% neodymium cations (LuPO4:Pr3+,Nd3+). During X-ray exposure, the particles emit UVC photons (200-280 nm), resulting in increased tumor cell death, by oxygen-independent UVC-induced damage. METHODS AND MATERIALS Specially designed LuPO4:Pr3+,Nd3+ nanoscintillator particles were characterized by dynamic light scattering, TEM and emission spectroscopy upon excitation. Cell death was determined by reduction in tumor spheroid growth over a 3-week period using a 3D A549 lung cancer model. Cell cycle was evaluated by flow cytometry and cell death pathways were assessed by Annexin V/PI stain as well as quantify apoptotic bodies. RESULTS Lung cancer cells expressed no long-term or non-specific toxicity when incubated with LuPO4:Pr3+,Nd3+ nanoscintillators. In contrast, there was significant growth inhibition of cell spheres treated with 2.5 mg/ml LuPO4:Pr3+,Nd3+ in combination with ionizing radiation (4 or 8 Gy X-ray), compared to radiation alone. A homogeneous distribution of small NPs throughout the entire sphere resulted in more pronounced lethality and growth inhibition, compared to particle distribution limited to the outer cell layers. Growth inhibition after the combined treatment was caused by necrosis, apoptosis and G2/M cell cycle arrest. CONCLUSIONS Newly designed UVC-emitting nanoscintillators (LuPO4:Pr3+,Nd3+) in combination with ionizing radiation cause tumor sphere growth inhibition by inducing cell cycle arrest, apoptosis and necrosis. UVC-emitting nanoparticles offer a promising new strategy for enhancing local tumor response to ionizing radiation treatment.
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Ross EV, Raythen J, Anderson RR. "Photon recycling" can enhance cutaneous response to lasers: A pilot human study. Lasers Surg Med 2021; 54:152-156. [PMID: 34939685 DOI: 10.1002/lsm.23505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 11/21/2021] [Accepted: 11/25/2021] [Indexed: 11/06/2022]
Abstract
BACKGROUND Depending on wavelength and pigmentation, human skin can reflect up to 70% of incident laser light. AIMS We tested the hypothesis that returning ("recycling") this diffusely reflected light to the site of laser exposure would increase cutaneous response. MATERIALS AND METHODS Thirteen adult volunteers with Fitzpatrick skin types I-IV participated in this IRB-approved study. Matched contralateral test sites on the volar forearms were exposed to a pulsed dye laser operated at 585 nm, 450 microseconds pulse duration in a uniform 5 mm circular exposure spot without skin cooling. On one arm, the laser handpiece was fitted with an aluminized hemispherical mirror with a reflectance of 67%. The minimum fluence causing skin purpura, and the purpura lesion diameter were measured. RESULTS The mean purpura threshold fluence with the reflector was 3.1 J/cm2 (0.5 SD), and 3.7 J/cm2 without the reflector (0.36 SD) (p < 0.001). The mean laser-induced purpura lesion diameter was approximately 5.3 mm with the reflector and 5.0 mm without the reflector. CONCLUSION Consistent with a theoretical model and in vitro measurements, this human study confirms that "recycling" reflected laser light can increase skin response. Potentially, the therapeutic response can also be improved with "photon recycling."
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