With the increasing number of pathogenic microbes that are becoming resistant to routinely used antimicrobials, it is important to look to non-traditional approaches for the treatment of infections. Antimicrobial blue light (aBL;405 nm) is a novel strategy for the treatment of infections. Here we report an investigation into the potential for resistance development to aBL in three clinically important Gram-negative bacteria, through sequential exposure in vitro and in vivo. We found that 20 cycles of aBL exposure, in vitro, did not incur resistance development, in any of the species tested (Acinetobacter baumanii, Pseudomonas aeruginosaor Escherichia coli). In addition, sub-curative sequential aBL treatment of a wound infected with a bioluminescent variant of the P. aeruginosa PAO1 strain, did not influence sensitivity to aBL. In conclusion, it is unlikely that sequential treatment of aBL will result in resistance generation, suggesting that multiple treatments of aBL may be administered without resistance development becoming a concern.
Antibiotic resistance is one of the most serious threats to public health. It is estimated that at least 23,000 people die each year in the USA as a direct result of antibiotic-resistant infections. In addition, many antibiotic-resistant microorganisms develop biofilms, surface-associated microbial communities that are extremely resistant to antibiotics and the immune system. A light-based approach, antimicrobial blue light (aBL), has attracted increasing attention due to its intrinsic antimicrobial effect without the involvement of exogenous photosensitizers. In this study, we investigated the effectiveness of this non-antibiotic approach against biofilms formed by multidrug-resistant (MDR) microorganisms. MDR Acinetobacter baumannii, Escherichia coli, Candida albicans, and Pseudomonas aeruginosa biofilms were grown either in 96-well microtiter plates for 24 h or in a CDC biofilm reactor for 48 h, and then exposed to aBL at 405 nm emitted from a light-emitting diode (LED). We demonstrated that, for the biofilms grown in the CDC biofilm reactor, approximately 1.88 log10 CFU reduction was achieved in A. baumannii, 2.78 log10 CFU in E. coli and 3.18 log10 CFU in P. aeruginosa after 162 J/cm2 , 576 J/cm2 and 500 J/cm2 aBL were delivered, respectively. For the biofilms formed in the 96-well microtiter plates, 5.67 and 2.46 log10 CFU reduction was observed in P. aeruginosa and C. albicans polymicrobial biofilm after an exposure of 216 J/cm2 . In conclusion, aBL is potentially an alternative non-antibiotic approach against MDR biofilm-related infections. Future studies are warranted to investigate other important MDR microorganisms, the mechanism of action of aBL, and aBL efficacy in vivo.
Background: An increasing prevalence of Candida infections has emerged with the wide use of immune-suppressants and antibiotics. Photodynamic inactivation (PDI) as a new approach to treat localized Candida infections is an emerging and promising field nowadays. This study evaluated the efficacy of photodynamic therapy using two new Cationic benzylidene cyclopentanone photosensitizers(P1 and P2) against strains of clinical fluconazole–resistant Candida albicans.
Methods: Suspensions and biofilms of Candida species were incubated with P1 and P2 concentrations (0.25~50 μM) for 30 min followed by 532nm laser irradiation. For planktonic suspensions, viability of cells was assayed by CFU counting. For biofilms, the metabolic activity was evaluated by XTT. Results: In PDI of a planktonic culture of clinical fluconazole–resistant Candida albicans, P2 showed the higher efficacy. After incubation with 25 μM of P2 for 30 min and irradiation with 532nm laser (36 J cm-2), the viability of C. albicans planktonic cells decreased by 3.84 log10. For biofilm cells, a higher light dose of 75 mW cm-2 was necessary to achieve 97.71% metabolic activity reduction.
Conclusions: The results of this investigation demonstrated that benzylidene cyclopentanone photosensitizer(P2)is an efficient photosensitizer to kill C. albicans. Moreover, single-species biofilms were less susceptible to PDT than their planktonic counterparts.
The 3D fabrication of bio-compatible materials under an aqueous environment is a fundamental requirement for tissue
engineering. In this work, a series of polyethylene glycol- (PEG-), carboxylate anionic group- or pyridyl cationic groupfunctionalized
benzylidene cyclopentanone photo-initiators (B2, B3, X2, X3, Y1 and P1) were synthesized. Their
water-solubility, photophysical properties and cytotoxicity were investigated. Using eosin as reference, their initiation
efficiencies in water-soluble photoactive formulation (SR610 with 20% of DI water) excited by one- or two-photon were
studied. The results showed that there were no significant differences on partial linear photophysical properties of these
initiators, such as [see manuscript] and [see manuscript], but differences on their (see manuscript), Φ, and σmax are clear. In addition, their cytotoxicity
is different. Two PEG-functionalized initiators (B3 and X3) with two PEG groups on one side of benzylidene
cyclopentanone cores have obvious toxicity, while other four intiators are safety to HepG2 cells at the concentration of
20 μM. Moreover, the water-solubility of X2 and X3 (containing two longer PEG) were much better than those of other
four initiators. Using these initiators, 3D micro-structures fabricated by two-photon polymerization of water-soluble
acrylate all could be achieved. In addition, their threshold energies were all lower than 0.5 mW. However, the stiffness of
3D micro-structures was affected by the water-solubility of these photo-initiators. Those structures built by formulations
containing X2 and X3 would collapse easily. Conversely, other structures could sustain very well. This work proves that
B2,Y1,and P1 have extensive application prospects in 3D fabrication for tissue engineering.
A series of amphiphilic benzylidene cycloalkanes ketone photosensitizers C1-C4 with or without folate receptor-targeted
agent were designed and synthesized. Their photophysical properties and in vitro photodynamic therapy (PDT) effects
were studied. The results showed that all compounds exhibited appropriate lipid-water partition coefficients and high
reactive oxygen yields. The introduction of the folate receptor-targeted agent had no obvious influence on the basic
photophysical & photochemical properties of C2 and C4 compared to those of their corresponding prototype compounds
(C1 and C3). In vitro studies were carried out using MCF-7 cells (FR+), Hela cells (FR+) and A549 cells (FR-), which
represented different levels of folate receptor (FR) expression. All of C1-C4 showed low dark toxicity and superior PDT
effects compared with the clinical drug PSD-007 (a mixture of porphyrins). What’s more, folate receptor-targeted
photosensitizers (C2 and C4) achieved higher accumulation and more excellent PDT effects in MCF-7 cells (FR+) and
Hela cells (FR+) than photosensitizers (C1 and C3) without folate receptor-targeted agent and PSD-007. The photocytotoxicity
of these photosensitizers showed no obvious differences in A549 cells (FR-).
A series of benzylidene cyclopentanone photosensitizers modified by polyethylene glycol, carboxylate anionic or pyridyl
cationic groups with gradient lipid-water partition coefficients were reported. Detailed characterization and systematic
studies of these photosensitizers, including their linear and nonlinear photophysical properties, in vitro photodynamic
therapy (PDT) and two-photon excited PDT (2PE–PDT) activities were conducted and compared with a clinical drug
PSD-007 (a mixture of porphyrins). Three of them exhibited appropriate lipid-water partition coefficients, high reactive
oxygen yields, large two-photon absorption cross-section and low dark toxicity under therapy dosage, could be absorbed
efficiently by liver hepatocellular HepG2 cells and presented strong PDT and 2PE-PDT activity by in vitro cell
experiments. Furthermore, in vivo tumor experiments were carried out on BALB/c mouse models using B3 as the
photosensitizer. The results showed that the tumor growth could be effectively suppressed by B3 under 2PE-PDT. This
work demonstrated the feasibility of using a simple molecular structure to construct high efficient photosensitizers for
2PE-PDT.
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