Strategies to Improve the Antimicrobial Efficacy of Photodynamic, Sonodynamic, and Sonophotodynamic Therapies

The synergistic effect of photodynamic and sonodynamic inactivation against Candida albicans biofilm

Candida albicans biofilm can cause diseases that are resistant to conventional antifungal agents. Photodynamic (PDI), sonodynamic (SDI), and sonophotodynamic (SPDI) inactivation have arisen as promising antimicrobial strategies. This study evaluated these treatments mediated by curcumin against C. albicans biofilms. For this, C. albicans biofilms were submitted to PDI, SDI, or SPDI with different light and ultrasound doses, then, the viability assay was performed to measure the effectiveness. Finally, a mathematical model was suggested to fit acquired experimental data and understand the synergistic effect of light and ultrasound in different conditions. The results showed that SPDI, PDI, and SDI reduced the viability in 6 ± 1; 1 ± 1; and 2 ± 1 log, respectively, using light at 60 J/cm2, ultrasound at 3 W/cm2, and 80 μM of curcumin. The viability reduction was proportional to the ultrasound and light doses delivered. These results encourage the use of SPDI for the control of microbial biofilm.

Morphological aspects and the effectiveness of photodynamic inactivation against Rhizopus oryzae in different life cycles

Mucormycosis is an extremely aggressive fungal disease with a high mortality rate, especially in people with compromised immune systems. Most cases of mucormycosis are caused by the fungus Rhizopus oryzae. The treatments used are based on high doses of antifungals, associated with surgical resections, when it is possible. However, even with this aggressive treatment, the estimated attributable mortality rate is high. There is therefore a need to develop adjuvant treatments. Photodynamic Inactivation (PDI) may be an auxiliary therapeutic option for mucormycosis. Due to the lack of reports in the literature on the morphology and photodynamic inactivation of R. oryzae, characterization of the fungus using Confocal Microscopy and Transmission Electron Microscopy, and different protocols using Photodithazine® (PDZ), a chlorin e6 compound, as a photosensitizer, were performed. The fungus growth rate under different concentrations and incubation times of the photosensitizer and its association with the surfactant Sodium Dodecyl Sulphate (SDS) was evaluated. For the hyphae, both in the light and dark phases, in the protocols using only PDZ, no effective photodynamic response was observed. Meanwhile with the combination of SDS 0.05% and PDZ, inhibition growth rates of 98% and 72% were achieved for the white and black phase, respectively. In the conidia phase, only a 1.7 log10 reduction of the infective spores was observed. High concentration of melanin and the complex and resistant structures, especially at the black phase, results in a high limitation of the PDI inactivation response. The combined use of the SDS resulted in an improved response, when compared to the one obtained with the amphotericin B treatment.

The Evolution of Sonochemistry: From the Beginnings to Novel Applications

Sonochemistry is the use of ultrasonic waves in an aqueous medium, to generate acoustic cavitation. In this context, sonochemistry emerged as a focal point over the past few decades, starting as a manageable process such as a cleaning technique. Now, it is found in a wide range of applications across various chemical, physical, and biological processes, creating opportunities for analysis between these processes. Sonochemistry is a powerful and eco-friendly technique often called "green chemistry" for less energy use, toxic reagents, and residues generation. It is increasing the number of applications achieved through the ultrasonic irradiation (USI) method. Sonochemistry has been established as a sustainable and cost-effective alternative compared to traditional industrial methods. It promotes scientific and social well-being, offering non-destructive advantages, including rapid processes, improved process efficiency, enhanced product quality, and, in some cases, the retention of key product characteristics. This versatile technology has significantly contributed to the food industry, materials technology, environmental remediation, and biological research. This review is created with enthusiasm and focus on shedding light on the manifold applications of sonochemistry. It delves into this technique's evolution and current applications in cleaning, environmental remediation, microfluidic, biological, and medical fields. The purpose is to show the physicochemical effects and characteristics of acoustic cavitation in different processes across various fields and to demonstrate the extending application reach of sonochemistry. Also to provide insights into the prospects of this versatile technique and demonstrating that sonochemistry is an adapting system able to generate more efficient products or processes.

Application of antimicrobial sonodynamic therapy as a potential treatment modality in dentistry: A literature review

The accumulation of dental plaque is a precursor to various dental infections, including lesions, inflammation around dental implants, and inflammation under dentures. Traditional cleaning methods involving physical removal and chemical agents often fall short of eliminating bacteria and their protective biofilms. These methods can also inadvertently lead to bacteria that resist drugs and upset the mouth's microbial harmony. To counter these issues, a new approach is needed that can target and clear away dental plaque, minimize biofilms and bacteria, and thus support sustained dental health. Enter antimicrobial sonodynamic therapy (aSDT), a supplementary treatment that uses gentle ultrasound waves to trigger a sonosensitizer compound, destroying bacterial cells. This process works by generating heat, mechanical pressure, initiating chemical reactions, and producing reactive oxygen species (ROS), offering a fresh tactic for managing dental plaque and biofilms. The study reviews how aSDT could serve as an innovative dental treatment option to enhance oral health.

An update on alternative therapy for Escherichia coli causing urinary tract infections; a narrative review

BACKGROUND

Urinary tract infections (UTIs) are the most common type of nosocomial infection and severe health issues because of the difficulties and frequent recurrence. Today, alternative methods such as sonodynamic therapy (SDT), photodynamic therapy (PDT) and herbal materials use for treating infections like UTI in many countries.

METHOD

We conducted searches of the biomedical databases (Google Scholar, Scopus, PubMed, and Web of sciences) to identify related studies from 2008 to 2023.

RESULT

SDT aims to use ultrasound to activate a sonosensitizer, which causes a biological effect by raising reactive oxygen species (ROS). When bacteria are exposed to ROS, several important effects occur: oxidative damage, DNA damage, protein dysfunction etc. SDT with herbal medicine significantly reduced the number of colony-forming units and bactericidal activity for Klebsiella pneumonia and E. coli. PDT is a promising treatment for cancer and microbial infections, combining a photosensitiser, light and tissue molecular oxygen. It involves a photosensitizer, light source, and oxygen, with variations affecting microbial binding and bactericidal activity. Factors affecting antibacterial properties include plant type, growing conditions, harvesting, and processing. This review highlights the recent advancements in sonodynamic, photodynamic, herbal, and bio-material-based approaches in the treatment of E. coli infections.

CONCLUSIONS

These alternative therapies offer exciting prospects for addressing UTIs, especially in cases where traditional antibiotic treatments may be less effective. Further research and clinical studies are warranted to fully explore the potential of these innovative treatment modalities in combating UTIs and improving patient outcomes.

Effects on Colonization Factors and Mechanisms Involved in Antimicrobial Sonophotodynamic Inactivation Mediated by Curcumin

Photodynamic (PDI) and sonodynamic (SDI) inactivation have been successfully employed as antimicrobial treatments. Moreover, sonophotodynamic inactivation (SPDI), which is the simultaneous application of PDI and SDI, has demonstrated greater effects. This study assessed the effects of PDI (PDI group), SDI (SDI group) and SPDI (SPDI group) using curcumin as a sensitizer on the metabolism, adhesion capability, biofilm formation ability and structural effects in a Staphylococcus aureus biofilm. Moreover, the production of reactive oxygen species (ROS) and the degradation spectrum of curcumin under the irradiation sources were measured. SPDI was more effective in inactivating the biofilm than PDI and SDI. All treatments reduced the adhesion ability of the bacteria: 58 ± 2%, 58 ± 1% and 71 ± 1% of the bacterial cells adhered to the polystyrene plate after the SPDI, SDI and PDI, respectively, when compared to 79 ± 1% of the untreated cells (control group). This result is probably related to the metabolism cell reduction after treatments. The metabolism of cells from the PDI group was 89 ± 1% lower than the untreated cells, while the metabolic activity of SDI and SPDI groups were 82 ± 2% and 90 ± 1% lower, respectively. Regarding the biofilm formation ability, all treatments (SPDI, SDI and PDI) reduced the total biomass. The total biomass of the PDI, SDI and SPDI groups were 26 ± 2%, 31 ± 5% and 35 ± 6% lower than the untreated biofilm (control group), respectively. Additionally, all treatments produced ROS and caused significant structural changes, reducing cells and the extracellular matrix. The light caused a greater absorbance decay of the curcumin; however, the US did not expressively alter its spectrum. Finally, SPDI had improved antimicrobial effects, and all treatments exhibited similar effects in the colonization factors evaluated.

Antimicrobial photodynamic therapy against oral biofilm: influencing factors, mechanisms, and combined actions with other strategies

Oral biofilms are a prominent cause of a wide variety of oral infectious diseases which are still considered as growing public health problems worldwide. Oral biofilms harbor specific virulence factors that would aggravate the infectious process and present resistance to some traditional therapies. Antimicrobial photodynamic therapy (aPDT) has been proposed as a potential approach to eliminate oral biofilms via in situ-generated reactive oxygen species. Although numerous types of research have investigated the effectiveness of aPDT, few review articles have listed the antimicrobial mechanisms of aPDT on oral biofilms and new methods to improve the efficiency of aPDT. The review aims to summarize the virulence factors of oral biofilms, the progress of aPDT in various oral biofilm elimination, the mechanism mediated by aPDT, and combinatorial approaches of aPDT with other traditional agents.

Sonophotodynamic inactivation of Pseudomonas aeruginosa biofilm mediated by curcumin

The inactivation of Pseudomonas aeruginosa biofilm is a major challenge, as biofilms are less responsive to conventional treatments and responsible for persistent infections. This has led to the investigation of alternative approaches for biofilm control such as photodynamic (PDI) and sonodynamic (SDI) inactivation. The combination of them, known as Sonophotodynamic Inactivation (SPDI), has improved the effectiveness of the process. Curcumin, a well-established photosensitizer, has been identified as a potential sonosensitizer. This study evaluated the most effective combination for SPDI against P. aeruginosa biofilms in vitro, varying curcumin concentrations and ultrasound intensities. The results indicated that the inactivation was directly proportional to the curcumin concentration. Using curcumin 120 µM and 3.0 W.cm-2 of ultrasound intensity, SPDI demonstrated the highest and the best synergistic results, equivalent to 6.9 ± 2.1 logs of reduction. PDI reduced 0.7 ± 0.9 log and SDI had no effect. In conclusion, SPDI with curcumin is a promising approach for biofilm inactivation.

PLGA nanoparticles loaded with curcumin produced luminescence for cell bioimaging

To revise the emission of curcumin (Cur) from "off" to "on", poly (D, L-lactide-co-glycolide) acid (PLGA) nanoparticles loaded with Cur were embedded in a polyvinyl alcohol (PVA) emulsifier (named Cur@PLGA-NPs). First, the emission intensities of different nanoformulations, including liposomes, bovine serum albumin (BSA) nanoparticles, and PLGA nanoparticles, were examined to discover the most effective carriers for Cur luminescence. As a result, Cur@PLGA-NPs exhibited the highest fluorescence intensity due to aggregation-induced emission (AIE), with quantum yields of 23.78% in aqueous solution and 21.52% in the solid state. According to X-ray diffraction (XRD) data, Cur@PLGA-NPs existed in the amorphous state, with a size of 217.2 ± 5.2 nm, an encapsulation efficiency (EE) of 69.98%, and a drug loading efficiency (LE) of 1.37%. The intramolecular interactions, which included hydrophobic interactions, electrostatic interactions, π-π interactions and solvatochromic effects, stabilized the chromophore cluster of Cur@PLGA-NPs in terms of nanoparticle formulation. Compared with free Cur, Cur@PLGA-NPs sensitized CT26 cells more efficiently with an IC₅₀ value of 16.9 μmol/L and an apoptotic rate of 17.20% at 10 μmol/L Cur. Because of the robust fluorescence emission based on AIE, Cur@PLGA-NPs were utilized as a nano-AIE probe for cell bioimaging, and many red fluorescent signals were observed in CT26 cells after treatment. These results suggest that Cur@PLGA-NPs provide a novel amorphous AIE formulation with imaging and bioactive capabilities.

Titanium-Based Nanoarchitectures for Sonodynamic Therapy-Involved Multimodal Treatments

Sonodynamic therapy (SDT) has considerably revolutionized the healthcare sector as a viable noninvasive therapeutic procedure. It employs a combination of low-intensity ultrasound and chemical entities, known as a sonosensitizer, to produce cytotoxic reactive oxygen species (ROS) for cancer and antimicrobial therapies. With nanotechnology, several unique nanoplatforms are introduced as a sonosensitizers, including, titanium-based nanomaterials, thanks to their high biocompatibility, catalytic efficiency, and customizable physicochemical features. Additionally, developing titanium-based sonosensitizers facilitates the integration of SDT with other treatment modalities (for example, chemotherapy, chemodynamic therapy, photodynamic therapy, photothermal therapy, and immunotherapy), hence increasing overall therapeutic results. This review summarizes the most recent developments in cancer therapy and tissue engineering using titanium nanoplatforms mediated SDT. The synthesis strategies and biosafety aspects of Titanium-based nanoplatforms for SDT are also discussed. Finally, various challenges and prospects for its further development and potential clinical translation are highlighted.

Photodynamic therapy: Innovative approaches for antibacterial and anticancer treatments

Photodynamic therapy is an alternative treatment mainly for cancer but also for bacterial infections. This treatment dates back to 1900 when a German medical school graduate Oscar Raab found a photodynamic effect while doing research for his doctoral dissertation with Professor Hermann von Tappeiner. Unexpectedly, Raab revealed that the toxicity of acridine on paramecium depends on the intensity of light in his laboratory. Photodynamic therapy is therefore based on the administration of a photosensitizer with subsequent light irradiation within the absorption maxima of this substance followed by reactive oxygen species formation and finally cell death. Although this treatment is not a novelty, there is an endeavor for various modifications to the therapy. For example, selectivity and efficiency of the photosensitizer, as well as irradiation with various types of light sources are still being modified to improve final results of the photodynamic therapy. The main aim of this review is to summarize anticancer and antibacterial modifications, namely various compounds, approaches, and techniques, to enhance the effectiveness of photodynamic therapy.

Enhancement of hypericin nanoparticle-mediated sonoinduced disruption of biofilm and persister cells of Streptococcus mutans by dermcidin-derived peptide DCD-1L

BACKGROUND

Streptococcus mutans is considered a major significant contributor to dental caries and its effective removal is difficult due to the formation of biofilm. Therefore, the development of adjuvant therapeutic strategies with anti-biofilm properties is a promising approach. In the present study, we examined the effect of dermcidin-derived peptide DCD-1 L on the antibacterial activity of hypericin nanoparticle (HypNP)-mediated antimicrobial sonodynamic therapy (aSDT) against persister cells growing- and biofilm cultures of S. mutans.

MATERIALS AND METHODS

Following synthesis and confirmation of HypNP, the fractional inhibitory concentration (FIC) index of HypNP and DCD-1 L was determined by checkerboard assay. Cellular uptake of HypNP-DCD-1 L and generation of endogenous reactive oxygen species (ROS) were assessed and followed by the determination of antimicrobial sonoactivity of HypNP-DCD-1 L against persister cells growing- and biofilm cultures of S. mutans. The water-insoluble extracellular polysaccharide (EPS) and expression of the gtfD, comDE, and smuT genes were then evaluated in persister cells growing- and biofilm cultures of S. mutans.

RESULTS

There was a synergistic activity in the combination of HypNP and DCD-1 L against S. mutans with an FIC index value of 0.37. The HypNP-DCD-1L-mediated aSDT also displayed the highest cellular uptake and endogenous ROS generation by bacterial cells. When biofilm and persister cells of S. mutans were treated with HypNP-DCD-1 L and subsequently exposed to ultrasound waves, 5.1 log and 3.8 log reductions, respectively, in bacterial numbers were observed (P<0.05). According to the data, EPS in both persister cells growing- and biofilm cultures of S. mutans were significantly decreased after exposure to the HypNP-DCD-1L-mediated aSDT (P<0.05). In addition, the quantitative real-time PCR data illustrated the high level of similarities in very low-expression profiles of the gtfD before and after all treated groups for persister cells. While, following HypNP-DCD-1L-mediated aSDT treatment, the expression levels of gtfD, comDE, and smuT were significantly lower in treated persister cells growing- and biofilm cultures of S. mutans in comparison with control groups (P<0.05).

CONCLUSIONS

Combined, the results of this study indicate that ultrasound waves-activated HypNP-DCD-1 L can sonoinactivate S. mutans biofilms and persister cells, as well as reduce effectively pathogenicity potency of S. mutans. Hence, HypNP-DCD-1L-mediated aSDT may be proposed as a promising adjunctive therapeutic approach for dental caries.

Antimicrobial activity of D-amino acid in combination with photo-sonoactivated hypericin nanoparticles against Acinetobacter baumannii

BACKGROUND

The emergence of multidrug-resistant Acinetobacter baumannii strains is increasing worldwide. To overcome these life-threatening infections, the development of new treatment approaches is critical. For this purpose, this study was conducted to determine the antimicrobial photo-sonodynamic therapy (aPSDT) using hypericin nanoparticles (HypNP) in combination with D-Tryptophan (D-Trp) against A. baumannii.

MATERIALS AND METHODS

HypNP was synthesized and characterized, followed by the determination of the fractional inhibitory concentration (FIC) index of HypNP and D-Trp by checkerboard assay. Next, the antimicrobial and anti-biofilm potential of HypNP@D-Trp-mediated aPSDT against A. baumannii was evaluated. Finally, the anti-virulence activity of aPSDT using HypNP@D-Trp was accessed following the characterization of HypNP@D-Trp interaction with AbaI using in silico virtual screening and molecular docking.

RESULTS

A synergistic activity in the combination of HypNP and D-Trp against A. baumannii was observed with a FIC index value of 0.5. There was a 5.10 log₁₀ CFU/mL reduction in the cell viability of A. baumannii when the bacterial cells were treated with 1/2 × MIC of HypNP@D-Trp and subsequently exposed to ultrasound waves and blue light (P < 0.05). Moreover, a significant biofilm degradation effect on biofilm-associated cells of A. baumannii was observed after treatment with aPSDT using 2 × MIC of HypNP@D-Trp in comparison with the control groups (P < 0.05). According to the molecular docking analysis of the protein-ligand complex, Hyp with a high affinity for AbaI showed a binding affinity of - 9.41 kcal/mol. Also, the expression level of abaI gene was significantly downregulated by 10.32-fold in A. baumannii treated with aPSDT as comprised with the control group (P < 0.05).

CONCLUSIONS

It can be concluded that HypNP@D-Trp-mediated aPSDT can be considered a promising strategy to overcome the infections caused by A. baumannii by reducing the growth of bacterial biofilm and decreasing the expression of abaI as a gene involved in A. baumannii biofilm formation.

Photodisinfection of material surfaces and bacterial skin infections by a detergent loaded with curcumin

The development of technologies and therapeutic strategies is needed to combat skin infections and pathogenic microorganisms present on material surfaces that are still responsible for serious public health problems. In this study, detergents loaded with curcumin were prepared by a simple approach and characterized by UV-vis spectroscopy and fluorescence spectroscopy. Their antibacterial photodynamic effects were evaluated against Staphylococcus aureus in planktonic medium and in vivo (skin infection model), and showed a reduction up to 8 logs and 2 logs, respectively. Additionally, the curcumin-detergents were applied on photodisinfection of material surfaces such as wood, rubber, and stainless steel resulting in an efficient photoinactivation up to 3 logs. These developed detergents loaded with curcumin can improve the decontamination of material surfaces and skin infections (in vivo) when illuminated.

Excited state and reactive oxygen species against cancer and pathogens: a review on sonodynamic and sono-photodynamic therapy

Photodynamic and sonodynamic therapy are therapies having great potential in the treatment of bacterial infections and cancer. Their background is associated with photo- and sonosensitizers - substances that can be excited when exposed to light or ultrasound. These sensitizers belong to a variety of compounds groups, including porphyrins, porphyrazines, and phthalocyanines. Releasing the energy when returning to the ground state can occur in the manner of transferring it to oxygen molecules, leading to reactive oxygen species able to disrupt membranes of bacterial and cancer cells, leaving the organism's cells unaffected. In recent years, the number of reports on numerous sensitizers being effective has been constantly growing. Therefore, the development of this field may prove beneficial for dealing with cancer and microbes. This review describes the development of photodynamic and sonodynamic therapy, as well as their combination, with emphasize on sonodynamic therapy and its potential in the treatment of cancer and bacterial infections.

Enhanced antimicrobial activity through the combination of antimicrobial photodynamic therapy and low-frequency ultrasonic irradiation

The rapid increase of antibiotic resistance in pathogenic microorganisms has become one of the most severe threats to human health. Antimicrobial photodynamic therapy (aPDT), a light-based regimen, has offered a compelling nonpharmacological alternative to conventional antibiotics. The activity of aPDT is based on cytotoxic effect of reactive oxygen species (ROS), which are generated through the photosensitized reaction between photon, oxygen and photosensitizer. However, limited by the penetration of light and photosensitizers in human tissues and/or the infiltration of oxygen and photosensitizers in biofilms, the eradication of deeply located or biofilm-associated infections by aPDT remains challenging. Ultrasound irradiation bears a deeper penetration in human tissues than light and, sequentially, can promote drug delivery through cavitation effect. As such, the combination of ultrasound and aPDT represents a potent antimicrobial strategy. In this review, we summarized the recent progresses in the area of the combination therapy using ultrasound and aPDT, and discussed the potential mechanisms underlying enhanced antimicrobial effect by this combination therapy. The future research directions are also highlighted.

Curcumin-Mediated Sono-Photodynamic Treatment Inactivates Listeria monocytogenes via ROS-Induced Physical Disruption and Oxidative Damage

Sono-photodynamic sterilization technology (SPDT) has become a promising non-thermal food sterilization technique because of its high penetrating power and outstanding microbicidal effects. In this study, Listeria monocytogenes (LMO) was effectively inactivated using curcumin as the sono-photosensitizer activated by ultrasound and blue LED light. The SPDT treatment at optimized conditions yielded a 4-log reduction in LMO CFU. The reactive oxygen species (ROS) production in LMO upon SPDT treatment was subsequently investigated. The results demonstrated SPDT treatment-induced excessive ROS generation led to bacterial cell deformation and membrane rupture, as revealed by the scanning electron microscope (SEM) and cytoplasmic material leakage. Moreover, agarose gel electrophoresis and SDS-PAGE further revealed that SPDT also triggered bacterial genomic DNA cleavage and protein degradation in LMO, thus inducing bacterial apoptosis-like events, such as membrane depolarization.

Contribution of antimicrobial photo-sonodynamic therapy in wound healing: an in vivo effect of curcumin-nisin-based poly (L-lactic acid) nanoparticle on Acinetobacter baumannii biofilms

BACKGROUND

The biofilm-forming ability of Acinetobacter baumannii in the burn wound is clinically problematic due to the development of antibiotic-resistant characteristics, leading to new approaches for treatment being needed. In this study, antimicrobial photo-sonodynamic therapy (aPSDT) was used to assess the anti-biofilm efficacy and wound healing activity in mice with established A. baumannii infections.

METHODS

Following synthesis and confirmation of Curcumin-Nisin-based poly (L-lactic acid) nanoparticle (CurNisNp), its cytotoxic and release times were evaluated. After determination of the sub-significant reduction (SSR) doses of CurNisNp, irradiation time of light, and ultrasound intensity against A. baumannii, anti-biofilm activity and the intracellular reactive oxygen species (ROS) generation were evaluated. The antibacterial and anti-virulence effects, as well as, histopathological examination of the burn wound sites of treated mice by CurNisNp-mediated aPSDTSSR were assessed and compared with silver sulfadiazine (SSD) as the standard treatment group.

RESULTS

The results showed that non-cytotoxic CurNisNp has a homogeneous surface and a sphere-shaped vesicle with continuous release until the 14th day. The dose-dependent reduction in cell viability of A. baumannii was achieved by increasing the concentrations of CurNisNp, irradiation time of light, and ultrasound intensity. There was a time-dependent reduction in biofilm growth, changes in gene expression, and promotion in wound healing by the acceleration of skin re-epithelialization in mice. Not only there was no significant difference between aPSDTSSR and SSD groups in antibacterial and anti-virulence activities, but also wound healing and re-epithelialization occurred more efficiently in aPSDTSSR than in the SSD group.

CONCLUSIONS

In conclusion, CurNisNp-mediated aPSDT might be a promising complementary approach to treat burn wound infections.

Antimicrobial Photodynamic Therapy: Latest Developments with a Focus on Combinatory Strategies

Antimicrobial photodynamic therapy (aPDT) has become a fundamental tool in modern therapeutics, notably due to the expanding versatility of photosensitizers (PSs) and the numerous possibilities to combine aPDT with other antimicrobial treatments to combat localized infections. After revisiting the basic principles of aPDT, this review first highlights the current state of the art of curative or preventive aPDT applications with relevant clinical trials. In addition, the most recent developments in photochemistry and photophysics as well as advanced carrier systems in the context of aPDT are provided, with a focus on the latest generations of efficient and versatile PSs and the progress towards hybrid-multicomponent systems. In particular, deeper insight into combinatory aPDT approaches is afforded, involving non-radiative or other light-based modalities. Selected aPDT perspectives are outlined, pointing out new strategies to target and treat microorganisms. Finally, the review works out the evolution of the conceptually simple PDT methodology towards a much more sophisticated, integrated, and innovative technology as an important element of potent antimicrobial strategies.

Antibacterial Sonodynamic Therapy: Current Status and Future Perspectives

Multidrug-resistant bacteria have emerged in both community and hospital settings, partly due to the misuse of antibiotics. The inventory of viable antibiotics is rapidly declining, and efforts toward discovering newer antibiotics are not yielding the desired outcomes. Therefore, alternate antibacterial therapies based on physical mechanisms such as light and ultrasound are being explored. Sonodynamic therapy (SDT) is an emerging therapeutic approach that involves exposing target tissues to a nontoxic sensitizing chemical and low-intensity ultrasound. SDT can enable site-specific cytotoxicity by producing reactive oxygen species (ROS) in response to ultrasound, which can be harnessed for treating bacterial infections. This approach can potentially be used for both superficial and deep-seated microbial infections. The majority of the sonosensitizers reported are nonpolar, exhibiting limited bioavailability and a high clearance rate in the body. Therefore, targeted delivery agents such as nanoparticle composites, liposomes, and microbubbles are being investigated. This article reviews recent developments in antibacterial sonodynamic therapy, emphasizing biophysical and chemical mechanisms, novel delivery agents, ultrasound exposure and image guidance strategies, and the challenges in the pathway to clinical translation.

Antimicrobial Activity of Curcumin in Nanoformulations: A Comprehensive Review

Curcumin (CUR) is a natural substance extracted from turmeric that has antimicrobial properties. Due to its ability to absorb light in the blue spectrum, CUR is also used as a photosensitizer (PS) in antimicrobial Photodynamic Therapy (aPDT). However, CUR is hydrophobic, unstable in solutions, and has low bioavailability, which hinders its clinical use. To circumvent these drawbacks, drug delivery systems (DDSs) have been used. In this review, we summarize the DDSs used to carry CUR and their antimicrobial effect against viruses, bacteria, and fungi, including drug-resistant strains and emergent pathogens such as SARS-CoV-2. The reviewed DDSs include colloidal (micelles, liposomes, nanoemulsions, cyclodextrins, chitosan, and other polymeric nanoparticles), metallic, and mesoporous particles, as well as graphene, quantum dots, and hybrid nanosystems such as films and hydrogels. Free (non-encapsulated) CUR and CUR loaded in DDSs have a broad-spectrum antimicrobial action when used alone or as a PS in aPDT. They also show low cytotoxicity, in vivo biocompatibility, and improved wound healing. Although there are several in vitro and some in vivo investigations describing the nanotechnological aspects and the potential antimicrobial application of CUR-loaded DDSs, clinical trials are not reported and further studies should translate this evidence to the clinical scenarios of infections.