Targeted, triggered drug delivery to tumor and biofilm microenvironments

Biovalorization of whey waste as economic nutriment for mycogenic production of single cell oils with promising antibiofilm and anticancer potentiality

The production of value-added bio-compounds from rejuvenated sources and their recruitment for healthcare services are paramount objectives in the agenda of white biotechnology. Hereupon, the current study focused on economic production of single cell oils (SCOs) from oleaginous fungi Alternaria sp. (A-OS) and Drechslera sp. (D-OS) using cheese whey waste stream, followed by their evaluation as antibiofilm and anticancer agents, for the first time. As a sole substrate for growth, the whey aided in lipid accumulation by 3.22 and 4.33 g/L, which representing 45.3 and 48.2% lipid content in Drechslera sp. (D-OS) and Alternaria sp. (A-OS), respectively. Meanwhile, a higher unsaturation degree was detected in A-OS by 62.18% comparing to 53.15% of D-OS, with advantageous presence of omega-6 poly unsaturated fatty acid by 22.67% and 15.04% for A-OS and D-OD, respectively, as revealed by GC-MS and FTIR characterization analysis. Interestingly, an eminent and significant (P ≤ 0.05) antibiofilm potency was observed in a dose-dependent modality upon employing both SCOs as antibiofilm agents. Whereas, 100 µg/mL of A-OS recorded superior inhibition of P. aeruginosa, S. aureus and C. albicans biofilms development by 84.10 ± 0.445, 90.37 ± 0.065 and 94.96 ± 0.21%, respectively. Whereas, D-OS (100 µg/mL) thwarted the biofilms of P. aeruginosa, S. aureus and C. albicans by 47.41 ± 2.83, 62.63 ± 5.82 and 78.67 ± 0.23%, correspondingly. Besides, the metabolic performance of cells within biofilm matrix, protein, carbohydrate contents and hydrophobicity of examined biofilms were also curtailed in a significant correlation with biofilm biomass (r ≥ 0.9). Further, as anticancer agents, D-OS recorded higher potency against A549 and CaCo-2 cell lines with IC50 values of 2.55 and 3.425% and SI values of 10.1 and 7.5, respectively. However, A-OS recorded 8.275% and 2.88 for IC50 and SI of Caco-2 cells, respectively. Additionally, A-OS activated caspase 3 by 64.23 ± 1.18% and 53.77 ± 0.995% more than D-OS (52.09 ± 0.222% and 49.72 ± 0.952%) in A549 and Caco-2 cells, respectively. Furthermore, the enzymes, which associated with cancer invasion, metastasis, and angiogenesis (i.e., MMP2 and MMP9) were strongly inhibited by A-OS with 18.58% and 8.295%, respectively as IC50 values; while D-OS results recorded 23.61% and 13.16%, respectively, which could be ascribed to the higher ω-6/ω-3 contents of A-OS. The promising results of the current study opens up the vision to employ SCOs as anti-infective nutraceuticals and in complementary/alternative therapy and prophylactic programs as well.

Activity of Fluoroquinolones and Proton Pump Inhibitors against Resistant Oral Bacterial Biofilms, in silico and in vitro Analysis

Oral bacterial infections are a great health concern worldwide especially in diabetic patients. Emergence of antimicrobial resistance with reference to biofilms in oral cavity is of great concern. We investigated antibiotics combination with proton pump inhibitors against oral clinical isolates. The strains were identified as Staphylococcus epidermidis and Staphylococcus aureus by the 16S rRNA gene sequencing. In molecular docking, ciprofloxacin, levofloxacin, and omeprazole best fit to active pockets of transcriptional regulators 4BXI and 3QP1. None of the proton pump inhibitors were active against S. epidermidis, whereas omeprazole showed significant inhibition (MIC 3.9 μg/ml). Fluoroquinolones were active against both S. epidermidis and S. aureus. In combination analysis, a marked decrease in minimum inhibitory concentration was noticed with omeprazole (MIC 0.12 μg/ml). In antiquorum sensing experiments, a significant inhibitory zone was shown for all fluoroquinolones (14-20 mm), whereas among proton pump inhibitors, only omeprazole (12 ± 0.12 mm) was active against Chromobacterium violaceum. In combination analysis, a moderate increase in antiquorum sensing activity was recorded for ciprofloxacin, ofloxacin, and proton pump inhibitors. Further, significant S. aureus biofilm eradication was recorded using of ciprofloxacin, levofloxacin, and omeprazole combination (78 ± 2.1%). The time-kill kinetic studies indicated a bactericidal effect by ciprofloxacin: levofloxacin: omeprazole combination over 24 hrs. It was concluded that fluoroquinolone combined with omeprazole could be an effective treatment option for eradicating oral bacterial biofilms.

Tailored Phototherapy Agent by Infection Site In Situ Activated Against Methicillin-Resistant S. aureus

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is a promising treatment approach for multidrug resistant infections. PDT/PTT combination therapy can more efficiently eliminate pathogens without drug resistance. The key to improve the efficacy of photochemotherapy is the utilization efficiency of non-radiation energy of phototherapy agents. Herein, a facile phototherapy molecule (SCy-Le) with the enhancement of non-radiative energy transfer is designed by an acid stimulation under a single laser. Introduction of the protonated receptor into SCy-Le results in a distorted intramolecular charge in the infected acidic microenvironment, pH ≈ 5.5, which in turn, enhances light capture, reduces the singlet-triplet transition energies (ΔES1-T1), promotes electron system crossing, enhances capacity of reactive oxygen species generation, and causes a significant increase in temperature by improving vibrational relaxation. SCy-Le shows more than 99% bacterial killing rate against both methicillin-resistant Staphylococcus aureus and its biofilms in vitro and causes bacteria-induced wound healing in mice. This work will provide a new perspective for the design of phototherapy agents, and the emerging photochemotherapy will be a promising approach to combat the problem of antibiotic resistance.

Flexible nanoplatform facilitates antibacterial phototherapy by simultaneously enhancing photosensitizer permeation and relieving hypoxia in bacterial biofilms

Antimicrobial phototherapy has gained recognition as a promising approach for addressing bacterial biofilms, however, its effectiveness is often impeded by the robust physical and chemical defenses of the biofilms. Traditional antibacterial nanoplatforms face challenges in breaching the extracellular polymeric substances barrier to efficiently deliver photosensitizers deep into biofilms. Moreover, the prevalent hypoxia within biofilms restricts the success of oxygen-reliant phototherapy. In this study, we engineered a soft mesoporous organosilica nanoplatform (SMONs) by incorporating polyethylene glycol (PEG), catalase (CAT), and indocyanine green (ICG), forming SMONs-PEG-CAT-ICG (SPCI). We compared the antimicrobial efficacy of SPCI with more rigid nanoplatforms. Our results demonstrated that unique flexible mechanical properties of SPCI enable it to navigate through biofilm barriers, markedly enhancing ICG penetration in methicillin-resistant Staphylococcus aureus (MRSA) biofilms. Notably, in a murine subcutaneous MRSA biofilm infection model, SPCI showed superior biofilm penetration and pharmacokinetic benefits over its rigid counterparts. The embedded catalase in SPCI effectively converts excess H2O2 present in infected tissues into O2, alleviating hypoxia and significantly boosting the antibacterial performance of phototherapy. Both in vitro and in vivo experiments confirmed that SPCI surpasses traditional rigid nanoplatforms in overcoming biofilm barriers, offering improved treatment outcomes for infections associated with bacterial biofilms. This study presents a viable strategy for managing bacterial biofilm-induced diseases by leveraging the unique attributes of a soft mesoporous organosilica-based nanoplatform. STATEMENT OF SIGNIFICANCE: This research introduces an innovative antimicrobial phototherapy soft nanoplatform that overcomes the inherent limitations posed by the protective barriers of bacterial biofilms. By soft nanoplatform with flexible mechanical properties, we enhance the penetration and delivery of photosensitizers into biofilms. The inclusion of catalase within this soft nanoplatform addresses the hypoxia in biofilms by converting hydrogen peroxide into oxygen in infected tissues, thereby amplifying the antibacterial effectiveness of phototherapy. Compared to traditional rigid nanoplatforms, this flexible nanoplatform not only promotes the delivery of therapeutic agents but also sets a new direction for treating bacterial biofilm infections, offering significant implications for future antimicrobial therapies.

Revolution in Cancer Treatment: How Are Intelligently Designed Nanostructures Changing the Game?

Nanoparticles (NPs) are extremely important tools to overcome the limitations imposed by therapeutic agents and effectively overcome biological barriers. Smart designed/tuned nanostructures can be extremely effective for cancer treatment. The selection and design of nanostructures and the adjustment of size and surface properties are extremely important, especially for some precision treatments and drug delivery (DD). By designing specific methods, an important era can be opened in the biomedical field for personalized and precise treatment. Here, we focus on advances in the selection and design of nanostructures, as well as on how the structure and shape, size, charge, and surface properties of nanostructures in biological fluids (BFs) can be affected. We discussed the applications of specialized nanostructures in the therapy of head and neck cancer (HNC), which is a difficult and aggressive type of cancer to treat, to give an impetus for novel treatment approaches in this field. We also comprehensively touched on the shortcomings, current trends, and future perspectives when using nanostructures in the treatment of cancer.

Mn Single-Atom Nanozyme Functionalized 3D-Printed Bioceramic Scaffolds for Enhanced Antibacterial Activity and Bone Regeneration

Infective bone defect is increasingly threatening human health. How to achieve the optimal antibacterial activity and regenerative repair of infective bone defect simultaneously is a huge challenge in clinic. Herein, this work reports a rational integration of Mn single-atom nanozyme into the 3D-printed bioceramic scaffolds (Mn/HSAE@BCP scaffolds). The integrated Mn/HSAE@BCP scaffolds can catalyze the conversion of H2O2 to produce hydroxyl radical (•OH) and superoxide anion (O2 •-) through cascade reaction. Besides, the prominent thermal conversion efficiency of Mn/HSAE@BCP scaffolds can be utilized for sonodynamic therapy (SDT). The synergetic strategy of chemodynamic therapy (CDT)/SDT enables the sufficient generation of reactive oxygen species (ROS) to kill Staphylococcus aureus (S. aureus) or Escherichia coli (E. coli). Furthermore, the enhanced antibacterial efficacy of Mn/HSAE@BCP scaffolds is beneficial to upregulate the expression of osteogenesis-related markers (such as collagen 1(COL1), Runt-related transcription factor 2 (Runx2), osteocalcin (OCN), and osteoprotegerin (OPG)) in vitro and further promote bone regeneration in vivo. The results demonstrate the good potential of Mn/HSAE@BCP scaffolds for the enhanced antibacterial activity and bone regeneration, which provide an effective method for the treatment of clinical infective bone defect.

Recent design strategies for boosting chemodynamic therapy of bacterial infections

The emergence of drug-resistant bacteria poses a significant threat to people's lives and health as bacterial infections continue to persist. Currently, antibiotic therapy remains the primary approach for tackling bacterial infections. However, the escalating rates of drug resistance coupled with the lag in the development of novel drugs have led to diminishing effectiveness of conventional treatments. Therefore, the development of nonantibiotic-dependent therapeutic strategies has become imperative to impede the rise of bacterial resistance. The emergence of chemodynamic therapy (CDT) has opened up a new possibility due to the CDT can convert H2O2 into •OH via Fenton/Fenton-like reaction for drug-resistant bacterial treatment. However, the efficacy of CDT is limited by a variety of practical factors. To overcome this limitation, the sterilization efficiency of CDT can be enhanced by introducing the therapeutics with inherent antimicrobial capability. In addition, researchers have explored CDT-based combined therapies to augment its antimicrobial effects and mitigate its potential toxic side effects toward normal tissues. This review examines the research progress of CDT in the antimicrobial field, explores various strategies to enhance CDT efficacy and presents the synergistic effects of CDT in combination with other modalities. And last, the current challenges faced by CDT and the future research directions are discussed.

Development and performance evaluation of self-assembled pH-responsive curcumin-bacterial exopolysaccharide micellar conjugates as bioactive delivery system

The present study reports the synthesis of micellar conjugates, wherein curcumin (Cur), a bioactive compound with poor bioavailability, was covalently bonded to a bacterial exopolysaccharide (EPS). These conjugates were synthesized by utilizing succinic acid that linked Cur to the pyranosyl moiety of the EPS. The Cur-EPS conjugates appeared as spherical micelles in aqueous solution and were found to have an average hydrodynamic diameter of 254 ± 2.7 nm. The micellar conjugates showed superior stability than Cur as evident from their negative surface charge (-27 ± 1.8 mV) and low polydispersity index (PDI) (0.33 ± 0.04). The in vitro studies on release kinetics helped elucidate the pH-responsive characteristics of the Cur-EPS conjugate, as 87.50 ± 1.45 % of Cur was released at an acidic pH of 5.6, in contrast to 30.15 ± 2.61 % at systemic pH of 7.4 at 150 h. The conjugates were hemocompatible and exhibited cytotoxic effect against the osteosarcoma cell line (MG-63) after 48 h treatment. They also demonstrated superior antibacterial, antibiofilm, and antioxidant activities in comparison to free Cur. Therefore, the Cur-EPS conjugates have potential pharmaceutical applications as therapeutic biomaterial that can be applied as a drug delivery system.

Nanogel-based composites for bacterial antibiofilm activity: advances, challenges, and prospects

Nano-based approaches, particularly nanogels, have recently emerged as a potential strategy for combating biofilm-related infections. Their exceptional characteristics including biocompatibility, biodegradability, stability, high water content, stimuli-responsiveness, and their nano size (which enables their penetration into biofilms) make nanogels a promising technology in the biomedical field. However, exploring nanogels for biofilm treatment remains in its early stages. This review examined the status of nanogels application for the treatment of bacterial biofilms. Recent investigations studied nanogels derived from natural polymers like chitosan (CS), hyaluronic acid (HA), and alginate, among others, for eliminating and inhibiting biofilms. These nanogels were utilized as carriers for diverse antibiofilm agents, encompassing antibiotics, antimicrobial peptides, natural extracts, and nanoparticles. Utilizing mechanisms like conventional antibody-mediated pathways, photodynamic therapy, photothermal therapy, chemodynamic therapy, and EPS degradation, these nanogels effectively administered antibiofilm drugs, exhibiting efficacy across several bacterial strains, notably Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli), among others. Despite showing promise, nanogels remain relatively underexplored in biofilm treatment. This review concludes that research gaps are still present in biofilm treatment processes including (i) a better understanding of the stimuli-responsive behaviors of nanogels, (ii) active targeting strategies, and (iii) the narrow spectrum of antibiofilm agents loaded into nanogels. Hence, future studies could be directed towards the following elements: the exploration of multi-strain biofilms rather than single-strain biofilms, other endogenous and exogenous stimuli to trigger drug release, active targeting mechanisms, a broader range of antibiofilm agents when employing nanogels, and fostering more comprehensive and reliable biofilm treatment strategies. This review found that there are currently several research gaps as well in the use of nanogels for biofilm therapy, and these include: (i) very limited exogenous and endogenous stimuli were explored to trigger drug release from nanogels, (ii) the active targeting strategies were not explored, (iii) a very narrow spectrum of antibiofilm agents was loaded into nanogels, and (iv) only biofilms of single strains were investigated.

pH-responsive polymeric nanomaterials for the treatment of oral biofilm infections

Bacterial and fungal pathogens forming oral biofilms present significant public health challenges due to the failure of antimicrobial drugs. The ability of biofilms to lower pH levels results in dental plaque, leading to gingivitis and cavities. Nanoparticles (NPs) have attracted considerable interest for drug delivery and, thus, as a solution to biofilm-related microbial infections. A novel strategy in this regard involves using pH-responsive polymeric NPs within the acidic microenvironment of oral biofilms. The acidity of the oral biofilm microenvironment is governed by carbohydrate metabolism, accumulation of lactic acid, and extracellular DNA of extracellular polymeric substances by oral biofilm-forming microbial pathogens. This acidity also provides an opportunity to enhance antibacterial activity against biofilm cells using pH-responsive drug delivery approaches. Thus, various polymeric NPs loaded with poorly soluble drugs and responsive to the acidic pH of oral biofilms have been developed. This review focuses on various forms of such polymeric NPs loaded with drugs. The fundamental mechanisms of action of pH-responsive polymeric NPs, their cytological toxicity, and in vivo efficacy testing are thoroughly discussed.

Biocompatible Rhamnolipid Self-Assemblies with pH-Responsive Antimicrobial Activity

There is an urgent need for alternative antimicrobial materials due to the growing challenge of bacteria becoming resistant to conventional antibiotics. This study demonstrates the creation of a biocompatible pH-switchable antimicrobial material by combining bacteria-derived rhamnolipids (RL) and food-grade glycerol monooleate (GMO). The integration of RL into dispersed GMO particles, with an inverse-type liquid crystalline cubic structure in the core, leads to colloidally stable supramolecular materials. The composition and pH-triggered structural transformations are studied with small-angle X-ray scattering, cryogenic transmission electron microscopy, and dynamic light scattering. The composition-structure-activity relationship is analyzed and optimized to target bacteria at acidic pH values of acute wounds. The new RL/GMO dispersions reduce Staphylococcus aureus (S. aureus) populations by 7-log after 24 h of treatment with 64 µg mL-1 of RL and prevent biofilm formation at pH = 5.0, but have no activity at pH = 7.0. Additionally, the system is active against methicillin-resistant S. aureus (MRSA) with minimum inhibitory concentration of 128 µg mL-1 at pH 5.0. No activity is found against several Gram-negative bacteria at pH 5.0 and 7.0. The results provide a fundamental understanding of lipid self-assembly and the design of lipid-based biomaterials, which can further guide the development of alternative bio-based solutions to combat bacteria.

An ultrasound-controllable ROS-responsive nanoplatform for O2 and NO generation to enhance sonodynamic therapy against multidrug-resistant bacterial infections

Antimicrobial sonodynamic therapy (SDT) has broad application potential in the eradication of multidrug-resistant (MDR) bacterial infections due to its non-invasiveness, absence of resistance concern, and high cytotoxicity. However, the hypoxic infection microenvironment and the rapid depletion of O2 during SDT severely limit the therapeutic efficacy of SDT. Herein, an ultrasound-controllable ROS-responsive nanoplatform (FOT/Fe3O4@Lipo-ICG) was constructed and prepared by encapsulating FOT and Fe3O4 nanoparticles (Fe3O4 NPs) within sonosensitiser ICG-modified liposomes. Both in vitro and in vivo, we observed that ICG conjugation on the surface of liposomes could effectively maintain good dispersion and prevent ICG aggregates in complex biological matrices. In addition, liposomes could significantly block the catalytic activity of Fe3O4 NPs, as well as the release of FOT, whereas upon US irradiation, the catalytic activity of Fe3O4 NPs was recovered to catalyse the decomposition of endogenous H2O2 into O2 and ˙OH. Meanwhile, the FOT was successfully released to react with endogenous glutathione to sequentially produce NO. Based on the aforementioned advantages, the FOT/Fe3O4@Lipo-ICG demonstrated potent efficacy in eradicating methicillin-resistant Staphylococcus aureus-induced local infection and sepsis resulting from local infection. Thus, the developed US-controllable nanoplatform offers a promising strategy for enhancing SDT for eradicating MDR bacterial infections.

Antibacterial Chemodynamic Therapy: Materials and Strategies

The wide and frequent use of antibiotics in the treatment of bacterial infection can cause the occurrence of multidrug-resistant bacteria, which becomes a serious health threat. Therefore, it is necessary to develop antibiotic-independent treatment modalities. Chemodynamic therapy (CDT) is defined as the approach employing Fenton and/or Fenton-like reactions for generating hydroxyl radical (•OH) that can kill target cells. Recently, CDT has been successfully employed for antibacterial applications. Apart from the common Fe-mediated CDT strategy, antibacterial CDT strategies mediated by other metal elements such as copper, manganese, cobalt, molybdenum, platinum, tungsten, nickel, silver, ruthenium, and zinc have also been proposed. Furthermore, different types of materials like nanomaterials and hydrogels can be adopted for constructing CDT-involved antibacterial platforms. Besides, CDT can introduce some toxic metal elements and then achieve synergistic antibacterial effects together with reactive oxygen species. Finally, CDT can be combined with other therapies such as starvation therapy, phototherapy, and sonodynamic therapy for achieving improved antibacterial performance. This review first summarizes the advancements in antibacterial CDT and then discusses the present limitations and future research directions in this field, hoping to promote the development of more effective materials and strategies for achieving potentiated CDT.

On-Demand Free Radical Release by Laser Irradiation for Photothermal-Thermodynamic Biofilm Inactivation and Tooth Whitening

Dental diseases associated with biofilm infections and tooth staining affect billions of people worldwide. In this study, we combine photothermal agents (MoS₂@BSA nanosheets, MB NSs), a thermolysis free-radical initiator (AIPH), and carbomer gel to develop laser-responsive hydrogel (MBA-CB Gel) for biofilm inactivating and tooth whitening. Under a physiological temperature without laser irradiation, MB NSs can eliminate free radicals generated from the slow decomposition of AIPH due to their antioxidative activity, thereby avoiding potential side effects. A cytotoxicity study indicates that MB NSs can protect mammalian cells from the free radicals released from AIPH without laser irradiation. Upon exposure to laser irradiation, MB NSs promote the rapid decomposition of AIPH to release free radicals by photothermal effect, suggesting their on-demand release ability of free radicals. In vitro experimental results show that the bacteria inactivation efficiency is 99.91% (3.01 log units) for planktonic Streptococcus mutans (S. mutans) and 99.98% (3.83 log units) for planktonic methicillin-resistant Staphylococcus aureus (MRSA) by the mixed solution of MB NSs and AIPH (MBA solution) under 808 nm laser irradiation (1.0 W/cm², 5 min). For S. mutans biofilms, an MBA solution can inactivate 99.97% (3.63 log units) of the bacteria under similar laser irradiation conditions. Moreover, MBA-CB Gel can whiten an indigo carmine-stained tooth under laser irradiation after 60 min of laser treatment, and the color difference (ΔE) in the teeth of the MBA-CB Gel treatment group was 10.9 times that of the control group. This study demonstrates the potential of MBA-CB Gel as a promising platform for biofilm inactivation and tooth whitening. It is worth noting that, since this study only used stained models of extracted teeth, the research results may not fully reflect the actual clinic situation. Future clinical research needs to further validate these findings.

Design strategy and research progress of multifunctional nanoparticles in lung cancer therapy

INTRODUCTION

Lung cancer is one of the cancer types with the highest mortality rate, exploring a more effective treatment modality that improves therapeutic efficacy while mitigating side effects is now an urgent requirement. Designing multifunctional nanoparticles can be used to overcome the limitations of drugs and conventional drug delivery systems. Nanotechnology has been widely researched, and through different needs, suitable nanocarriers can be selected to load anti-cancer drugs to improve the therapeutic effect. It is foreseeable that with the rapid development of nanotechnology, more and more lung cancer patients will benefit from nanotechnology. This paper reviews the merits of various multifunctional nanoparticles in the treatment of lung cancer to provide novel ideas for lung cancer treatment.

AREAS COVERED

This review focuses on summarizing various nanoparticles for targeted lung cancer therapy and their advantages and disadvantages, using nanoparticles loaded with anti-cancer drugs, delivered to lung cancer sites, enhancing drug half-life, improving anti-cancer drug efficacy and reducing side effects.

EXPERT OPINION

The delivery mode of nanoparticles with superior pharmacokinetic properties in the in vivo circulation enhances the half-life of the drug, and provides tissue-targeted selectivity and the ability to overcome biological barriers, bringing a revolution in the field of oncology.

Nanodroplet-enhanced sonodynamic therapy potentiates immune checkpoint blockade for systemic suppression of triple-negative breast cancer

Immune checkpoint blockade (ICB) has shown great promise in treating various advanced malignancies including triple-negative breast cancer (TNBC). However, only limited number of patients could benefit from it due to the low immune response rate caused by insufficient matured dendritic cells (DCs) and inadequate tumor infiltration of cytotoxic T lymphocytes (CTLs). Here, we report a combination therapeutic strategy which integrates STING pathway activation, hypoxia relief and sonodynamic therapy (SDT) with anti-PD-L1 therapy to improve the therapeutic outcome. The synthesized nanodroplet consisted of a O₂-filled Perfluorohexane (PFH) core and a lipid membrane carrying sonosensitizer IR-780 and STING agonist Vadimezan (DMXAAs). It released O₂ inside the hypoxic tumor tissue, thereby enhancing SDT which relied on O₂ to generate cytotoxic reactive oxygen species (ROS). The co-delivered STING agonist DMXAAs promoted the maturation and tumor antigen cross-presenting of DCs for priming of CTLs. Moreover, SDT induced immunogenic cell death (ICD) of tumor to release abundant tumor-associated antigens, which increased tumor immunogenicity to promote tumor infiltration of CTLs. Consequently, not only a robust adaptive immune response was elicited but also the immunologically "cold" TNBC was turned "hot" to enable a potent anti-PD-L1 therapy. The nanodroplet demonstrated strong efficacy to systemically suppress TNBC growth and mimic distant tumor in vivo. STATEMENT OF SIGNIFICANCE: Only a limited number of triple-negative breast cancer (TNBC) patients can benefit from immune checkpoint blockade therapy due to its low immune response rate caused by insufficient matured DCs and inadequate tumor infiltration of cytotoxic T lymphocytes (CTLs). Interestingly, compelling evidence has shown that sonodynamic therapy (SDT) not only directly kills cancer cells but also elicits immunogenic cell death (ICD), which promotes tumor infiltration of cytotoxic T lymphocytes to transform an immunosuppressive "cold" tumor into a "hot" one. However, the hypoxic tumor microenvironment severely restricts the therapeutic efficiency of SDT, wherein, oxygen is indispensable in the process of ROS generation. Here, we report an O₂-filled nanodroplet-enhanced sonodynamic therapy that significantly potentiated immune checkpoint blockade for systemic suppression of TNBC.

The role of nanocomposites against biofilm infections in humans

The use of nanomaterials in several fields of science has undergone a revolution in the last few decades. It has been reported by the National Institutes of Health (NIH) that 65% and 80% of infections are accountable for at least 65% of human bacterial infections. One of their important applications in healthcare is the use of nanoparticles (NPs) to eradicate free-floating bacteria and those that form biofilms. A nanocomposite (NC) is a multiphase stable fabric with one or three dimensions that are much smaller than 100 nm, or systems with nanoscale repeat distances between the unique phases that make up the material. Using NC materials to get rid of germs is a more sophisticated and effective technique to destroy bacterial biofilms. These biofilms are refractory to standard antibiotics, mainly to chronic infections and non-healing wounds. Materials like graphene and chitosan can be utilized to make several forms of NCs, in addition to different metal oxides. The ability of NCs to address the issue of bacterial resistance is its main advantage over antibiotics. This review highlights the synthesis, characterization, and mechanism through which NCs disrupt Gram-positive and Gram-negative bacterial biofilms, and their relative benefits and drawbacks. There is an urgent need to develop materials like NCs with a larger spectrum of action due to the rising prevalence of human bacterial diseases that are multidrug-resistant and form biofilms.

Emerging nanosonosensitizers augment sonodynamic-mediated antimicrobial therapies

With the widespread prevalence of drug-resistant pathogens, traditional antibiotics have limited effectiveness and do not yield the desired outcomes. Recently, alternative antibacterial therapies based on ultrasound (US) have been explored to overcome the crisis of bacterial pathogens. Antimicrobial sonodynamic therapy (aSDT) offers an excellent solution that relies on US irradiation to produce reactive oxygen species (ROS) and achieve antibiotic-free mediated antimicrobial effects. In addition, aSDT possesses the advantage of superior tissue penetrability of US compared to light irradiation, demonstrating great feasibility in treating deep infections. Although existing conventional sonosensitizers can produce ROS for antimicrobial activity, some limitations, such as low penetration rate, nonspecific distribution and poor ROS production under hypoxic conditions, result in suboptimal sterilization in aSDT. Recently, emerging nanosonosensitizers have enormous advantages as high-performance agents in aSDT, which overcome the deficiencies of conventional sonosensitizers as described above. Thus, nanosonosensitizer-mediated aSDT has a bright future for the management of bacterial infections. This review classifies the current available nanosonosensitizers and provides an overview of the mechanisms, biomedical applications, recent advances and perspectives of aSDT.

GSH-depleting and H2O2-self-supplying hybrid nanozymes for intensive catalytic antibacterial therapy by photothermal-augmented co-catalysis

Nanozyme-based chemodynamic therapy (CDT) has shown tremendous potential in the treatment of bacterial infections. However, the CDT antibacterial efficacy is severely limited by the catalytic activity of nanozymes or the infection microenvironments such as insufficient hydrogen peroxide (H₂O₂) and overexpressed glutathione (GSH). Herein, a versatile hybrid nanozyme (MoS₂/CuO₂) is rationally constructed by simply decorating ultrasmall CuO₂ nanodots onto lamellar MoS₂ platelets of hydrangea-like MoS₂ nanocarrier via a covalent Cu-S bond. The MoS₂/CuO₂ nanozyme exhibits the peroxidase-mimic activity for catalytically converting H₂O₂ produced by acid-triggered decomposition of the decorated CuO₂ into hydroxyl radical (•OH). Meanwhile, the MoS₂/CuO₂ can consume GSH overexpressed in the infection sites via redox reaction mediated by polyvalent transition metal ions (Cu²⁺ and Mo⁶⁺) for enhanced CDT. More importantly, MoS₂ support can promote the conversion of Cu²⁺ to Cu⁺ by a co-catalytic reaction based on the Mo⁴⁺/Mo⁶⁺ redox couples, and provide photonic hyperthermia (PTT) to augment the peroxidase-mimic activity. The developed MoS₂/CuO₂ nanozymes possesses a desirable catalytic property, as well as a remarkably improved antibacterial efficiency both in vitro and in vivo. Taken together, this study proposes a synergetic multiple enhancement strategy to successfully construct the versatile hybrid nanozymes for intensive in vivo PTT/CDT dual-mode anti-infective therapy. STATEMENT OF SIGNIFICANCE: Chemodynamic therapy (CDT) has shown great potentialities in the treatment of bacterial infections, while its therapeutic efficiency is severely limited by the infection microenvironments such as insufficient hydrogen peroxide (H₂O₂) and overexpressed glutathione (GSH). Here, we rationally construct a hybrid nanozyme (MoS₂/CuO₂) with peroxidase-like activity that can enhance CDT by regulating local microenvironments, that is, simultaneously self-supplying H₂O₂ and consuming GSH. Importantly, MoS₂ support can promote the conversion of Cu²⁺ to Cu⁺ by the Mo⁴⁺/Mo⁶⁺ redox couples, and provide photonic hyperthermia (PTT) to augment the peroxidase-mimic activity. The developed MoS₂/CuO₂ shows desirable PTT/CDT dual-mode antibacterial efficacy both in vitro and in vivo. This study proposes a versatile hybrid nanozyme with multiple enhancement effects for intensive in vivo anti-infective therapy.

Riboflavin-Promoted In Situ Photoactivation of Dihydroalkaloid Prodrugs for Cancer Therapy

Cancer therapies usually suffer from poor targeting ability and serious side effects. Photoactivatable cancer therapy has the significant advantage of a high spatiotemporal resolution, but most photoactivatable prodrugs require decoration with stoichiometric photocleavable groups, which are only responsive to ultraviolet irradiation and suffer from low reaction efficiency. To tackle these challenges, we herein propose a photoactivation strategy with biogenic riboflavin as the photosensitizer to promote the in situ transformation of noncytotoxic dihydroalkaloid prodrugs dihydrochelerythrine (DHCHE), dihydrosanguinarine (DHSAN), and dihydronitidine (DHNIT) into anticancer alkaloid drugs chelerythrine (CHE), sanguinarine (SAN), and nitidine (NIT), respectively, which can efficiently kill cancer cells and inhibit in vivo tumor growth. Meanwhile, the photoactivatable transformation can be in situ monitored by green-to-red fluorescence conversion, which will contribute to easy controlling of the therapeutic dose. The proposed photoactivatable transformation mechanism was also explored by density functional theory (DFT) calculations. We believe this riboflavin-promoted and imaging-guided photoactivation strategy is promising for precise cancer therapy.

Synergy between pH- and hypoxia-responsiveness in antibiotic-loaded micelles for eradicating mature, infectious biofilms

Antibiotic-loaded PEG/PAE-based micelles are frequently considered for eradicating infectious biofilms. At physiological pH, PEG facilitates transport through blood. Near an acidic infection-site, PAE becomes protonated causing micellar targeting to a biofilm. However, micellar penetration and accumulation is confined to the surface region of a biofilm. Especially matured biofilms also possess hypoxic regions. We here designed dual-responsive PEG/PAE-b-P(Lys-NBCF) micelles, responding to both acidity and low oxygen-saturation level in matured biofilms. Dual, pH- and hypoxia-responsive micelles targeted and accumulated evenly over the depth of 7- to 14-days old biofilms. Delineation demonstrated that pH-responsiveness was responsible for targeting of the infection-site and accumulation of micelles in the surface region of the biofilm. Hypoxia-responsiveness caused deep penetration in the biofilm. Dual, pH- and hypoxia-responsive micelles loaded with ciprofloxacin yielded more effective, synergistic eradication of 10-days old, matured Staphylococcus aureus biofilms underneath an abdominal imaging-window in living mice than achieved by ciprofloxacin in solution or single, pH- or hypoxia responsive micelles loaded with ciprofloxacin. Also, wound-healing after removal of window and its frame proceeded fastest after tail-vein injection of ciprofloxacin-loaded, dual, pH- and hypoxia-responsive micelles. Concluding, pH- and hypoxia-responsiveness are both required for eradicating mature biofilms and advancing responsive antibiotic nanocarriers to clinical application. STATEMENT OF SIGNIFICANCE: pH-responsive antibiotic nanocarriers have emerged as a possible new strategy to prevent antimicrobial-resistant bacterial infections from becoming the leading cause of death. In this paper, we show that commonly studied, pH-responsive micellar nanocarriers merely allow self-targeting to an infectious biofilm, but do not penetrate deeply into the biofilm. The dual-responsive (acidic pH- and hypoxia) antibiotic-loaded micelles designed here not only self-target to an infectious biofilm, but also penetrate deeply. The in vitro and in vivo advantages of dual-responsive nanocarriers are most obvious when studied in infectious biofilms grown for 10 viz a viz the 2 days, usually applied in the literature. Significantly, clinical treatment of bacterial infection usually starts more than 2 days after appearance of the first symptoms.

Biomimetic electrodynamic nanoparticles comprising ginger-derived extracellular vesicles for synergistic anti-infective therapy

Nanotechnology enlightens promising antibacterial strategies while the complex in vivo infection environment poses a great challenge to the rational design of nanoplatforms for safe and effective anti-infective therapy. Herein, a biomimetic nanoplatform (EV-Pd-Pt) integrating electrodynamic Pd-Pt nanosheets and natural ginger-derived extracellular vesicles (EVs) is proposed. The introduction of ginger-derived EVs greatly endows EV-Pd-Pt with prolonged blood circulation without immune clearance, as well as accumulation at infection sites. More interestingly, EV-Pd-Pt can enter the interior of bacteria in an EV lipid-dependent manner. At the same time, reactive oxygen species are sustainably generated in situ to overcome the limitations of their short lifetime and diffusion distance. Notably, EV-Pd-Pt nanoparticle-mediated electrodynamic and photothermal therapy exhibit synergistic effects. Furthermore, the desirable biocompatibility and biosafety of the proposed nanoplatform guarantee the feasibility of in vivo applications. This proof-of-concept work holds significant promise for developing biomimetic nanoparticles by exploiting their intrinsic properties for synergistic anti-infective therapy.

Facile construction of fluorescent C70-COOH nanoparticles with advanced antibacterial and anti-biofilm photodynamic activity

Photodynamic antibacterial therapy has been considered as one of the most promising treatments to alleviate the spread of multidrug resistant bacterial pathogens. Given the hypoxic environment of infectious tissues, photosensitizers with reduced oxygen-demand could exhibit superiority upon irradiation. Herein reported is a novel C₇₀-based photosensitizers synthesized by the facile one-step thiol-ene reaction. Various characterization techniques were employed to confirm the structural, photoluminescent properties, photostability and biocompatibility of the as-synthesized C₇₀-COOH nanoparticles. Furthermore, they were capable of efficiently producing reactive oxygen species following both the type I and II mechanistic pathways, thus still generating adequate free radicals under hypoxic condition. Therefore, they could approach and destroy the bacterial cell membrane in the presence of visible light, thereby causing cytoplasmic leakage and eventually achieving broad-spectrum inactivation of four representative bacterial strains. Especially, methicillin-resistant Staphylococcus aureus (MRSA) were completely eliminated after merely 10 minutes irradiation, and the formation of its corresponding biofilm were also greatly inhibited by C₇₀-COOH nanoparticles. These results provide new insights and opportunities for the development of hypoxia-tolerant fullerene-based photosensitizers to combat multidrug resistant bacterial and related infections.

Cuprous Oxide Nanoparticles Decorated Fabric Materials with Anti-biofilm Properties

Considering the global spread of bacterial infections, the development of anti-biofilm surfaces with high antimicrobial activities is highly desired. This work unraveled a simple, sonochemical method for coating Cu2O nanoparticles (NPs) on three different flexible substrates: polyester (PE), nylon 2 (N2), and polyethylene (PEL). The introduction of Cu2O NPs on these substrates enhanced their surface hydrophobicity, induced ROS generation, and completely inhibited the growth of sensitive (Escherichia coli and Staphyloccocus aureus) and drug-resistant (MDR E. coli and MRSA) planktonic and biofilm. The experimental results confirmed that Cu2O-PE exhibited complete biofilm mass reduction ability for all four strains, whereas Cu2O-N2 showed more than 99% biomass inhibition against both drug-resistant and sensitive pathogens in 6 h. Moreover, Cu2O-PEL also indicated a 99.95, 97.73, 98.00, and 99.20% biomass reduction of MRSA, MDR E. coli, E. coli, and S. aureus, respectively. All substrates were investigated for time-dependent inhibitions, and the associated biofilm mass and log reduction were evaluated. The mechanisms of Cu2O NP action against the mature biofilms include the generation of reactive oxygen species (ROS) as well as electrostatic interaction between Cu2O NPs and bacterial membranes. The current study could pave the way for the commercialization of sonochemically coated Cu2O NP flexible substrates for the prevention of microbial contamination in hospitals and industrial environments.

Self-locomotive, antimicrobial microrobot (SLAM) swarm for enhanced biofilm elimination

Biofilm is a major cause of infections and infrastructure deterioration, largely due to molecular diffusion restrictions that hamper the antimicrobial activity of traditional antibiotics and disinfectants. Here, we present a self-locomotive, antimicrobial microrobot (SLAM) swarm that can penetrate, fracture, and detach biofilm and, in turn, nullify bacterial resistance to antibiotics. The SLAM is assembled by loading a controlled mass of manganese oxide nanosheets on diatoms with the polydopamine binder. In hydrogen peroxide solution, SLAMs produce oxygen bubbles that generate thrust to penetrate the rigid and dense Pseudomonas aeruginosa biofilm and self-assemble into a swarm that repeatedly surrounds, expands, and bursts oxygen bubbles. The resulting cavities continue to deform and fracture extracellular polymeric substances from microgrooved silicone substrates and wounded skin explants while decreasing the number of viable bacterial cells. Additionally, SLAM allows irrigating water or antibiotics to access the residual biofilm better, thus enhancing the synergistic efficacy in killing up to 99.9% of bacterial cells.

Nanoparticles in Endodontics Disinfection: State of the Art

Endodontic-related diseases constitute the fourth most expensive pathologies in industrialized countries. Specifically, endodontics is the part of dentistry focused on treating disorders of the dental pulp and its consequences. In order to treat these problems, especially endodontic infections, dental barriers and complex root canal anatomy should be overcome. This constitutes an unmet medical need since the rate of successful disinfection with the currently marketed drugs is around 85%. Therefore, nanoparticles constitute a suitable alternative in order to deliver active compounds effectively to the target site, increasing their therapeutic efficacy. Therefore, in the present review, an overview of dental anatomy and the barriers that should be overcome for effective disinfection will be summarized. In addition, the versatility of nanoparticles for drug delivery and their specific uses in dentistry are comprehensively discussed. Finally, the latest findings, potential applications and state of the art nanoparticles with special emphasis on biodegradable nanoparticles used for endodontic disinfection are also reviewed.

Potentiating hypoxic microenvironment for antibiotic activation by photodynamic therapy to combat bacterial biofilm infections

Traditional antibiotic treatment has limited efficacy for the drug-tolerant bacteria present in biofilms because of their unique metabolic conditions in the biofilm infection microenvironment. Modulating the biofilm infection microenvironment may influence the metabolic state of the bacteria and provide alternative therapeutic routes. In this study, photodynamic therapy is used not only to eradicate methicillin-resistant Staphylococcus aureus biofilms in the normoxic condition, but also to potentiate the hypoxic microenvironment, which induces the anaerobic metabolism of methicillin-resistant Staphylococcus aureus and activates the antibacterial activity of metronidazole. Moreover, the photodynamic therapy-activated chemotherapy can polarize the macrophages to a M2-like phenotype and promote the repair of the biofilm infected wounds in mice. This biofilm infection microenvironment modulation strategy, whereby the hypoxic microenvironment is potentiated to synergize photodynamic therapy with chemotherapy, provides an alternative pathway for efficient treatment of biofilm-associated infections.

Bacteria in biofilms present unique metabolic conditions that limit the traditional antibiotic treatment. Here, the authors show a photodynamic therapy-activated chemotherapy potentiating the hypoxia of biofilms of methicillin-resistant Staphylococcus aureus, by developing hyaluronic acid nanoparticles functionalized with chlorin e6 and metronidazole.

NIR-activated nanosystems with self-modulated bacteria targeting for enhanced biofilm eradication and caries prevention

The efficacious delivery of antimicrobial drugs to intractable oral biofilms remains a challenge due to inadequate biofilm penetration and lack of pathogen targeting. Herein, we have developed a microenvironment-activated poly(ethylene glycol) (PEG)-sheddable nanoplatform to mediate targeted delivery of drugs into oral biofilms for the efficient prevention of dental caries. The PEGylated nanoplatform with enhanced biofilm penetration is capable of deshielding the PEG layer under slightly acidic conditions in a PEG chain length-dependent manner to re-expose the bacteria-targeting ligands, thereby facilitating targeted codelivery of ciprofloxacin (CIP) and IR780 to the bacteria after accumulation within biofilms. The nanoplatform tends to induce bacterial agglomeration and suffers from degradation in the acidic oral biofilm microenvironment, triggering rapid drug release on demand around bacterial cells. The self-modulating nanoplatform under near-infrared (NIR) irradiation accordingly displays greatly augmented potency in oral biofilm penetration and disruption compared with drugs alone. Topical oral treatment with nanoplatforms involving synergetic pharmacological and photothermal/photodynamic trinary therapy results in robust biofilm dispersion and efficacious suppression of severe tooth decay in rats. This versatile nanoplatform can promote local accumulation and specific drug transport into biofilms and represents a new paradigm for targeted drug delivery for the management of oral biofilm-associated infections.

Simultaneous Photodynamic Eradication of Tooth Biofilm and Tooth Whitening with an Aggregation-Induced Emission Luminogen

Dental caries is among the most prevalent dental diseases globally, which arises from the formation of microbial biofilm on teeth. Besides, tooth whitening represents one of the fastest-growing areas of cosmetic dentistry. It will thus be great if tooth biofilm eradication can be combined with tooth whitening. Herein, a highly efficient photodynamic dental therapy strategy is reported for tooth biofilm eradication and tooth discoloration by employing a photosensitizer (DTTPB) with aggregation-induced emission characteristics. DTTPB can efficiently inactivate S. mutans, and inhibit biofilm formation by suppressing the expression of genes associated with extracellular polymeric substance synthesis, bacterial adhesion, and superoxide reduction. Its inhibition performance can be further enhanced through combined treatment with chlorhexidine. Besides, DTTPB exhibits an excellent tooth-discoloration effect on both colored saliva-coated hydroxyapatite and clinical teeth, with short treatment time (less than 1 h), better tooth-whitening performance than 30% hydrogen peroxide, and almost no damage to the teeth. DTTPB also demonstrates excellent biocompatibility with neglectable hemolysis effect on mouse red blood cells and almost no killing effect on mammalian cells, which enables its potential applications for simultaneous tooth biofilm eradication and tooth whitening in clinical dentistry.

Oxygen-carrying biomimetic nanoplatform for sonodynamic killing of bacteria and treatment of infection diseases

Among various novel antimicrobial therapies, sonodynamic therapy (SDT) exhibits its advantages for the treatment of bacterial infections due to its high penetration depth and low side effects. In this study, a new nanosonosensitizer (HFH@ZIF-8) that loads sonosensitizer hematoporphyrin monomethyl ether (HMME) into zeolitic imidazolate framework-8 (ZIF-8), was constructed for killing multidrug-resistant (MDR) bacteria and treatment of in vivo infection diseases by SDT. In particular, the developed HFH@ZIF-8 exhibited enhanced water-solubility, good biocompatibility, and improved disease-targeting capability for delivering and releasing HMME and ablating the infected lesion. More importantly, the presence of oxygen-carrying hemoglobin for HFH@ZIF-8 can offer sufficient oxygen consumption by SDT, augmenting the efficacy of SDT by improving ROS generating efficiency against deep tissue multidrug-resistant bacterial infection. Therefore, this study paves a new avenue for treating infection disease, particularly for antibiotic resistant bacterial infection.

pH-Responsive Fluorescent Polymer-Drug System for Real-Time Detection and In Situ Eradication of Bacterial Biofilms

Bacterial biofilms encased in extracellular polymeric substances to create protected microenvironments are typically challenging to disperse by common antibiotics and cannot be in situ visualized under current modalities. Herein, a pH-responsive branched polymer [poly(MBA-AEPZ)-AEPZ-NA] capable of overcoming antibiotic resistance and real-time visualizing biofilms for fluorescence imaging-guided infection control is reported. The positively charged polymer can effectively penetrate bacterial biofilms, neutralize the anionic character, and then disrupt the structural integrity, thus significantly promoting the transport of antibiotics into biofilms. The polymer shows a weak fluorescence emission intensity under physiological conditions (pH 7.4) but emits intense green-light emission within the localized biofilm microenvironment (pH 5.5) to real-time visualize bacterial biofilms. A therapeutic system made of the polymer and a model antibiotic can significantly reduce the dosages of the drug, thereby minimizing biofilm-induced drug resistance. Notably, a green fluorescent polymer responding to localized pH conditions is demonstrated in living zebrafish. This work confirmed that combinations of the pH-responsive branched polymer and antibiotics could be administered to overcome drug resistance and realize fluorescence imaging-guided treatment of bacterial biofilm infections.

Chemodynamic Therapy via Fenton and Fenton-Like Nanomaterials: Strategies and Recent Advances

Chemodynamic therapy (CDT), a novel cancer therapeutic strategy defined as the treatment using Fenton or Fenton-like reaction to produce •OH in the tumor region, was first proposed by Bu, Shi, and co-workers in 2016. Recently, with the rapid development of Fenton and Fenton-like nanomaterials, CDT has attracted tremendous attention because of its unique advantages: 1) It is tumor-selective with low side effects; 2) the CDT process does not depend on external field stimulation; 3) it can modulate the hypoxic and immunosuppressive tumor microenvironment; 4) the treatment cost of CDT is low. In addition to the Fe-involved CDT strategies, the Fenton-like reaction-mediated CDT strategies have also been proposed, which are based on many other metal elements including copper, manganese, cobalt, titanium, vanadium, palladium, silver, molybdenum, ruthenium, tungsten, cerium, and zinc. Moreover, CDT has been combined with other therapies like chemotherapy, radiotherapy, phototherapy, sonodynamic therapy, and immunotherapy for achieving enhanced anticancer effects. Besides, there have also been studies that extend the application of CDT to the antibacterial field. This review introduces the latest advancements in the nanomaterials-involved CDT from 2018 to the present and proposes the current limitations as well as future research directions in the related field.

Immunometabolism in biofilm infection: lessons from cancer

BACKGROUND

Biofilm is a community of bacteria embedded in an extracellular matrix, which can colonize different human cells and tissues and subvert the host immune reactions by preventing immune detection and polarizing the immune reactions towards an anti-inflammatory state, promoting the persistence of biofilm-embedded bacteria in the host.

MAIN BODY OF THE MANUSCRIPT

It is now well established that the function of immune cells is ultimately mediated by cellular metabolism. The immune cells are stimulated to regulate their immune functions upon sensing danger signals. Recent studies have determined that immune cells often display distinct metabolic alterations that impair their immune responses when triggered. Such metabolic reprogramming and its physiological implications are well established in cancer situations. In bacterial infections, immuno-metabolic evaluations have primarily focused on macrophages and neutrophils in the planktonic growth mode.

CONCLUSION

Based on differences in inflammatory reactions of macrophages and neutrophils in planktonic- versus biofilm-associated bacterial infections, studies must also consider the metabolic functions of immune cells against biofilm infections. The profound characterization of the metabolic and immune cell reactions could offer exciting novel targets for antibiofilm therapy.

Combination and nanotechnology based pharmaceutical strategies for combating respiratory bacterial biofilm infections

Respiratory infections are one of the major global health problems. Among them, chronic respiratory infections caused by biofilm formation are difficult to treat because of both drug tolerance and poor drug penetration into the complex biofilm structure. A major part of the current research on combating respiratory biofilm infections have been focused on destroying the matrix of extracellular polymeric substance and eDNA of the biofilm or promoting the penetration of antibiotics through the extracellular polymeric substance via delivery technologies in order to kill the bacteria inside. There are also experimental data showing that certain inhaled antibiotics with simple formulations can effectively penetrate EPS to kill surficially located bacteria and centrally located dormant bacteria or persisters. This article aims to review recent advances in the pharmaceutical strategies for combating respiratory biofilm infections with a focus on nanotechnology-based drug delivery approaches. The formation and characteristics of bacterial biofilm infections in the airway mucus are presented, which is followed by a brief review on the current clinical approaches to treat respiratory biofilm infections by surgical removal and antimicrobial therapy, and also the emerging clinical treatment approaches. The current combination of antibiotics and non-antibiotic adjuvants to combat respiratory biofilm infections are also discussed.

Self-targeting of zwitterion-based platforms for nano-antimicrobials and nano-carriers

Self-targeting antimicrobial platforms have yielded new possibilities for the treatment of infectious biofilms. Self-targeting involves stealth transport through the blood circulation towards an infectious biofilm, where the antimicrobial platform penetrates...

A Bone-Targeting Enoxacin Delivery System to Eradicate Staphylococcus Aureus-Related Implantation Infections and Bone Loss

Post-operative infections in orthopaedic implants are severe complications that require urgent solutions. Although conventional antibiotics limit bacterial biofilm formation, they ignore the bone loss caused by osteoclast formation during post-operative orthopaedic implant-related infections. Fortunately, enoxacin exerts both antibacterial and osteoclast inhibitory effects, playing a role in limiting infection and preventing bone loss. However, enoxacin lacks specificity in bone tissue and low bioavailability-related adverse effects, which hinders translational practice. Here, we developed a nanosystem (Eno@MSN-D) based on enoxacin (Eno)-loaded mesoporous silica nanoparticles (MSN), decorated with the eight repeating sequences of aspartate (D-Asp8), and coated with polyethylene glycol The release results suggested that Eno@MSN-D exhibits a high sensitivity to acidic environment. Moreover, this Eno@MSN-D delivery nanosystem exhibited both antibacterial and anti-osteoclast properties in vitro. The cytotoxicity assay revealed no cytotoxicity at the low concentration (20 μg/ml) and Eno@MSN-D inhibited RANKL-induced osteoclast differentiation. Importantly, Eno@MSN-D allowed the targeted release of enoxacin in infected bone tissue. Bone morphometric analysis and histopathology assays demonstrated that Eno@MSN-D has antibacterial and antiosteoclastic effects in vivo, thereby preventing implant-related infections and bone loss. Overall, our study highlights the significance of novel biomaterials that offer new alternatives to treat and prevent orthopaedic Staphylococcus aureus-related implantation infections and bone loss.

Stimuli-Responsive Nanoplatform-Assisted Photodynamic Therapy Against Bacterial Infections

Bacterial infections are common diseases causing tremendous deaths in clinical settings. It has been a big challenge to human beings because of the antibiotics abuse and the newly emerging microbes. Photodynamic therapy (PDT) is a reactive oxygen species-based therapeutic technique through light-activated photosensitizer (PS). Recent studies have highlighted the potential of PDT as an alternative method of antibacterial treatment for its broad applicability and high efficiency. However, there are some shortcomings due to the low selectivity and specificity of PS. Growing evidence has shown that drug delivery nanoplatforms have unique advantages in enhancing therapeutic efficacy of drugs. Particularly, stimuli-responsive nanoplatforms, as a promising delivery system, provide great opportunities for the effective delivery of PS. In the present mini-review, we briefly introduced the unique microenvironment in bacterial infection tissues and the application of PDT on bacterial infections. Then we review the stimuli-responsive nanoplatforms (including pH-, enzymes-, redox-, magnetic-, and electric-) used in PDT against bacterial infections. Lastly, some perspectives have also been proposed to further promote the future developments of antibacterial PDT.

Recent advances in active targeting of nanomaterials for anticancer drug delivery

One of the challenges in cancer chemotherapy is the low target to non-target ratio of therapeutic agents which incur severe adverse effect on the healthy tissues. In this regard, nanomaterials have tremendous potential for impacting cancer therapy by altering the toxicity profile of the drug. Some of the striking advantages provided by the nanocarriers mediated targeted drug delivery are relatively high build-up of drug concentration at the tumor site, improved drug content in the formulation and enhanced colloidal stability. Further, nanocarriers with tumor-specific moieties can be targeted to the cancer cell through cell surface receptors, tumor antigens and tumor vasculatures with high affinity and accuracy. Moreover, it overcomes the bottleneck of aimless drug biodistribution, undesired toxicity and heavy dosage of administration. This review discusses the recent developments in active targeting of nanomaterials for anticancer drug delivery through cancer cell surface targeting, organelle specific targeting and tumor microenvironment targeting strategies. Special emphasis has been given towards cancer cell surface and organelle specific targeting as delivery of anticancer drugs through these routes have made paradigm change in cancer management. Further, the current challenges and future prospects of nanocarriers mediated active drug targeting are also demonstrated.

Simultaneous inhibition of planktonic and biofilm bacteria by self-adapting semiconducting polymer dots

Biofilm infections present an enormous challenge in today's healthcare settings. Currently, pH-switchable antibacterial agents are being developed to eradicate biofilms. However, most pH-switchable antibacterial agents are less lethal to planktonic bacteria under neutral conditions, and cannot prevent the dispersed bacteria from seeding acute infection again. Herein, this work reports the applications of semiconducting polymer dots (Pdots) with a double adhesion mechanism in imaging and inhibiting bacteria inside (weak acidic conditions) and outside (neutral conditions) biofilms. Clew-like Pdots were prepared by covalently linking phenylboronic acid (PBA) and pH-responsive naphthalimide (NA) ramification in semiconducting polymers. Under neutral conditions, the Pdots combined with bacteria through the formation of boronate esters between PBA and diols. Under weakly acidic conditions, the partial borate bond fractured, and the Pdots adhered onto the bacterial surface through the positively charged NA in Pdots. Furthermore, the Pdots display negligible toxicity to mammalian cells and tissues. More importantly, the Pdots can selectively damage the bacterial membrane and inhibit bacteria in vivo. This work highlights the feasibility of using semiconducting Pdots to image and inhibit bacteria inside and outside biofilms, which represents a highly effective strategy to cope with biofilm infections.

Liposomes with Water as a pH-Responsive Functionality for Targeting of Acidic Tumor and Infection Sites

A lipid named DCPA was synthesized under microwave-assisted heating. DCPA possesses a pyridine betaine, hydrophilic group that can be complexed with water through hydrogen bonding (DCPA-H2 O). DCPA-H2 O liposomes became protonated relatively fast already at pH<6.8, due to the high HOMO binding energy of DCPA-H2 O. In murine models, DCPA-H2 O liposomes had longer blood circulation times than natural DPPC or cationic DCPM liposomes, while after tail-vein injection DCPA-H2 O liposomes targeted faster to solid tumors and intra-abdominal infectious biofilms. Therapeutic efficacy in a murine, infected wound-healing model of tail-vein injected ciprofloxacin-loaded DCPA-H2 O liposomes exceeded the ones of clinically applied ciprofloxacin as well as of ciprofloxacin-loaded DPPC or DCPM liposomes.

Biocatalytic Nanomaterials: A New Pathway for Bacterial Disinfection

Clinical treatment of pathogenic infection has emerged as a growing challenge in global public health. Such treatment is currently limited to antibiotics, but abuse of antibiotics have induced multidrug resistance and high fatality rates in anti-infection therapies. Thus, it is vital to develop alternative bactericidal agents to open novel disinfection pathways. Drawing inspiration from elements of the human immune system that show great potential for controlling pathogens or regulating cell apoptosis, the design of biocatalytic nanomaterials (BCNs) have provided unrivaled opportunities for future antibacterial therapies. More significantly, BCNs exhibit various superior properties to immune cells and natural enzymes, such as higher biocatalytic performance, extraordinary stability against harsh conditions, and scalable production. In this review, the most recent efforts toward developing BCN-based biomedical applications in combating bacterial infections are focused upon. BCNs' antibacterial mechanisms, the classification of BCNs, antibacterial activities that can be triggered or augmented by energy conversion, and the eradication of biofilms with BCNs are systematically introduced and discussed. The current challenges and prospects of BCNs for biocatalytic disinfection are also summarized. It is anticipated this review will provide new therapeutic insights into combating bacteria and biofilms and offer significant new inspiration for designing future biocatalytic nanomaterials.

A multifunctional Fenton nanoagent for microenvironment-selective anti-biofilm and anti-inflammatory therapy

Bacterial biofilm infections are intractable to traditional antibiotic treatment and usually cause persistent inflammation. Chemodynamic therapy (CDT) based on the Fenton reaction has recently emerged as a promising anti-biofilm strategy. However, the therapeutic efficacy of current Fenton agents often suffers from inefficient Fenton activity and lacks anti-inflammatory capability. Herein, FePS₃ nanosheets (NSs) are explored for the first time as novel microenvironment-selective therapeutic nanoagents for bacterial biofilm infections with both self-enhanced Fenton activity for an anti-biofilm effect and reactive oxygen species (ROS) scavenging properties for an anti-inflammatory effect. In biofilms with acidic microenvironments, FePS₃ NSs release Fe²⁺ to generate toxic ROS by Fenton reaction and reductive [P₂S₆]^4- to enhance the Fenton activity by reducing Fe³⁺ to Fe²⁺. In the surrounding normal tissues with neutral pH, FePS₃ NSs scavenge ROS by reductive [P₂S₆]^4- with an anti-inflammatory effect. This work demonstrates multifunctional Fenton nanoagents with microenvironment-selective ROS generation and elimination properties for effective treatment of bacterial biofilm infections with both anti-biofilm and anti-inflammatory effects.

Preparation and antitumor evaluation of hinokiflavone hybrid micelles with mitochondria targeted for lung adenocarcinoma treatment

Hinokiflavone (HF) is a natural biflavonoid extracted from medicinal plants such as Selaginella tamariscina and Platycladus orientalis. HF plays a crucial role in the treatment of several cancers. However, its poor solubility, instability, and low bioavailability have limited its use. In this study, soluplus/d-α-tocopherol acid polyethylene glycol 1000 succinate (TPGS)/dequalinium (DQA) was applied to improve the solubilization efficiency and stability of HF. HF hybrid micelles were prepared via thin-film hydration method. The physicochemical properties of micelles, including particle size, zeta potential, encapsulation efficiency, drug loading, CMC value, and stability were investigated. The in vitro cytotoxicity assay showed that the cytotoxicity of the HF hybrid micelles was higher than that of free HF. In addition, the HF hybrid micelles improved anticancer efficacy and induced mitochondria-mediated apoptosis, which is associated with the high levels of ROS inducing decreased mitochondrial membrane potential, promoting apoptosis of tumor cells. Furthermore, in vivo tumor suppression, smaller tumor volume and increased expression of pro-apoptotic proteins were found in nude mice treated with HF hybrid micelles, suggesting that HF hybrid micelles had stronger tumor suppressive activity compared with free HF. In summary, HF hybrid micelles developed in this study enhanced antitumor effect, which may be a potential drug delivery system for the treatment of lung adenocarcinoma.

Impact of the antibiotic-cargo from MSNs on Gram-positive and Gram-negative bacterial biofilms

Mesoporous silica nanoparticles (MSNs) are promising drug nanocarriers for infection treatment. Many investigations have focused on evaluating the capacity of MSNs to encapsulate antibiotics and release them in a controlled fashion. However, little attention has been paid to determine the antibiotic doses released from these nanosystems that are effective against biofilm during the entire release time. Herein, we report a systematic and quantitative study of the direct effect of the antibiotic-cargo released from MSNs on Gram-positive and Gram-negative bacterial biofilms. Levofloxacin (LVX), gentamicin (GM) and rifampin (RIF) were separately loaded into pure-silica and amino-modified MSNs. This accounts for the versatility of these nanosystems since they were able to load and release different antibiotic molecules of diverse chemical nature. Biological activity curves of the released antibiotic were determined for both bacterial strains, which allowed to calculate the active doses that are effective against bacterial biofilms. Furthermore, in vitro biocompatibility assays on osteoblast-like cells were carried out at different periods of times. Albeit a slight decrease in cell viability was observed at the very initial stage, due to the initial burst antibiotic release, the biocompatibility of these nanosystems is evidenced since a recovery of cell viability was achieved after 72 h of assay. Biological activity curves for GM released from MSNs exhibited sustained patterns and antibiotic doses in the 2-6 μg/mL range up to 100 h, which were not enough to eradicate biofilm. In the case of LVX and RIF first-order kinetics featuring an initial burst effect followed by a sustained release above the MIC up to 96 h were observed. Such doses reduced by 99.9% bacterial biofilm and remained active up to 72 h with no emergence of bacterial resistance. This pioneering research opens up promising expectations in the design of personalized MSNs-based nanotherapies to treat chronic bone infection.

Impact of the antibiotic-cargo from MSNs on Gram-positive and Gram-negative bacterial biofilms

Mesoporous silica nanoparticles (MSNs) are promising drug nanocarriers for infection treatment. Many investigations have focused on evaluating the capacity of MSNs to encapsulate antibiotics and release them in a controlled fashion. However, little attention has been paid to determine the antibiotic doses released from these nanosystems that are effective against biofilm during the entire release time. Herein, we report a systematic and quantitative study of the direct effect of the antibiotic-cargo released from MSNs on Gram-positive and Gram-negative bacterial biofilms. Levofloxacin (LVX), gentamicin (GM) and rifampin (RIF) were separately loaded into pure-silica and amino-modified MSNs. This accounts for the versatility of these nanosystems since they were able to load and release different antibiotic molecules of diverse chemical nature. Biological activity curves of the released antibiotic were determined for both bacterial strains, which allowed to calculate the active doses that are effective against bacterial biofilms. Furthermore, in vitro biocompatibility assays on osteoblast-like cells were carried out at different periods of times. Albeit a slight decrease in cell viability was observed at the very initial stage, due to the initial burst antibiotic release, the biocompatibility of these nanosystems is evidenced since a recovery of cell viability was achieved after 72 h of assay. Biological activity curves for GM released from MSNs exhibited sustained patterns and antibiotic doses in the 2-6 μg/mL range up to 100 h, which were not enough to eradicate biofilm. In the case of LVX and RIF first-order kinetics featuring an initial burst effect followed by a sustained release above the MIC up to 96 h were observed. Such doses reduced by 99.9% bacterial biofilm and remained active up to 72 h with no emergence of bacterial resistance. This pioneering research opens up promising expectations in the design of personalized MSNs-based nanotherapies to treat chronic bone infection.

Space-Selective Chemodynamic Therapy of CuFe5O8 Nanocubes for Implant-Related Infections

Implant-related infections (IRIs) are a serious complication after orthopedic surgery, especially when a biofilm develops and establishes physical and chemical barriers protecting bacteria from antibiotics and the hosts local immune system. Effectively eliminating biofilms is essential but difficult, as it requires not only breaking the physical barrier but also changing the chemical barrier that induces an immunosuppressive microenvironment. Herein, tailored to a biofilm microenvironment (BME), we proposed a space-selective chemodynamic therapy (CDT) strategy to combat IRIs using metastable CuFe₅O₈ nanocubes (NCs) as smart Fenton-like reaction catalysts whose activity can be regulated by pH and H₂O₂ concentration. In the biofilm, extracellular DNA (eDNA) was cleaved by high levels of hydroxyl radicals (•OH) catalyzed by CuFe₅O₈ NCs, thereby disrupting the rigid biofilm. Outside the biofilm with relatively higher pH and lower H₂O₂ concentration, lower levels of generated •OH effectively reversed the immunosuppressive microenvironment by inducing pro-inflammatory macrophage polarization. Biofilm fragments and exposed bacteria were then persistently eliminated through the collaboration of pro-inflammatory immunity and •OH. The spatially selective activation of CDT and synergistic immunomodulation exerted excellent effects on the treatment of IRIs in vitro and in vivo. The anti-infection strategy is expected to provide a method to conquer IRIs.