Antimicrobial Photodynamic Therapy Involving a Novel Photosensitizer Combined With an Antibiotic in the Treatment of Rabbit Tibial Osteomyelitis Caused by Drug-Resistant Bacteria

Nanobioactive glass/chitosan/collagen composite loaded with methylene blue for tissue regeneration and bacterial infection treatment by photodynamic therapy

Development of suitable tissue engineering scaffolds to be loaded with photosensitizer drugs applied in photodynamic therapy is considered a critical issue. This study we introduced new delivery system based on cerium- and silver-doped nanobioactive glass (nBG)/chitosan/collagen composite scaffolds as a carrier for a photosensitizer, methylene blue (MB), in photodynamic therapy, capitalizing on the unique photocatalytic and antibacterial properties of the doped nBG. Cerium and silver offer additional benefits in terms of antimicrobial, anticancer, and wound healing properties. MB is an effective and inexpensive therapeutic photosensitizer compound that exhibits antimicrobial activity through light activation and has shown great potential for selectively treating infected cells. The prepared scaffolds were characterized by FTIR, TGA, and SEM/EDX. The bioactivity and biodegradation were conducted in SBF. The cell viability was carried out against the WI-38 cell line. Finally, the antibacterial efficiency of scaffolds loaded with MB was evaluated before and after laser irradiation against Staphylococcus aureus, Bacillus subtilis (Gram-Positive), and Pseudomonas aerginousea, klebsiella pneumoniae (Gram-negative). Inhibition of bacteria by reactive oxygen species (ROS) was also measured. Furthermore the primarily MB release profile and kinetic were studied. The results showed that nBG particles increased the thermal stability of the scaffolds, and enhanced the formation of an apatite bone-like layer on the scaffold surfaces. Furthermore, scaffold degradation was tailored by changing the amount of nBG. Moreover, the water uptake of the scaffold containing undoped nBG particles (G010 and G020 samples) showed higher water uptake percentages (682 % and 762 %, respectively) than doped nBG (for 155 % and 322 % for GA10 and GA20, respectively). All scaffolds demonstrated good cell viability at concentrations up to 62.5 μg/ml. However, at higher concentrations, scaffolds incorporating high percentages of nBG were more viable than those containing low amounts of nBG, regardless of the glass composition. The antibacterial tests presented that the MB enhanced scaffold antibacterial efficiency by improving the oxidative stress on bacterial cells, which significantly increased after irradiation. Finally, the release mechanism of MB was diffusion mechanism for scaffolds contained nBG particles, while it did not follow this mechanism for blank polymer scaffolds. In conclusion, these results suggest that the developed multifunctional scaffolds hold significant promise for effective photodynamic antimicrobial chemotherapy in the treatment of microbial infections.

A comprehensive review of pathology and treatment of staphylococcus aureus osteomyelitis

Osteomyelitis (OM) is an inflammation of the bone and bone marrow triggered by infectious pathogens which may induce progressive bone destruction. The majority of OM cases, especially the chronic OM cases, are induced by the most prevalent and devastating pathogen Staphylococcus aureus (S. aureus), partially due to its resistance mechanisms against the immune system and antibiotic therapies. Regarding the high rate of morbidity and recurrence in patients, it is pivotal to elucidate underlying mechanisms that how S. aureus enter and survive in hosts. The accumulated discoveries have identified multiple distinct strategies associated with chronicity and recurrence include biofilm development, small colony variants (SCVs), staphylococcus abscess communities (SACs), the osteocyte lacuno-canalicular network invasion (OLCN) of cortical bones, and S. aureus protein A (SpA). Unfortunately, little clinical progress has been achieved for the diagnosis and therapeutic treatment for OM patients, indicating that numerous questions remain to be solved. Therefore, we still have a long way to obtain the clear elucidation of the host-pathogen interactions which could be applied for clinical treatment of OM. In this review, we provide insights of current knowledge about how S. aureus evades immune eradication and remains persistent in hosts with recent discoveries. The common and novel treatment strategies for OM are also described. The purpose of this review is to have in-dept understanding of S. aureus OM and bring new perspectives to therapeutic fields which may be translated to the clinic.

Antimicrobial photodynamic therapy with 5-aminolevulinic acid plus antibiotics: a promising treatment for tibial osteomyelitis caused by drug-resistant bacteria

Osteomyelitis is a severely destructive bone disease caused by microbial infections, and currently, no available treatment effectively controls the infection. 5-Aminolevulinic acid is a second-generation endogenous photosensitizer. This study investigated the efficacy of 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) in combination with antibiotics in the treatment of tibial osteomyelitis in rabbits. The results illustrated that ALA-PDT alone and in combination of antibiotics displayed significant efficacy in treating osteomyelitis. Animals in the photodynamic antimicrobial chemotherapy (PACT) + antibiotics group exhibited a higher survival rate, an improved overall mental status, a lower localized infection rate, and reduced Tang Hui and Norden scores (P < 0.05), indicating less severe bone destruction. Histologically, more strips of lamellar new bone formation and more pronounced periosteal hyperplasia were noted in the PACT + antibiotics group. Micro-computed tomography illustrated that the structural integrity of cortical bone and cancellous bone structure had better continuity and clearer display in the PACT + antibiotics group than in the other groups, and the periosteal reaction in the modeling area was the most obvious. Bone parameter analysis indicated that trabecular thickness, bone volume, and trabeculae volume were significantly higher in the PACT + antibiotics group than in the model and antibiotics groups (P < 0.05). Additionally, trabecular separation was significantly lower in the PACT + antibiotic group than in the other groups (P < 0.05). These findings suggest that the combination of ALA-PDT and antibiotics has a sensitizing therapeutic effect, offering a promising strategy for the clinical treatment of osteomyelitis.

Exploring the efficacy of photodynamic antimicrobial chemotherapy on diabetic foot ulcers in rats

We investigate the efficacy of photodynamic antimicrobial chemotherapy (PACT) and its combination with an antibiotic in the treatment of diabetic foot ulcers (DFUs) in rats using a novel cationic amino acid porphyrin-based photosensitizer. The research findings demonstrate that the combination of novel cationic photosensitizer-mediated PACT and an antibiotic exhibits significant therapeutic efficacy in treating deep ulcers in a rat model of DFUs. Moreover, the PACT + Antibiotic group displays enhanced angiogenesis, improved tissue maturation, and superior wound healing effect. Micro-computed tomography examination showed that the periosteal reaction was most obvious in the PACT + Antibiotic group. The cortical bone volume ratio (BV/TV), the bone mineral density, and trabecular thickness were significantly higher in the PACT + Antibiotic group than in the model group (p < 0.05). The combination of PACT and antibiotic plays a sensitizing therapeutic role, which provides a new idea for the clinical treatment of DFUs.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

Injectable Nano-Micro Composites with Anti-bacterial and Osteogenic Capabilities for Minimally Invasive Treatment of Osteomyelitis

The effective management of osteomyelitis remains extremely challenging due to the difficulty associated with treating bone defects, the high probability of recurrence, the requirement of secondary surgery or multiple surgeries, and the difficulty in eradicating infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Hence, smart biodegradable biomaterials that provide effective and precise local anti-infection effects and can promote the repair of bone defects are actively being developed. Here, a novel nano-micro composite is fabricated by combining calcium phosphate (CaP) nanosheets with drug-loaded GelMA microspheres via microfluidic technology. The microspheres are covalently linked with vancomycin (Van) through an oligonucleotide (oligo) linker using an EDC/NHS carboxyl activator. Accordingly, a smart nano-micro composite called "CaP@MS-Oligo-Van" is synthesized. The porous CaP@MS-Oligo-Van composites can target and capture bacteria. They can also release Van in response to the presence of bacterial micrococcal nuclease and Ca2+, exerting additional antibacterial effects and inhibiting the inflammatory response. Finally, the released CaP nanosheets can promote bone tissue repair. Overall, the findings show that a rapid, targeted drug release system based on CaP@MS-Oligo-Van can effectively target bone tissue infections. Hence, this agent holds potential in the clinical treatment of osteomyelitis caused by MRSA.

Establishment of a mandible defect model in rabbits infected with multiple bacteria and bioinformatics analysis

Objective: A model of chronic infectious mandibular defect (IMD) caused by mixed infection with Staphylococcus aureus and Pseudomonas aeruginosa was established to explore the occurrence and development of IMD and identify key genes by transcriptome sequencing and bioinformatics analysis. Methods: S. aureus and P. aeruginosa were diluted to 3 × 108 CFU/mL, and 6 × 3 × 3 mm defects lateral to the Mandibular Symphysis were induced in 28 New Zealand rabbits. Sodium Morrhuate (0.5%) and 50 μL bacterial solution were injected in turn. The modeling was completed after the bone wax closed; the effects were evaluated through postoperative observations, imaging and histological analyses. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein‒protein interaction (PPI) network analyses were performed to investigate the function of the differentially expressed genes (DEGs). Results: All rabbits showed characteristics of infection. The bacterial cultures were positive, and polymerase chain reaction (PCR) was used to identify S. aureus and P. aeruginosa. Cone beam CT and histological analyses showed inflammatory cell infiltration, pus formation in the medullary cavity, increased osteoclast activity in the defect area, and blurring at the edge of the bone defect. Bioinformatics analysis showed 1,804 DEGs, 743 were upregulated and 1,061 were downregulated. GO and KEGG analyses showed that the DEGs were enriched in immunity and osteogenesis inhibition, and the core genes identified by the PPI network were enriched in the Hedgehog pathway, which plays a role in inflammation and tissue repair; the MEF2 transcription factor family was predicted by IRegulon. Conclusion: By direct injection of bacterial solution into the rabbit mandible defect area, the rabbit chronic IMD model was successfully established. Based on the bioinformatics analysis, we speculate that the Hedgehog pathway and the MEF2 transcription factor family may be potential intervention targets for repairing IMD.

Synthesis and photodynamic antimicrobial chemotherapy against multi-drug resistant Proteus mirabilis of ornithine-porphyrin conjugates in vitro and in vivo

For the treatment of bacterial infections, photodynamic antimicrobial chemotherapy (PACT) has the advantage of circumventing multi-drug resistance. In this work, new cationic photosensitizers against multi-drug resistant Proteus mirabilis (MRPM) were designed and synthesized by the conjugation of amino phenyl porphyrin with basic amino acid L-ornithine. Their photoinactivation efficacies against MRPM in vitro were reported and include the influence of laser energy, uptake, MIC and MBC, dose-dependent photoinactivation effects, membrane integrity, and fluorescence imaging. The PACT in vivo was evaluated using a wound mouse model infected by MRPM. Photosensitizer 4d displayed high photo inactivation efficacy against MRPM at 7.81 μM under illumination, and it could accelerate wound healing via bactericidal effect. These ornithine-porphyrin conjugates are potential photosensitizers for PACT in the treatment of MRPM infection.