Elaboration on the architecture of pH-sensitive surface charge-adaptive micelles with enhanced penetration and bactericidal activity in biofilms

Strategies to Promote the Journey of Nanoparticles Against Biofilm-Associated Infections

Biofilm-associated infections are one of the most challenging healthcare threats for humans, accounting for 80% of bacterial infections, leading to persistent and chronic infections. The conventional antibiotics still face their dilemma of poor therapeutic effects due to the high tolerance and resistance led by bacterial biofilm barriers. Nanotechnology-based antimicrobials, nanoparticles (NPs), are paid attention extensively and considered as promising alternative. This review focuses on the whole journey of NPs against biofilm-associated infections, and to clarify it clearly, the journey is divided into four processes in sequence as 1) Targeting biofilms, 2) Penetrating biofilm barrier, 3) Attaching to bacterial cells, and 4) Translocating through bacterial cell envelope. Through outlining the compositions and properties of biofilms and bacteria cells, recent advances and present the strategies of each process are comprehensively discussed to combat biofilm-associated infections, as well as the combined strategies against these infections with drug resistance, aiming to guide the rational design and facilitate wide application of NPs in biofilm-associated infections.

Current developments and prospects of the antibiotic delivery systems

Antibiotics have remained the cornerstone for the treatment of bacterial infections ever since their discovery in the twentieth century. The uproar over antibiotic resistance among bacteria arising from genome plasticity and biofilm development has rendered current antibiotic therapies ineffective, urging the development of innovative therapeutic approaches. The development of antibiotic resistance among bacteria has further heightened the clinical failure of antibiotic therapy, which is often linked to its low bioavailability, side effects, and poor penetration and accumulation at the site of infection. In this review, we highlight the potential use of siderophores, antibodies, cell-penetrating peptides, antimicrobial peptides, bacteriophages, and nanoparticles to smuggle antibiotics across impermeable biological membranes to achieve therapeutically relevant concentrations of antibiotics and combat antimicrobial resistance (AMR). We will discuss the general mechanisms via which each delivery system functions and how it can be tailored to deliver antibiotics against the paradigm of mechanisms underlying antibiotic resistance.

Enhancement of antimicrobial and antibiofilm activities of liposomal fatty acids

Microbial biofilms are protected surface-attached communities of bacteria or fungi with high drug tolerance that typically cause persistent infections. Smart drug carriers are being explored as a promising platform of antimicrobials to address their recalcitrance to antibiotic agents and minimize the side effects of current therapies. In this study, soy lecithin liposomes loaded with lauric acid (LA) and myristoleic acid (MA) were formulated using an emulsification method, and their antibiofilm properties were evaluated. The physio-chemical properties of the most potent liposome were characterized using a zeta sizer, transmission electron microscopy (TEM), fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. TEM and zeta sizer analysis of the liposome revealed a homogeneous spherical structure with an average size of 159.2 nm and zeta potential of - 5.4 mV. The unilamellar liposomes loaded with LA at 0.1-0.5 µg/mL achieved obvious antibiofilm efficiency against Staphylococcus aureus and Candida albicans and their dual biofilms. Also, LA-loaded liposome formulation efficiently disrupted preformed biofilms of S. aureus and C. albicans. Furthermore, formulated liposomal LA (0.1 µg/mL) exhibited 100-fold increased dual biofilm inhibition compared to LA alone. The single biofilms and dual biofilm formation on polystyrene were reduced as determined by 3D-bright field and scanning electron microscopy. Zeta potential measurements exhibited neutralized surface charge of S. aureus, and the liposomes inhibited hyphae formation in C. albicans. These findings demonstrated that the LA-incorporated liposomes have great potential to become a new, effective, and good antibiofilm agent for treating S. aureus and C. albicans infections.

Surface-charge-switch triggered self assembly of vancomycin modified carbon nanodots for enhanced photothermal eradication of vancomycin-resistant Enterococci biofilms

A new type of vancomycin (Van)-modified carbon nanodots (CNDs@Van) with pH-responsive surface charge switchable activity was successfully developed by covalently cross-linking Van on the surface of carbon nanodots (CNDs). Polymeric Van was formed on the surface of CNDs by covalent modification, which enhanced the targeted binding of CNDs@Van to vancomycin-resistant enterococci (VRE) biofilms and effectively reduced the carboxyl groups on the surface of CNDs to achieve pH-responsive surface charge switching. Most importantly, CNDs@Van was free at pH 7.4, but assembled at pH 5.5 owing to surface charge switching from negative to zero, resulting in remarkably enhanced near-infrared (NIR) absorption and photothermal properties. CNDs@Van exhibited good biocompatibility, low cytotoxicity, and weak hemolytic effects under physiological conditions (pH 7.4). Regarding targeted binding to VRE bacteria, CNDs@Van self-assembled in a weakly acidic environment (pH 5.5) generated by VRE biofilms, giving enhanced photokilling effects in in vitro and in vivo assays. Therefore, potentially, CNDs@Van can be used as a novel antimicrobial agent against VRE bacterial infections and their biofilms.

Recent progress and applications of poly(beta amino esters)-based biomaterials

Poly(beta-amino esters, PBAEs) are a promising class of cationic polymers synthesized from diacrylates and amines via Michael addition. Recently, PBAEs have been widely developed for drug delivery, immunotherapy, gene therapy, antibacterial, tissue engineering and other applications due to their convenient synthesis, good bio-compatibility and degradation properties. Herein, we mainly summarize the recent progress in the PBAEs synthesis and their applications. The amine groups of PBAEs could be protonated in low pH environment, exhibiting proton sponge and pH-sensitive abilities. Furthermore, the positive PBAEs can interact with negative genes via electrostatic interactions for efficient delivery of nucleic acids. Moreover, positive PBAEs could also directly kill bacteria by disrupting their membranes at high doses. Finally, PBAEs can augment the immune responses, and improve the bioactivity of hydrogels in tissue engineering.

Smart Bacteria-Responsive Drug Delivery Systems in Medical Implants

With the rapid development of implantable biomaterials, the rising risk of bacterial infections has drawn widespread concern. Due to the high recurrence rate of bacterial infections and the issue of antibiotic resistance, the common treatments of peri-implant infections cannot meet the demand. In this context, stimuli-responsive biomaterials have attracted attention because of their great potential to spontaneously modulate the drug releasing rate. Numerous smart bacteria-responsive drug delivery systems (DDSs) have, therefore, been designed to temporally and spatially release antibacterial agents from the implants in an autonomous manner at the infected sites. In this review, we summarized recent advances in bacteria-responsive DDSs used for combating bacterial infections, mainly according to the different trigger modes, including physical stimuli-responsive, virulence-factor-responsive, host-immune-response responsive and their combinations. It is believed that the smart bacteria-responsive DDSs will become the next generation of mainstream antibacterial therapies.

PLGA-Based Nanoplatforms in Drug Delivery for Inhibition and Destruction of Microbial Biofilm

The biofilm community of microorganisms has been identified as the dominant mode of microbial growth in nature and a common characteristic of different microorganisms such as Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. The biofilm structure helps in the protection from environmental threats including host immune system and antimicrobial agents. Thus, the biofilm community has led to a higher prevalence of multidrug-resistant (MDR) strains in recent years. In this regard, the use of a new class of antibiotics, natural compounds, and anti-biofilm enzymes has been considered for the destruction of the microbial biofilm. However, different drawbacks such as low penetration, high susceptibility to degradation, instability, and poor solubility in aqueous solutions limit the use of anti-biofilm agents (ABAs) in a clinical setting. As such, recent studies have been using poly lactic-co-glycolic acid (PLGA)-based nanoplatforms (PLGA NPFs) for delivery of ABAs that have reported promising results. These particles, due to proper drug loading and release kinetics, could suppress microbial attachment, colonization, and biofilm formation for a long time. Additionally, PLGA NPFs, because of the high drug-loading efficiencies, hydrophilic surface, negative charge, and electrostatic interaction, lead to effective penetration of antibiotics to the deeper layer of the biofilm, thereby eliminating the microbial biofilm. Thus, PLGA NPFs could be considered as a potential candidate for coating catheters and other medical material surfaces for inhibition and destruction of the microbial biofilm. However, the exact interaction of PLGA NPFs and the microbial biofilm should be evaluated in animal studies. Additionally, a future goal will be to develop PLGA formulations as systems that can be used for the treatment of the MDR microbial biofilm, since the exact interactions of PLGA NPFs and these biofilm structures are not elucidated. In the present review article, we have discussed various aspects of PLGA usage for inhibition and destruction of the microbial biofilm along with different methods and procedures that have been used for improving PLGA NPF efficacy against the microbial biofilm.

Emerging nanotechnologies for targeting antimicrobial resistance

Antimicrobial resistance is a leading cause of mortality worldwide. Without newly approved antibiotics and antifungals being brought to the market, resistance is being developed to the ones currently available to clinicians. The reason is the applied evolutionary pressure to bacterial and fungal species due to the wide overuse of common antibiotics and antifungals in clinical practice and agriculture. Biofilms harbour antimicrobial-resistant subpopulations, which make their antimicrobial treatment even more challenging. Nanoparticle-based technologies have recently been shown to successfully overcome antimicrobial resistance in both planktonic and biofilms phenotypes. This results from the combination of novel nanomaterial research and classic antimicrobial therapies which promise to deliver a whole new generation of high-performance active nanocarrier systems. This review discusses the latest developments of promising nanotechnologies with applications against resistant pathogens and evaluates their potential and feasibility for use in novel antimicrobial therapies.

Surface-Charge-Switchable and Size-Transformable Thermosensitive Nanocomposites for Chemo-Photothermal Eradication of Bacterial Biofilms in Vitro and in Vivo

The appearance of multidrug-resistant bacteria and their biofilms presents a serious threat to modern medical systems. Herein, we fabricated a novel gold-nanorod-based chemo-photothermal-integrated antimicrobial platform with surface-charge-switchable and near-infrared (NIR)-induced size-transformable activities that show an enhanced killing efficiency against methicillin-resistant Staphylococcus aureus (MRSA) in both planktonic and biofilm phenotypes. The nanocomposites are prepared by in situ copolymerization using N-isopropyl acrylamide (NIPAM), acrylic acid (AA), and N-allylmethylamine (MAA) as monomers on the surfaces of gold nanorods (GNRs). Ciprofloxacin (CIP) is loaded onto polymer shells of nanocomposites with a loading content of 9.8%. The negatively charged nanocomposites switch to positive upon passive accumulation at the infectious sites, which promotes deep biofilm penetration and bacterial adhesion of the nanoparticles. Subsequently, NIR irradiation triggers the nanocomposites to rapidly shrink in volume, further increasing the depth of biofilm penetration. The NIR-triggered, ultrafast volume shrinkage causes an instant release of CIP on the bacterial surface, realizing the synergistic benefits of chemo-photothermal therapy. Both in vitro and in vivo evidence demonstrate that drug-loaded nanocomposites could eradicate clinical MRSA biofilms. Taken together, the multifunctional chemo-photothermal-integrated antimicrobial platform, as designed, is a promising antimicrobial agent against MRSA infections.

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...

E7-Targeted Nanotherapeutics for Key HPV Afflicted Cervical Lesions by Employing CRISPR/Cas9 and Poly (Beta-Amino Ester)

Introduction

Persistent HR-HPV (high-risk human papillomavirus) infection is the main cause of cervical cancer. The HPV oncogene E7 plays a key role in HPV tumorigenesis. At present, HPV preventive vaccines are not effective for patients who already have a cervical disease, and implementation of the recommended regular cervical screening is difficult in countries and regions lacking medical resources. Therefore, patients need medications to treat existing HPV infections and thus block the progression of cervical disease.

Methods

In this study, we developed nanoparticles (NPs) composed of the non-viral vector PBAE546 and a CRISPR/Cas9 recombinant plasmid targeting HPV16 E7 as a vaginal treatment for HPV infection and related cervical malignancies.

Results

Our NPs showed low toxicity and high biological safety both in vitro (cell line viability) and in vivo (various important organs of mice). Our NPs significantly inhibited the growth of xenograft tumors derived from cervical cancer cell lines in nude mice and significantly reversed the cervical epithelial malignant phenotype of HPV16 transgenic mice.

Conclusion

Our NPs have great potential to be developed as a drug for the treatment of HPV-related cervical cancer and precancerous lesions.

Direct Surface Modification of Polycaprolactone-Based Shape Memory Materials to Introduce Positive Charge Aiming to Enhance Cell Affinity

In this study, the introduction of a positive charge on the surface of a shape memory material was investigated to enhance cell affinity. To achieve this, the direct chemical modification of a material surface was proposed. Sheet-type, crosslinked poly(caprolactone-co-α-bromo-ɤ-butyrolactone) (poly(CL-co-BrBL)) were prepared, and the direct reaction of amino compounds with bromo groups was conducted on the material surface with a positive charge. Branched poly(CL-co-BrBL) was prepared, followed by the introduction of methacryloyl groups to each chain end. Using the branched macromonomers, stable and sheet-type materials were derived through UV-light irradiation. Then, the materials were soaked in an amino compound solution to react with the bromo groups under various conditions. Differential scanning calorimetry and surface analysis of the modified materials indicated that 10 vol% of N, N-dimethylethylenediamine in n-hexane and 1 h soaking time were optimal to maintain the inherent thermal properties. The achievement of increased luminance and a positive zeta potential proved that the direct modification method effectively introduced the positive charge only on the surface, thereby enhancing cell affinity.