Nanoparticle biointerfacing by platelet membrane cloaking.

Development of functional nanoparticles can be encumbered by unanticipated material properties and biological events, which can affect nanoparticle effectiveness in complex, physiologically relevant systems. Despite the advances in bottom-up nanoengineering and surface chemistry, reductionist functionalization approaches remain inadequate in replicating the complex interfaces present in nature and cannot avoid exposure of foreign materials. Here we report on the preparation of polymeric nanoparticles enclosed in the plasma membrane of human platelets, which are a unique population of cellular fragments that adhere to a variety of disease-relevant substrates. The resulting nanoparticles possess a right-side-out unilamellar membrane coating functionalized with immunomodulatory and adhesion antigens associated with platelets. Compared to uncoated particles, the platelet membrane-cloaked nanoparticles have reduced cellular uptake by macrophage-like cells and lack particle-induced complement activation in autologous human plasma. The cloaked nanoparticles also display platelet-mimicking properties such as selective adhesion to damaged human and rodent vasculatures as well as enhanced binding to platelet-adhering pathogens. In an experimental rat model of coronary restenosis and a mouse model of systemic bacterial infection, docetaxel and vancomycin, respectively, show enhanced therapeutic efficacy when delivered by the platelet-mimetic nanoparticles. The multifaceted biointerfacing enabled by the platelet membrane cloaking method provides a new approach in developing functional nanoparticles for disease-targeted delivery.

In vivo treatment of Helicobacter pylori infection with liposomal linolenic acid reduces colonization and ameliorates inflammation.

Helicobacter pylori infection is marked by a vast prevalence and strong association with various gastric diseases, including gastritis, peptic ulcers, and gastric cancer. Because of the rapid emergence of H. pylori strains resistant to existing antibiotics, current treatment regimens show a rapid decline of their eradication rates. Clearly, novel antibacterial strategies against H. pylori are urgently needed. Here, we investigated the in vivo therapeutic potential of liposomal linolenic acid (LipoLLA) for the treatment of H. pylori infection. The LipoLLA formulation with a size of ∼ 100 nm was prone to fusion with bacterial membrane, thereby directly releasing a high dose of linolenic acids into the bacterial membrane. LipoLLA penetrated the mucus layer of mouse stomach, and a significant portion of the administered LipoLLA was retained in the stomach lining up to 24 h after the oral administration. In vivo tests further confirmed that LipoLLA was able to kill H. pylori and reduce bacterial load in the mouse stomach. LipoLLA treatment was also shown to reduce the levels of proinflammatory cytokines including interleukin 1ß, interleukin 6, and tumor necrosis factor alpha, which were otherwise elevated because of the H. pylori infection. Finally, a toxicity test demonstrated excellent biocompatibility of LipoLLA to normal mouse stomach. Collectively, results from this study indicate that LipoLLA is a promising, effective, and safe therapeutic agent for the treatment of H. pylori infection.

Micromotors Spontaneously Neutralize Gastric Acid for pH-Responsive Payload Release.

The highly acidic gastric environment creates a physiological barrier for using therapeutic drugs in the stomach. While proton pump inhibitors have been widely used for blocking acid-producing enzymes, this approach can cause various adverse effects. Reported herein is a new microdevice, consisting of magnesium-based micromotors which can autonomously and temporally neutralize gastric acid through efficient chemical propulsion in the gastric fluid by rapidly depleting the localized protons. Coating these micromotors with a cargo-containing pH-responsive polymer layer leads to autonomous release of the encapsulated payload upon gastric-acid neutralization by the motors. Testing in a mouse model demonstrate that these motors can safely and rapidly neutralize gastric acid and simultaneously release payload without causing noticeable acute toxicity or affecting the stomach function, and the normal stomach pH is restored within 24 h post motor administration.

Nanoparticle-stabilized liposomes for pH-responsive gastric drug delivery.

We report a novel pH-responsive gold nanoparticle-stabilized liposome system for gastric antimicrobial delivery. By adsorbing small chitosan-modified gold nanoparticles (diameter ~10 nm) onto the outer surface of negatively charged phospholipid liposomes (diameter ~75 nm), we show that at gastric pH the liposomes have excellent stability with limited fusion ability and negligible cargo releases. However, when the stabilized liposomes are present in an environment with neutral pH, the gold stabilizers detach from the liposomes, resulting in free liposomes that can actively fuse with bacterial membranes. Using Helicobacter pylori as a model bacterium and doxycycline as a model antibiotic, we demonstrate such pH-responsive fusion activity and drug release profile of the nanoparticle-stabilized liposomes. Particularly, at neutral pH the gold nanoparticles detach, and thus the doxycycline-loaded liposomes rapidly fuse with bacteria and cause superior bactericidal efficacy as compared to the free doxycycline counterpart. Our results suggest that the reported liposome system holds a substantial potential for gastric drug delivery; it remains inactive (stable) in the stomach lumen but actively interacts with bacteria once it reaches the mucus layer of the stomach where the bacteria may reside.

Antibacterial activities of liposomal linolenic acids against antibiotic-resistant Helicobacter pylori.

Helicobacter pylori (H. pylori) infection with its vast prevalence is responsible for various gastric diseases including gastritis, peptic ulcers, and gastric malignancy. While effective, current treatment regimens are challenged by a fast-declining eradication rate due to the increasing emergence of H. pylori strains resistant to existing antibiotics. Therefore, there is an urgent need to develop novel antibacterial strategies against H. pylori. In this study, we developed a liposomal nanoformulation of linolenic acid (LipoLLA) and evaluated its bactericidal activity against resistant strains of H. pylori. Using a laboratory strain of H. pylori, we found that LipoLLA was effective in killing both spiral and coccoid forms of the bacteria via disrupting bacterial membranes. Using a metronidazole-resistant strain of H. pylori and seven clinically isolated strains, we further demonstrated that LipoLLA eradicated all strains of the bacteria regardless of their antibiotic resistance status. Furthermore, under our experimental conditions, the bacteria did not develop drug resistance when cultured with LipoLLA at various sub-bactericidal concentrations, whereas they rapidly acquired resistance to both metronidazole and free linolenic acid (LLA). Our findings suggest that LipoLLA is a promising antibacterial nanotherapeutic to treat antibiotic-resistant H. pylori infection.

A Bioadhesive Nanoparticle-Hydrogel Hybrid System for Localized Antimicrobial Drug Delivery.

Effective antibacterial treatment at the infection site associated with high shear forces remains challenging, owing largely to the lack of durably adhesive and safe delivery platforms that can enable localized antibiotic accumulation against bacterial colonization. Inspired by delivery systems mimicking marine mussels for adhesion, herein, we developed a bioadhesive nanoparticle-hydrogel hybrid (NP-gel) to enhance localized antimicrobial drug delivery. Antibiotics were loaded into polymeric nanoparticles and then embedded into a 3D hydrogel network that confers adhesion to biological surfaces. The combination of two distinct delivery platforms, namely, nanoparticles and hydrogel, allows the hydrogel network properties to be independently tailored for adhesion while maintaining controlled and prolonged antibiotic release profile from the nanoparticles. The bioadhesive NP-gel developed here showed superior adhesion and antibiotic retention under high shear stress on a bacterial film, a mammalian cell monolayer, and mouse skin tissue. Under a flow environment, the NP-gel inhibited the formation of an Escherichia coli bacterial film. When applied on mouse skin tissue for 7 consecutive days, the NP-gel did not generate any observable skin reaction or toxicity, implying its potential as a safe and effective local delivery platform against microbial infections.

Mechanism of antibacterial activity of liposomal linolenic acid against Helicobacter pylori.

Helicobacter pylori infects approximately half of the world population and is a major cause of gastritis, peptic ulcer, and gastric cancer. Moreover, this bacterium has quickly developed resistance to all major antibiotics. Recently, we developed a novel liposomal linolenic acid (LipoLLA) formulation, which showed potent bactericidal activity against several clinical isolated antibiotic-resistant strains of H. pylori including both the spiral and coccoid form. In addition, LipoLLA had superior in vivo efficacy compared to the standard triple therapy. Our data showed that LipoLLA associated with H. pylori cell membrane. Therefore, in this study, we investigated the possible antibacterial mechanism of LipoLLA against H. pylori. The antibacterial activity of LipoLLA (C18:3) was compared to that of liposomal stearic acid (LipoSA, C18:0) and oleic acid (LipoOA, C18:1). LipoLLA showed the most potent bactericidal effect and completely killed H. pylori within 5 min. The permeability of the outer membrane of H. pylori increased when treated with LipoOA and LipoLLA. Moreover, by detecting released adenosine triphosphate (ATP) from bacteria, we found that bacterial plasma membrane of H. pylori treated with LipoLLA exhibited significantly higher permeability than those treated with LipoOA, resulting in bacteria cell death. Furthermore, LipoLLA caused structural changes in the bacterial membrane within 5 min affecting membrane integrity and leading to leakage of cytoplasmic contents, observed by both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Our findings showing rapid bactericidal effect of LipoLLA suggest it is a very promising new, effective anti-H. pylori agent.

Artificial micromotors in the mouse's stomach: a step toward in vivo use of synthetic motors.

Artificial micromotors, operating on locally supplied fuels and performing complex tasks, offer great potential for diverse biomedical applications, including autonomous delivery and release of therapeutic payloads and cell manipulation. Various types of synthetic motors, utilizing different propulsion mechanisms, have been fabricated to operate in biological matrices. However, the performance of these man-made motors has been tested exclusively under in vitro conditions (outside the body); their behavior and functionalities in an in vivo environment (inside the body) remain unknown. Herein, we report an in vivo study of artificial micromotors in a living organism using a mouse model. Such in vivo evaluation examines the distribution, retention, cargo delivery, and acute toxicity profile of synthetic motors in mouse stomach via oral administration. Using zinc-based micromotors as a model, we demonstrate that the acid-driven propulsion in the stomach effectively enhances the binding and retention of the motors as well as of cargo payloads on the stomach wall. The body of the motors gradually dissolves in the gastric acid, autonomously releasing their carried payloads, leaving nothing toxic behind. This work is anticipated to significantly advance the emerging field of nano/micromotors and to open the door to in vivo evaluation and clinical applications of these synthetic motors.

Hydrogel containing nanoparticle-stabilized liposomes for topical antimicrobial delivery.

Adsorbing small charged nanoparticles onto the outer surfaces of liposomes has become an effective strategy to stabilize liposomes against fusion prior to "seeing" target bacteria, yet allow them to fuse with the bacteria upon arrival at the infection sites. As a result, nanoparticle-stabilized liposomes have become an emerging drug delivery platform for treatment of various bacterial infections. To facilitate the translation of this platform for clinical tests and uses, herein we integrate nanoparticle-stabilized liposomes with hydrogel technology for more effective and sustained topical drug delivery. The hydrogel formulation not only preserves the structural integrity of the nanoparticle-stabilized liposomes, but also allows for controllable viscoeleasticity and tunable liposome release rate. Using Staphylococcus aureus bacteria as a model pathogen, we demonstrate that the hydrogel formulation can effectively release nanoparticle-stabilized liposomes to the bacterial culture, which subsequently fuse with bacterial membrane in a pH-dependent manner. When topically applied onto mouse skin, the hydrogel formulation does not generate any observable skin toxicity within a 7-day treatment. Collectively, the hydrogel containing nanoparticle-stabilized liposomes hold great promise for topical applications against various microbial infections.

In vivo treatment of Propionibacterium acnes infection with liposomal lauric acids.

Propionibacterium acnes (P. acnes) is a Gram-positive bacterium strongly associated with acne infection. While many antimicrobial agents have been used in clinic to treat acne infection by targeting P. acnes, these existing anti-acne agents usually produce considerable side effects. Herein, the development and evaluation of liposomal lauric acids (LipoLA) is reported as a new, effective and safe therapeutic agent for the treatment of acne infection. By incorporating lauric acids into the lipid bilayer of liposomes, it is observed that the resulting LipoLA readily fuse with bacterial membranes, causing effective killing of P. acnes by disrupting bacterial membrane structures. Using a mouse ear model, we demonstrated that the bactericidal property of LipoLA against P. acne is well preserved at physiological conditions. Topically applying LipoLA in a gel form onto the infectious sites leads to eradication of P. acnes bacteria in vivo. Further skin toxicity studies show that LipoLA does not induce acute toxicity to normal mouse skin, while benzoyl peroxide and salicylic acid, the two most popular over-the-counter acne medications, generate moderate to severe skin irritation within 24 h. These results suggest that LipoLA hold a high therapeutic potential for the treatment of acne infection and other P. acnes related diseases.