Influence of nanostructure morphology on host capacity and kinetics of guest release

Engineering a nanoantibiotic system displaying dual mechanism of action

In recent decades, peptide amphiphiles (PAs) have established themselves as promising self-assembling bioinspired materials in a wide range of medical fields. Herein, we report a dual-therapeutic system constituted by an antimicrobial PA and a cylindrical protease inhibitor (LJC) to achieve broad antimicrobial spectrum and to enhance therapeutic efficacy. We studied two strategies: PA-LJC nanostructures (Encapsulation) and PA nanostructures + free LJC (Combination). Computational modeling using a molecular theory for amphiphile self-assembly captures and explains the morphology of PA-LJC nanostructures and the location of encapsulated LJC in agreement with transmission electron microscopy and two-dimensional (2D) NMR observations. The morphology and release profile of PA-LJC assemblies are strongly correlated to the PA:LJC ratio: high LJC loading induces an initial burst release. We then evaluated the antimicrobial activity of our nanosystems toward gram-positive and gram-negative bacteria. We found that the Combination broadens the spectrum of LJC, reduces the therapeutic concentrations of both agents, and is not impacted by the inoculum effect. Further, the Encapsulation provides additional benefits including bypassing water solubility limitations of LJC and modulating the release of this molecule. The different properties of PA-LJC nanostructures results in different killing profiles, and reduced cytotoxicity and hemolytic activity. Meanwhile, details in membrane alterations caused by each strategy were revealed by various microscopy and fluorescent techniques. Last, in vivo studies in larvae treated by the Encapsulation strategy showed better antimicrobial efficacy than polymyxin B. Collectively, this study established a multifunctional platform using a versatile PA to act as an antibiotic, membrane-penetrating assistant, and slow-release delivery vehicle.

“Breathing” unimolecular micelles based on a novel star-like amphiphilic hybrid copolymer

Novel unimolecular micelles that possess a pH-induced “breathing” feature are presented in this paper.

Shell crosslinked knedel-like nanoparticles for delivery of cisplatin: effects of crosslinking

Polymeric micelles and shell crosslinked knedel-like (SCK) nanoparticles were loaded with up to 48% (w/w) cisplatin. These spherical cisplatin-loaded nanoparticles displayed sustained platinum release over 5 days in PBS, enhanced stability over free cisplatin in aqueous milieu, and significant antitumor activity in vitro against two cancer cell lines.

Hierarchically assembled theranostic nanostructures for siRNA delivery and imaging applications

Dual functional hierarchically assembled nanostructures, with two unique functions of carrying therapeutic cargo electrostatically and maintaining radiolabeled imaging agents covalently within separate component building blocks, have been developed via the supramolecular assembly of several spherical cationic shell cross-linked nanoparticles clustered around a central anionic shell cross-linked cylinder. The shells of the cationic nanoparticles and the hydrophobic core domain of the anionic central cylindrical nanostructure of the assemblies were utilized to complex negatively charged nucleic acids (siRNA) and to undergo radiolabeling, respectively, for potential theranostic applications. The assemblies exhibited exceptional cell transfection and radiolabeling efficiencies, providing an overall advantage over the individual components, which could each facilitate only one or the other of the functions.

Endothelial targeting of polymeric nanoparticles stably labeled with the PET imaging radioisotope iodine-124

Targeting of therapeutics or imaging agents to the endothelium has the potential to improve specificity and effectiveness of treatment for many diseases. One strategy to achieve this goal is the use of nanoparticles (NPs) targeted to the endothelium by ligands of protein determinants present on this tissue, including cell adhesion molecules, peptidases, and cell receptors. However, detachment of the radiolabel probes from NPs poses a significant problem. In this study, we devised polymeric NPs directly labeled with radioiodine isotopes including the positron emission tomography (PET) isotope (124)I, and characterized their targeting to specific endothelial determinants. This approach provided sizable, targetable probes for specific detection of endothelial surface determinants non-invasively in live animals. Direct conjugation of radiolabel to NPs allowed for stable longitudinal tracking of tissue distribution without label detachment even in an aggressive proteolytic environment. Further, this approach permits tracking of NP pharmacokinetics in real-time and non-invasive imaging of the lung in mice using micro-PET imaging. The use of this strategy will considerably improve investigation of NP interactions with target cells and PET imaging in small animals, which ultimately can aid in the optimization of targeted drug delivery.

Biological stimuli and biomolecules in the assembly and manipulation of nanoscale polymeric particles

Living systems are replete with complex, stimuli-responsive nanoscale materials and molecular self-assemblies. There is an ever increasing and intense interest within the chemical sciences to understand, mimic and interface with these biological systems utilizing synthetic and/or semi-synthetic tools. Our aim in this review is to give perspective on this emerging field of research by highlighting examples of polymeric nanoparticles and micelles that are prepared utilizing biopolymers together with synthetic polymers for the purpose of developing nanomaterials capable of interacting and responding to biologically relevant stimuli. It is expected that with the merging of evolved biological molecules with synthetic materials, will come the ability to prepare complex, functional devices. A variety of applications will become accessible including self-healing materials, self-replicating systems, biodiagnostic tools, drug targeting materials and autonomous, adaptive sensors. Most importantly, the success of this type of strategy will impact how biomolecules are stabilized and incorporated into synthetic devices and at the same time, will influence how synthetic materials are utilized within biomedical applications.

Design of polymeric nanoparticles for biomedical delivery applications

Polymeric nanoparticles-based therapeutics show great promise in the treatment of a wide range of diseases, due to the flexibility in which their structures can be modified, with intricate definition over their compositions, structures and properties. Advances in polymerization chemistries and the application of reactive, efficient and orthogonal chemical modification reactions have enabled the engineering of multifunctional polymeric nanoparticles with precise control over the architectures of the individual polymer components, to direct their assembly and subsequent transformations into nanoparticles of selective overall shapes, sizes, internal morphologies, external surface charges and functionalizations. In addition, incorporation of certain functionalities can modulate the responsiveness of these nanostructures to specific stimuli through the use of remote activation. Furthermore, they can be equipped with smart components to allow their delivery beyond certain biological barriers, such as skin, mucus, blood, extracellular matrix, cellular and subcellular organelles. This tutorial review highlights the importance of well-defined chemistries, with detailed ties to specific biological hurdles and opportunities, in the design of nanostructures for various biomedical delivery applications.

Degradability of poly(lactic acid)-containing nanoparticles: enzymatic access through a cross-linked shell barrier

Comparative studies of bulk samples of hydrolytically degradable poly(lactic acid) (PLA) vs core-shell block copolymer micelles having PLA cores revealed remarkable acceleration in the proteinase K enzymatic hydrolysis of the nanoparticulate forms and demonstrated that even with amidation-based shell cross-linking the core domain remained accessible. Kinetic analyses by (1)H NMR spectroscopy showed less than 20% lactic acid released from enzymatically catalyzed hydrolysis of poly(l-lactic acid) in bulk, whereas ca. 70% of the core degraded within 48 h for block copolymer micelles of poly(N-(acryloyloxy)succinimide-copolymer-N-acryloylmorpholine)-block-poly(L-lactic acid) (P(NAS-co-NAM)-b-PLLA), with only a slight reduction to ca. 50% for the shell cross-linked derivatives. Rigorous characterization measurements by NMR spectroscopy, fluorescence spectroscopy, dynamic light scattering, atomic force microscopy, and transmission electron microscopy were employed to confirm core excavation. These studies provide important fundamental understanding of the effects of nanoscopic dimensions on protein-polymer interactions and polymer degradability, which will guide the development of these degradable nanoconstructs to reach their potential for controlled release of therapeutics and biological clearance.