Dual-reactive nanogels for orthogonal functionalization of hydrophilic shell and amphiphilic network

Dual-reactive single-chain polymer nanoparticles for orthogonal functionalization through active ester and click chemistry

Glucose has been extensively studied as a targeting ligand on nanoparticles for biomedical nanoparticles. A promising nanocarrier platform are single-chain polymer nanoparticles (SCNPs). SCNPs are well-defined 5-20 nm semi-flexible nano-objects, formed by intramolecularly crosslinked linear polymers. Functionality can be incorporated by introducing labile pentafluorophenyl (PFP) esters in the polymer backbone, which can be readily substituted by functional amine-ligands. However, not all ligands are compatible with PFP-chemistry, requiring different ligation strategies for increasing versatility of surface functionalization. Here, we combine active PFP-ester chemistry with copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) click chemistry to yield dual-reactive SCNPs. First, the SCNPs are functionalized with increasing amounts of 1-amino-3-butyne groups through PFP-chemistry, leading to a range of butyne-SCNPs with increasing terminal alkyne-density. Subsequently, 3-azido-propylglucose is conjugated through the glucose C1- or C6-position by CuAAC click chemistry, yielding two sets of glyco-SCNPs. Cellular uptake is evaluated in HeLa cancer cells, revealing increased uptake upon higher glucose-surface density, with no apparent positional dependance. The general conjugation strategy proposed here can be readily extended to incorporate a wide variety of functional molecules to create vast libraries of multifunctional SCNPs.

Optically monitoring the microenvironment of a hydrophobic cargo in amphiphilic nanogels: influence of network composition on loading and release

Amphiphilic nanogels (ANGs) are promising carriers for hydrophobic cargos such as drugs, dyes, and catalysts. Loading content and release kinetics of these compounds are controlled by type and number of hydrophobic groups in the amphiphilic copolymer network. Thus, understanding the interactions between cargo and colloidal carrier is mandatory for a tailor-made and cargo-specific ANG design. To systematically explore the influence of the network composition on these interactions, we prepared a set of ANGs of different amphiphilicity and loaded these ANGs with varying concentrations of the solvatochromic dye Nile Red (NR). Here, NR acts as a hydrophobic model cargo to optically probe the polarity of its microenvironment. Analysis of the NR emission spectra as well as measurements of the fluorescence quantum yields and decay kinetics revealed a decrease in the polarity of the NR microenvironment with increasing hydrophobicity of the hydrophobic groups in the ANG network and dye-dye interactions at higher loading concentrations. At low NR concentrations, the hydrophobic cargo NR is encapsulated in the hydrophobic domains. Increasing NR concentrations resulted in probe molecules located in a more hydrophilic environment, i.e., at the nanodomain border, and favored dye-dye interactions and NR aggregation. These results correlate well with release experiments, indicating first NR release from more hydrophilic network locations. Overall, our findings demonstrate the importance to understand carrier-drug interactions for efficient loading and controlled release profiles in amphiphilic nanogels.

Rational Design and Development of Polymeric Nanogels as Protein Carriers

Proteins have gained significant attention as potential therapeutic agents owing to their high specificity and reduced toxicity. Nevertheless, their clinical utility is hindered by inherent challenges associated with stability during storage and after in vivo administration. To overcome these limitations, polymeric nanogels (NGs) have emerged as promising carriers. These colloidal systems are capable of efficient encapsulation and stabilization of protein cargoes while improving their bioavailability and targeted delivery. The design of such delivery systems requires a comprehensive understanding of how the synthesis and formulation processes affect the final performance of the protein. This review highlights critical aspects involved in the development of NGs for protein delivery, with specific emphasis on loading strategies and evaluation techniques. For example, factors influencing loading efficiency and release kinetics are discussed, along with strategies to optimize protein encapsulation through protein-carrier interactions to achieve the desired therapeutic outcomes. The discussion is based on recent literature examples and aims to provide valuable insights for researchers working toward the advancement of protein-based therapeutics.

Recent Advances in the Biomedical Applications of Functionalized Nanogels

Nanomaterials have been extensively used in several applications in the past few decades related to biomedicine and healthcare. Among them, nanogels (NGs) have emerged as an important nanoplatform with the properties of both hydrogels and nanoparticles for the controlled/sustained delivery of chemo drugs, nucleic acids, or other bioactive molecules for therapeutic or diagnostic purposes. In the recent past, significant research efforts have been invested in synthesizing NGs through various synthetic methodologies such as free radical polymerization, reversible addition-fragmentation chain-transfer method (RAFT) and atom transfer radical polymerization (ATRP), as well as emulsion techniques. With further polymeric functionalizations using activated esters, thiol-ene/yne processes, imines/oximes formation, cycloadditions, nucleophilic addition reactions of isocyanates, ring-opening, and multicomponent reactions were used to obtain functionalized NGs for targeted delivery of drug and other compounds. NGs are particularly intriguing for use in the areas of diagnosis, analytics, and biomedicine due to their nanodimensionality, material characteristics, physiological stability, tunable multi-functionality, and biocompatibility. Numerous NGs with a wide range of functionalities and various external/internal stimuli-responsive modalities have been possible with novel synthetic reliable methodologies. Such continuous development of innovative, intelligent materials with novel characteristics is crucial for nanomedicine for next-generation biomedical applications. This paper reviews the synthesis and various functionalization strategies of NGs with a focus on the recent advances in different biomedical applications of these surface modified/functionalized single-/dual-/multi-responsive NGs, with various active targeting moieties, in the fields of cancer theranostics, immunotherapy, antimicrobial/antiviral, antigen presentation for the vaccine, sensing, wound healing, thrombolysis, tissue engineering, and regenerative medicine.