Polycations that absorb protons in response to the acidification of endosomes can theoretically disrupt these vesicles via the "proton sponge" effect. To exploit this mechanism, we created nanoparticles with a segregated core-shell structure for efficient, noncytotoxic intracellular drug delivery. Cross-linked polymer nanoparticles were synthesized with a pH-responsive core and hydrophilic charged shell designed to disrupt endosomes and mediate drug/cell binding, respectively. By sequestering the relatively hydrophobic pH-responsive core component within a more hydrophilic pH-insensitive shell, nontoxic delivery of small molecules and proteins to the cytosol was achieved in dendritic cells, a key cell type of interest in the context of vaccines and immunotherapy.

Novel biomaterials are beneficial to the growing fields of drug delivery, cell biology, micro-devices, and tissue engineering. With recent advances in chemistry and materials science, light is becoming an attractive option as a method to control biomaterial behavior and properties. In this Feature Article, we explore some of the early and recent advances in the design of light-responsive biomaterials. Particular attention is paid to macromolecular assemblies for drug delivery, multi-component surface patterning for advanced cell assays, and polymer networks that undergo chemical or shape changes upon light exposure. We conclude with some remarks about future directions of the field.

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Polymeric vesicles, or polymersomes, constitute a relatively new class of materials based on the self-assembly of amphiphilic block copolymers. 1 Polymersomes offer several distinct advantages over liposomes, including increased mechanical robustness, the ability to solubilize large quantities of hydrophobic and hydrophilic molecules, and typically a complete poly(ethylene glycol) (PEG) surface functionality, offering a stealth character in vivo. Polymersomes are useful in a range of applications, including drug delivery, in vivo imaging, and use as cell mimetics. [2][3][4][5][6] The majority of application-based research has focused on systems using existing diblock polymers. However, new synthetic routes that introduce additional functionality may be beneficial for other applications or increasing the polymersome efficacy. 7 We present here a novel synthetic route that utilizes modular construction of biodegradable block polymers, allowing for the incorporation of a wide variety of chemical groups in the membrane. As two examples, we developed polymersomes that are susceptible to UV-induced degradation or include fluorescence directly in the hydrophobic core of the membrane.This method for diblock synthesis was inspired by chemistry commonly used for solid-phase peptide synthesis and utilizes amino acids with any desired side groups. 8 In the first step, an FMOCprotected amino acid is conjugated to an amine-terminated PEG through an amidation reaction (Scheme 1; for complete Materials and Methods, see the Supporting Information). Following FMOC removal and purification, the functional PEG (still with an amine terminus) is coupled in excess to a carboxy-terminated poly(caprolactone) (PCL) through a second amidation reaction. Precipitation of the resulting polymer into methanol selectively precipitates the diblock copolymer, yielding the desired product.As a first example, we incorporated photolabile 2-nitrophenylalanine (2NPA) as the amino acid joining the two blocks. Incorporation of this amino acid into the backbones of polypeptides has enabled sitespecific cleavage of the peptide bond between the 2NPA and the next amino acid toward the N-terminus. 9 Initial characterization of the polymer via NMR spectroscopy confirmed the coupling of the 2NPA to PEG and subsequent coupling to the PCL ( Figure S1 in the Supporting Information). To rule out the possibility that PEG-2NPA coprecipitated with the PCL but was not actually coupled, gelpermeation chromatography (GPC) was performed on the resulting diblock copolymer ( Figure S2). A shift to higher molecular weights was observed for the PCL peak as a result of the PEG coupling, and a second peak corresponding to free PEG was notably absent. Exposure of the GPC sample containing a trace amount of water as a proton source to 365 nm light for 2 h induced a shift back toward the lowermolecular-weight PCL, and the evolution of a second peak corresponding to liberated PEG was observed.Assembly of polymersomes was accomplished through film rehydration, sonication, and extru...

The field of biomimicry is embracing the construction of complex assemblies that imitate both biological structure and function. Advancements in the design of these mimetics have generated a growing vision for creating an artificial or proto- cell. Polymersomes are vesicles that can be made from synthetic, biological or hybrid polymers and can be used as a model template to build cell-like structures. In this perspective, we discuss various areas where polymersomes have been used to mimic cell functions as well as areas in which the synthetic flexibility of polymersomes would make them ideal candidates for a biomembrane mimetic. Designing a polymersome that comprehensively displays the behaviors discussed herein has the potential to lead to the development of an autonomous, responsive particle that resembles the intelligence of a biological cell.

We report a new method for the micropatterning of multiple proteins and cells with micrometer-scale precision. Microscope projection photolithography based on a new protein-friendly photoresist, poly(2,2-dimethoxy nitrobenzyl methacrylate-r-methyl methacrylate-r-poly(ethylene glycol) methacrylate) (PDMP), was used for the fabrication of multicomponent protein/cell arrays. Microscope projection lithography allows precise registration between multiple patterns as well as facile fabrication of microscale features. Thin films of PDMP became soluble in near-neutral physiological buffer solutions upon UV exposure and exhibited excellent resistance to protein adsorption and cell adhesion. By harnessing advantages in microscope projection photolithography and properties of PDMP thin films, we could successfully fabricate protein arrays composed of multiple proteins. Furthermore, we could extend this method for the patterning of two different types of immune cells for the potential study of immune cell interactions. This technique will in general be useful for protein chip fabrication and high-throughput cell-cell communication study.

Ototoxicity is a main dose-limiting factor in the clinical application of aminoglycoside antibiotics. Despite longstanding research efforts, our understanding of the mechanisms underlying aminoglycoside ototoxicity remains limited. Here we report the discovery of a novel stress pathway that contributes to aminoglycoside-induced hair cell degeneration. Modifying the recently developed bioorthogonal noncanonical amino acid tagging (BONCAT) method, we used click-chemistry to study the role of protein synthesis activity in aminoglycoside-induced hair cell stress. We demonstrate that aminoglycosides inhibit protein synthesis in hair cells and activate a signaling pathway similar to ribotoxic stress response, contributing to hair cell degeneration. The ability of a particular aminoglycoside to inhibit protein synthesis and to activate the c-Jun N-terminal kinase (JNK) pathway correlated well with its ototoxic potential. Finally, we report that a FDA-approved drug known to inhibit ribotoxic stress response also prevents JNK activation and improves hair cell survival, opening up novel strategies to prevent and treat aminoglycoside ototoxicity.

Methods to micropattern multiple protein components on surfaces under mild conditions are of interest for biosensing, proteomics, and fundamental studies in cell biology. Here, we report on the composition-dependent thin-film solubility behavior of o-nitrobenzyl methacrylate (oNBMA, a protected form of methacrylic acid)/methyl methacrylate (MMA)/poly(ethylene glycol) methacrylate (PEGMA) random terpolymers, materials which are promising as aqueous-processible photoresists. Over a broad range of terpolymer compositions, these materials formed initially water-insoluble films, which, upon UV irradiation, rapidly dissolved in aqueous solutions above a critical pH. This threshold pH ranged from approximately 5-7 depending upon the copolymer composition and decreased as the relative ratio of MMA to PEGMA in the copolymers decreased. In addition, in a narrow window of compositions near 35:0:65 oNBMA/MMA/PEGMA (wt ratio), an inverse behavior was observed: thin films that were initially water soluble became kinetically stable in aqueous solutions after UV exposure. The time for these films to completely dissolve was hours rather than seconds, and the rate of dissolution was both temperature- and pH-dependent. This behavior is consistent with a transient stability imparted by inter- and intramolecular hydrogen bonding in the film. Using copolymers of this composition as negative tone photoresists, we demonstrated patterning of two proteins into two discrete regions of a surface. The selective solubility of the resist copolymer allows the entire patterning process to be completed using only biological buffers as solvents and across a temperature range between 4 and 37 degrees C without subjecting either protein to ultraviolet irradiation or dehydration. These materials are thus of interest for complex surface photopatterning under mild aqueous conditions.