Two types of water-soluble molecular brushes with a poly(3-phenylthiophene) (PPT) backbone tethering poly(ethylene glycol) (PEG) and zwitterionic poly(carboxybetaine) (PCB) side chains were synthesized and named PPTPEG and PPTPCB, respectively. Atomic force microscopy observations demonstrated their wormlike morphology with a length range of 5–33 nm. The two types of molecular brushes had similar emission spectra covering 500–800 nm with a maximal emission wavelength of about 590 nm in water. The fluorescence signals falling in 650–800 nm could penetrate deeper in tissues and improve the imaging properties of the brushes when they were used as optical probes. PPTPEG and PPTPCB brushes could be internalized by cells through caveolae-mediated endocytosis. The effects of PEG and PCB side chains of the brushes on their biological properties were compared, showing that the PCB side chain was favorable to the cellular uptake, tumor penetration and tumor targeting of the molecular brushes.

Herein, thermo and pH dual-responsive drug-linked pseudo-polypeptide micelles were prepared by a self-assembly strategy. Initially, a temperature-responsive comb-shaped poly(2-isopropyl-2-oxazoline)-b-linear poly(acrylic acid) block copolymer (CPiPrOx-b-PAA) was synthesized through a combination of living cationic ring-opening polymerization and living radical polymerization. Subsequently, conjugation of doxorubicin (DOX) with the linear PAA block through a pH-responsive acylhydrazone bond led to a block copolymer having an amphiphilic characteristic, and this block copolymer then self-assembled into CPiPrOx-b-PAA-DOX micelles. TEM and DLS measurements showed that the CPiPrOx-b-PAA-DOX micelles had a uniform spherical morphology with a solid size of about 50 nm and a hydrodynamic size of about 123 nm. Moreover, the micelle coating of comb-shaped poly(2-isopropyl-2-oxazoline) displayed a temperature-responsive behavior with a phase transition temperature of 45 °C. The CPiPrOx-b-PAA-DOX micelles showed a pH-responsive DOX release in vitro; this confirmed the acid-liable effect of the acylhydrazone bond that linked the linear PAA block with DOX. In in vitro cell test, a dose-dependent cytotoxicity and caveolae-mediated endocytosis of the CPiPrOx-b-PAA-DOX micelles were observed. Based on near-infrared fluorescence (NIRF) imaging, a significant tumor accumulation of the CPiPrOx-b-PAA-DOX micelles was observed when the dye-labeled CPiPrOx-b-PAA-DOX micelles were intravenously injected into H22 tumor-bearing mice.

We report a strategy to significantly improve tumor penetration of nanomedicines by using size-minimized and zwitterionic nanocarriers. We synthesized a series of 21-arm star block copolymers with the hydrodynamic diameter of 10–40 nm and conjugated doxorubicin to the copolymers through pH-sensitive acylhydrazone linkages. The zwitterionic poly(carboxybetaine) (PCB), nonionic polyethylene glycol (PEG) and phenylboronic acid-incorporated PCB were selected as the peripherial hydrophilic blocks of the copolymers, respectively. We demonstrated that the size-minimized multiarm copolymer with PCB surface showed stronger tumor permeability when compared to the copolymers with PEG surface or larger size. The drug-conjugated multiarm copolymer that has the longest blood circulation time did not achieve the highest tumor accumulation. The incorporation of phenylboronic acid group into the peripherial block of the drug-conjugated multiarm copolymer significantly enhanced their cytotoxicity, cellular uptake, tumor accumulation, tumor permeability and antitumor activity.The effects of size, hydrophilic block and targeting moiety on tumor accumulation and tumor penetration of the 21 arm star block copolymers were investigated in cellular and tissue levels.

To understand the size effect of polymeric micelles on their biological properties, such as cellular uptake, biodistribution, tumor accumulation, and so on, we prepared a series of doxorubicin (DOX)-loaded protoporphyrin (PP)-poly(ε-caprolactone) (PCL)-poly(ethylene glycol) (PEG) micelles with different diameters (40, 70, 100, and 130 nm). The incorporation of the protoporphyrin moiety enhanced the stability of the micelles and provided luminescent capability that is useful in the investigation of the cellular uptake of the micelles by fluorescence imaging. The biodistributions of the micelles in mice bearing tumors were evaluated by near-infrared fluorescence imaging and DOX concentration measurements in different tissues. The in vitro and in vivo investigations demonstrated the pronounced dependence of the cellular uptake, biodistribution, and antitumor effectiveness of the micelles on their size.Keywords: biodistribution; cellular uptake; polymeric micelles; protoporphyrin; size dependence

Dendrimers have several featured advantages over other nanomaterials as drug carriers, such as well-defined structure, specific low-nanometer size, and abundant peripheral derivable groups, etc. However, these advantages have not been fully exploited yet to optimize their biological performance, especially tumor penetration, which is a shortcoming of current nanomaterials. Here we show the syntheses of a new class of oligo(ethylene glycol) (OEG)-based thermosensitive dendrimers up to the fourth generation. Each dendrimer shows monodisperse structure. OEG/poly(ethylene glycol) (PEG) moieties with different precise lengths were introduced to the periphery of the fourth-generation dendrimer followed by an antitumor agent, gemcitabine (GEM). The biodistributions of the GEM-conjugated dendrimers were investigated by micro positron emission tomography and multispectral optoacoustic tomography imaging techniques and compared with that of GEM-conjugated poly(amidoamine) (PAMAM). The GEM-conjugated dendrimer with the longest peripheral PEG segments exhibited the most desirable tumor accumulation and penetration and thus had significantly higher antitumor activity than the GEM-conjugated PAMAM.

40 nm-sized boronic acid-rich protein nanoparticles composed of bovine serum albumin and poly(N-3-acrylamidophenylboronic acid) were prepared by polymerizing N-3-acrylamidophenylboronic acid in the presence of albumin. The content of boronic acid-containing poly(N-3-acrylamidophenylboronic acid) in the nanoparticles can be tuned from 80% to 32% at constant nanoparticle size. When used to deliver doxorubicin in vivo, such sized nanoparticles show dominantly liver-targeting, and significant washout-resistant ability compared to those boronic acid-absent nanoparticles due to the interaction between sialic acid residues in the liver and boronic acid groups in the nanoparticles. The sialic acid overexpression on hepatic H22 tumor cells is demonstrated to be much higher than that on hepatocytes, resulting in the preferential accumulation of boronic acid-rich nanoparticles in liver cancer cells. In vivo antitumor examination in orthotopic liver cancer model shows that these doxorubicin-loaded nanoparticles not only have significantly superior ability in impeding tumor growth, but also induce distinct tumor regression with no hepatic and cardiac toxicities.Doxorubicin was encapsulated in boronic acid-rich protein nanoparticles. In vivo antitumor examination in orthotopic liver cancer shows that these nanoparticles make tumor regression distinctly.

Giant multiarm polymers with and without β-cyclodextrin (β-CD) end groups were synthesized. Further, the former was assembled into nanoparticles via a β-CD/adamantane inclusion complex. The incorporation of an esterase-sensitive linker in the inclusion complex enables the nanoparticles to decompose to the multiarm polymer again through the hydrolysis of ester linkage, making the nanoparticles have the characteristics of multistage nanovectors.

The in vivo behaviors of doxorubicin (DOX)-loaded dextran-poly(3-acrylamidophenylboronic acid) (Dextran-PAPBA) nanoparticles (NPs) were studied. The DOX-loaded NPs had a narrowly distributed diameter of ca. 74 nm and mainly accumulated in liver of tumor-bearing mice after intravenous injection as demonstrated by in vivo real-time near infrared fluorescent imaging. The DOX contents in various tissues were quantified and consisted well with the results of fluorescent imaging. The biodistribution pattern of DOX-loaded NPs encourages us to investigate their liver tumor treatment by using an orthotopically implanted liver tumor model, revealing that the DOX-loaded NPs formulation had better antitumor effect than free DOX.