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Core cross-linked polymeric micelles (CCPMs) are designed to improve the therapeutic profile of hydrophobic drugs, reduce or completely avoid protein corona formation, and offer prolonged circulation times, a prerequisite for passive or active targeting. In this study, we tuned the CCPM stability by using bifunctional or trifunctional cross-linkers and varying the cross-linkable polymer block length. For CCPMs, amphiphilic thiol-reactive polypept(o)ides of polysarcosine- block -poly( S -ethylsulfonyl-l-cysteine) [pSar- b -pCys(SO 2 Et)] were employed. While the pCys(SO 2 Et) chain lengths varied from X n = 17 to 30, bivalent (derivatives of dihydrolipoic acid) and trivalent (sarcosine/cysteine pentapeptide) cross-linkers have been applied. Asymmetrical flow field-flow fraction (AF4) displayed the absence of aggregates in human plasma, yet for non-cross-linked PM and CCPMs cross-linked with dihydrolipoic acid at [pCys(SO 2 Et)] 17 , increasing the cross-linking density or the pCys(SO 2 Et) chain lengths led to stable CCPMs. Interestingly, circulation time and biodistribution in mice of non-cross-linked and bivalently cross-linked CCPMs are comparable, while the trivalent peptide cross-linkers enhance the circulation half-life from 11 to 19 h.

Photoswitchable materials are important in broad applications. Recently appeared inorganic photoswitchable upconversion nanoparticles (PUCNPs) become a competitive candidate to surmount the widespread issue of the organic counterparts -photobleaching. However, current PUCNPs follow solely Yb 3+ /Nd 3+ cosensitizing mode, which results in complex multilayer doping patterns and imperfectness of switching in UV-blue region. In this work, we have adopted a new strategy to construct Nd 3+ free PUCNPs-NaErF 4 @NaYF 4 @NaYbF 4 :0.5%Tm@NaYF 4 . These PUCNPs demonstrate the superior property of photoswitching. A prominent UV-blue emission from Tm 3+ is turned on upon 980 nm excitation, which can be completely turned off by 800 nm light. The quasi-monochromatic red upconversion emission upon 800 nm excitation-a distinct feature of undoping NaErF 4 upconversion system-endows the PUCNPs with promising image-guided photoinduced "off-on" therapy in biomedicine. As a proof-of-concept we have demonstrated the imaging-guided photodynamic therapy (PDT) of cancer, where 800 nm excitation turns off the UV-blue emission and leaves the emission at 660 nm for imaging. Once the tumor site is targeted, excitation switching to 980 nm results in UV-blue emission and the red emission. The former is used to induce PDT, whereas the latter is to monitor the therapeutic process. Our study implies that this upconversion photoswitching material is suitable for real-time imaging and image-guided therapy under temporal and spatial control.

The ability to assess in near-real time the tumor cell killing efficacy of chemotherapy regimens would improve patient treatment and survival. An ineffective regimen could be abandoned early in favor of a more effective treatment. We sought to noninvasively image treatment-related tumor cell death in mice using an optically labeled synthetic heat shock protein-90 (Hsp90) alkylator, 4-(N-(S-glutathionylacetyl)amino)phenylarsonous acid (GSAO). The Hsp90 chaperone is an important element in oncogene addiction and tumor cell survival, and its expression is enhanced by chemotherapy. These factors were predicted to favor the detection of tumor cell death using GSAO. GSAO specifically labeled apoptotic and necrotic tumor cells in culture and cells of comparable morphology in subcutaneous human pancreatic carcinoma tumors in mice. A near-infrared fluorescent conjugate of GSAO was used to noninvasively image cyclophosphamide-induced tumor cell death in murine orthotopic human mammary tumors. The GSAO conjugate did not accumulate in healthy organs or tissues in the mouse, and unbound compound was excreted rapidly via the kidneys. There was a significant increase in the GSAO fluorescence signal in the treated tumors measured either in vivo or ex vivo, and the fluorescence signal colocalized with apoptotic cells in sectioned tumors. The favorable biodistribution of optically labeled GSAO, the nature of its tumor cell target, and its capacity to noninvasively detect tumor cell death should facilitate the application of this compound in studies of the efficacy of existing and new chemotherapeutics.

Traumatic brain injury is characterized by initial tissue damage, which then can lead to secondary processes such as cell death and blood-brain-barrier disruption. Clinical and preclinical studies of traumatic brain injury typically employ anatomical imaging techniques and there is a need for new molecular imaging methods that provide complementary biochemical information. Here, we assess the ability of a targeted, near-infrared fluorescent probe, named PSS-794, to detect cell death in a brain cryolesion mouse model that replicates certain features of traumatic brain injury. In short, the model involves brief contact of a cold rod to the head of a living, anesthetized mouse. Using noninvasive whole-body fluorescence imaging, PSS-794 permitted visualization of the cryolesion in the living animal. Ex vivo imaging and histological analysis confirmed PSS-794 localization to site of brain cell death. The nontargeted, deep-red Tracer-653 was validated as a tracer dye for monitoring blood-brain-barrier disruption, and a binary mixture of PSS-794 and Tracer-653 was employed for multicolor imaging of cell death and blood-brain-barrier permeability in a single animal. The imaging data indicates that at 3 days after brain cryoinjury the amount of cell death had decreased significantly, but the integrity of the blood-brain-barrier was still impaired; at 7 days, the blood-brain-barrier was still three times more permeable than before cryoinjury.

Entrapment of antigens in mucoadhesive nanoparticles prepared from N-trimethyl chitosan (TMC) has been shown to increase their immunogenicity. However, because of their large size compared to soluble antigens, particles poorly diffuse through the nasal epithelium. The aim of this work was to study whether nasal vaccination with a much smaller TMC-antigen nanoconjugate would result in higher antibody responses as compared to TMC nanoparticles. TMC was covalently linked to a model antigen, ovalbumin (OVA), using thiol chemistry. For comparison, TMC/OVA nanoparticles and solutions of OVA and a physical mixture of TMC and OVA were made. As shown previously for TMC/OVA nanoparticles, TMC-OVA conjugate prolonged the nasal residence time of the antigen. TMC-OVA conjugate diffused significantly better through a monolayer of lung carcinoma (Calu-3) cells than TMC/OVA nanoparticles did. Moreover, nasal immunization of mice with the conjugate resulted in significantly more OVA positive DCs in the cervical lymph nodes as compared to TMC/OVA nanoparticles. Mice nasally immunized with TMC-OVA conjugate produced high levels of secretory IgA in nasal washes and higher titers of OVA-specific IgG than mice immunized with TMC/OVA nanoparticles after a priming dose. Moreover, as compared to TMC/OVA nanoparticles, TMC-OVA conjugate induced a more balanced IgG1/IgG2a response. In conclusion, the TMC-antigen nanoconjugate improves nasal delivery and immunogenicity of the antigen. This suggests that efficient codelivery of antigen and adjuvant to DCs, rather than a particulate form of the antigen/adjuvant combination, is decisive for the immunogenicity of the antigen.