A Polymer-Based Antigen Carrier Activates Two Innate Immune Pathways for Adjuvant-Free Subunit Vaccines.

The activation of multiple Pattern Recognition Receptors (PRRs) has been demonstrated to trigger inflammatory responses and coordinate the host's adaptive immunity during pathogen infections. The use of PRR agonists as vaccine adjuvants has been reported to synergistically induce specific humoral and cellular immune responses. However, incorporating multiple PRR agonists as adjuvants increases the complexity of vaccine design and manufacturing. In this study, we discovered a polymer that can activate both the Toll-like receptor (TLR) pathway and cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. The polymer was then conjugated to protein antigens, creating an antigen delivery system for subunit vaccines. Without additional adjuvants, the antigen-polymer conjugates elicited strong antigen-specific humoral and cellular immune responses. Furthermore, the antigen-polymer conjugates, containing the Receptor Binding Domain (RBD) of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike Protein or the Monkeypox Antigen M1R as the antigens, were found to induce potent antigen-specific antibodies, neutralizing antibodies, and cytotoxic T cells. Immunization with M1R-polymer also resulted in effective protection in a lethal challenge model. In conclusion, this vaccine delivery platform offers an effective, safe, and simple strategy for inducing antigen-specific immunity against infectious diseases.

Research advance of natural products in tumor immunotherapy.

Cancer immunotherapy has emerged as a novel anti-tumor treatment. Despite significant breakthroughs, cancer immunotherapy remains focused on several types of tumors that are sensitive to the immune system. Therefore, effective strategies to expand its indications and improve its efficacy become key factors for the further development of cancer immunotherapy. In recent decades, the anticancer activities of natural products are reported to have this effect on cancer immunotherapy. And the mechanism is largely attributed to the remodeling of the tumor immunosuppressive microenvironment. The compelling data highlight that natural products offer an alternative method option to improve immune function in the tumor microenvironment (TME). Currently, more attention is being paid to the discovery of new potential modulators of tumor immunotherapy from natural products. In this review, we describe current advances in employing natural products and natural small-molecule drugs targeting immune cells to avoid tumor immune escape, which may bring some insight for guiding tumor treatment.

Bridgehead Alkene-Enabled Strain-Driven Bioorthogonal Reaction.

Herein, we report a novel bioorthogonal reaction that hinges on a bridgehead alkene (BHA)-enabled inverse-electron-demand Diels-Alder (IEDDA) cycloaddition. Readily accessible from natural product ß-caryophyllene, the strained BHA displays high reactivity toward the IEDDA reaction while maintaining excellent biocompatibility. The developed IEDDA reaction has been applied to in vitro protein labeling and pretargeted live cell imaging.

Chemical trigger-enabled bioconjugation reaction.

Development of conceptually novel and practically useful bioconjugation reactions has been an intense pursuit of chemical biology research. Herein, we report an unprecedented bioconjugation reaction that hinges on a chemical trigger-enabled inverse-electron-demand Diels-Alder (IEDDA) cycloaddition of trans-cycloheptene (TCH) with tetrazine. Unlike the conventional strain-promoted bioconjugation reactions that utilize built-in strained alkenes as reactants, the current one features a "trigger-release-conjugate" reaction model, in which a highly strained TCH species is released from a bench-stable bicyclic N-nitrosourea (BNU) derivative upon treatment with an external stimulus. It is noteworthy that the reactivity-stability balance of BNU derivatives could be tuned by manipulating their N-1 substituents. As a proof-of-concept case, this new chemical trigger-enabled IEDDA reaction has been applied to in vitro protein labeling and pretargeted cell imaging. This work opens a new avenue to utilize BNU derivatives as a new class of chemical reporters in bioconjugate chemistry.

Synergetic Tumor Probes for Facilitating Therapeutic Delivery by Combined-Functionalized Peptide Ligands.

Both targeting and penetrating ability are the key characteristics for tissue probing and precise delivery. To construct an efficient nano probing and delivery system toward human epidermal growth factor receptor 2 (HER2) positive cancer, we established a nano liposomal system functionalized with a newly screened HER2 targeting peptide (HP2, YDLKEPEH) and the cell-penetrating peptide TAT simultaneously. Compared with the monofunctionalized liposomal probes, the dual-functional ones demonstrated a synergetic effect in cell uptake, drug delivery, and in vivo imaging. The improved efficacy of the synergetic system provides a prospective strategy for cancer diagnosis and therapy.

"Turn-On" Activatable AIE Dots for Tumor Hypoxia Imaging.

A hypoxia-responsive fluorescence probe of amphiphilic PEGylated azobenzene caged tetraphenylethene (TPE) for tumor cell imaging is reported; it possesses excellent solubility in aqueous medium due to the easy formation of micelles by self-assembly. The fluorescence resonance energy transfer (FRET) process ensures that the fluorescence of the azobenene caged AIE fluorogen is quenched efficiently. When cultured with tumor cells, the azo-bond is reduced under hypoxia conditions and the fluorescence of AIE fluorogen recovers dramatically. Besides using UV light, NIR light can also be used as the excited light resource to generate the fluorescence due to the two-photon fluorescence imaging process.

MMP-2-Controlled Transforming Micelles for Heterogeneic Targeting and Programmable Cancer Therapy.

Herein, through the active-peptide-functionalization, we developed a nanoscale micelles system (named HEKM) which consists of tumor microenvironment-regulated shape-changing with specific recognition abilities for enhanced cellular targeting, internalization and therapy of heterogeneic tumors. As a result, HEKMs could recognize and bind the tumor heterogeneity marker EGFR-HER2 complex, which led to an enhanced tumor targeting effect. In particular, HEKMs could self-assemble into nanorods under normal physiological conditions while transform into nanospheres in the tumor extracellular microenvironment by a sensitive response to matrix metalloproteinase-2 (MMP-2). The nanorods could prolong the blood circulation time while the nanospheres could accelerate tissue penetration in tumors. In vivo dual-modal targeted imaging was realized by FRET-fluorophore conjugation and gadolinium loading in HEKMs. Tumor cell apoptosis was achieved by proapoptotic element integration. The in vitro and in vivo studies both demonstrated that these rationally designed, shape-changing and targeting micelles could achieve maximized drug efficacy and minimum side effects.

pH-Triggered Peptide Self-Assembly for Targeting Imaging and Therapy toward Angiogenesis with Enhanced Signals.

Mild acidic environment and angiogenesis are two typical characteristics of tumor. The specific response toward both lower pH and angiogenesis may enhance the targeting ability both for drug and diagnostic probe delivery. Herein, we present a kind of dual responding self-assembled nanotransformation material that is tumor angiogenesis targeting and pH triggered based on amphiphilic conjugation between peptides (STP) and aromatic molecules (tetraphenylethylene (TPE)). The morphology of the self-assembled peptide conjugates is responsibly changed from nanoparticles in neutral condition to nanofibers in acidic condition, which "turn on" the in vivo targeting imaging and accelerate the efficient drug delivery and in vivo therapy. On the basis of the well-controlled nanotransformation both in vitro and in vivo, we envisioned the successful demonstration of the responding materials would open a new avenue in turn on targeting imaging diagnostics and specific cancer therapeutics.

Targeting peptide functionalized liposomes towards aminopeptidase N for precise tumor diagnosis and therapy.

Aminopeptidase N (APN/CD13) is closely related to the growth of cancers and is suggested as a suitable target for anti-cancer therapy. Based on the "one-bead-one-compound" (OBOC) approach on a microarray device, we screened out a novel affinity peptide LN (YEVGHRC). It was determined that LN could specifically recognize and bind to APN. Moreover, LN-functionalized liposomes (LN-LS) could achieve efficient nano-encapsulated drug delivery under APN-overexpressing tumor conditions in vitro and in vivo. We expect that LN-LS could provide a new strategy for APN-positive tumor diagnosis and therapy.

Switchable Liposomes: Targeting-Peptide-Functionalized and pH-Triggered Cytoplasmic Delivery.

One switchable nanodelivery system was constructed. Liposomes were functionalized by a novel dual-recognition peptide STP, which is pH-responsive as well as the affinity ligand of tumor marker VEGFR2 (the angiogenesis marker vascular endothelial growth factor receptor 2). Efficient drug delivery and in vivo therapy could be "turned on" and accelerated only in the conditions of VEGFR2 overexpression and a mild acidic environment. We envisioned that the successful demonstration of this switchable nanocarrier system would open a new avenue on rapid cytoplasmic delivery for specific cancer diagnostics and therapeutics.

HER2 Targeting Peptides Screening and Applications in Tumor Imaging and Drug Delivery.

Herein, computational-aided one-bead-one-compound (OBOC) peptide library design combined with in situ single-bead sequencing microarray methods were successfully applied in screening peptides targeting at human epidermal growth factor receptor-2 (HER2), a biomarker of human breast cancer. As a result, 72 novel peptides clustered into three sequence motifs which are PYL***NP, YYL***NP and PPL***NP were acquired. Particularly one of the peptides, P51, has nanomolar affinity and high specificity for HER2 in ex vivo and in vivo tests. Moreover, doxorubicin (DOX)-loaded liposome nanoparticles were modified with peptide P51 or P25 and demonstrated to improve the targeted delivery against HER2 positive cells. Our study provides an efficient peptide screening method with a combination of techniques and the novel screened peptides with a clear binding site on HER2 can be used as probes for tumor imaging and targeted drug delivery.

Micromixer Based Preparation of Functionalized Liposomes and Targeting Drug Delivery.

We present here a specific targeting nanocarrier system by functionalization of liposomes with one new type of breast cancer targeting peptide (H6, YLFFVFER) by a micromixer with high efficiency. Antitumor drugs could be successfully delivered into human epidermal growth factor receptor 2 (HER2) positive breast cancer cells with high efficiency in both in vivo and ex vivo models.

Switchable probes: pH-triggered and VEGFR2 targeted peptides screening through imprinting microarray.

One switchable affinity peptide, STP, is screened out from a high-throughput library by an integrated imprinting microarray. STP is pH triggered and also the ligand of the marker VEGFR2. Efficient cell recognition and penetration as well as an in vivo image could be "turned on" and accelerated only in the condition of VEGFR2 overexpression and a mild acidic environment.

Peptide functionalized targeting liposomes: for nanoscale drug delivery towards angiogenesis.

A novel affinity peptide S1 (LIDHEWKENYFPLSF) was screened out via a "one bead one compound" (OBOC) approach on a microarray device. It was identified that S1 could specifically recognize and bind to vascular endothelial growth factor receptor 2 (VEGFR2), which is an angiogenesis biomarker. Moreover, S1-functionalized liposomes (S1-LS) could achieve efficient nanoscale drug delivery under the conditions of VEGFR2-overexpression in vitro and in vivo. It was demonstrated that S1-LS would be a promising VEGFR2-targeting drug delivery system.