Tumor-penetrating iRGD facilitates penetration of poly(floxuridine-ketal)-based nanomedicine for enhanced pancreatic cancer therapy.

Efficient intratumoral penetration is essential for nanomedicine to eradicate pancreatic tumors. Although nanomedicine can enter the perivascular space of pancreatic tumors, their access to distal tumor cells, aloof from the vessels, remains a formidable challenge. Here, we synthesized an acid-activatable macromolecular prodrug of floxuridine (FUDR)-poly(FUDR-ketal), engineered a micellar nanomedicine of FUDR, and intravenously co-administered the nanomedicine with the tumor-penetrating peptide iRGD for enhanced treatment of pancreatic tumor. A FUDR-derived mono-isopropenyl ether was synthesized and underwent self-addition polymerization to afford the hydrophobic poly(FUDR-ketal), which was subsequently co-assembled with amphiphilic DSPE-mPEG into the micellar nanomedicine with size of 12 nm and drug content of 56.8 wt% using nanoprecipitation technique. The acetone-based ketal-linked poly(FUDR-ketal) was triggered by acid to release FUDR to inhibit cell proliferation. In an orthotopic pancreatic tumor model derived from KPC (KrasLSL-G12D/+; Trp53LSL-R172H/+; Pdx1-Cre) cells that overexpress neuropilin-1 (NRP-1) receptor, iRGD improved penetration of FUDR nanomedicine into tumor parenchyma and potentiated the therapeutic efficacy. Our nanoplatform, along with iRGD, thus appears to be promising for efficient penetration and activation of acid-responsive nanomedicines for enhanced pancreatic cancer therapy.

Drug content on anticancer efficacy of self-assembling ketal-linked dextran-paclitaxel conjugates.

Although polymer-drug conjugates (PDCs) show great promise as versatile drug delivery systems, no antitumor PDCs based on small-molecule drugs are currently on the market, partly because of the lack of validated design principles for PDCs. High drug content is thought to be essential for devising highly efficacious PDCs based on poorly soluble antitumor drugs, but this has not been well validated. Therefore, revisiting the relationship between drug content and PDC performance is vital. In this study, we synthesized four dextran-paclitaxel (PTX) conjugates (designated as DKPs) with different drug contents by linking dextran and PTX via an acid-responsive ketal, and we used the conjugates to construct self-assembled DKP nanoparticles (NPs) for antitumor therapy. We focused on how PTX content influenced the hydrolysis kinetics, cytotoxicity, cellular uptake and intracellular hydrolysis, pharmacokinetics, biodistribution, and antitumor efficacies of the DKP NPs. We found that DKP NPs with lower PTX content showed accelerated drug release and increased tumor accumulation, and consequently enhanced antitumor efficacy. In 4T1-Luc and Panc02-Luc cancer models, the NPs showed considerably improved therapeutic efficacy than the micellar formulation of PTX that is currently in clinical use. Our results indicate that DKP NPs with lower PTX content possess greater antitumor potential, and our findings offer new insights for the connection of drug content-formulation-bioactivity relationship in the rational design of PDC prodrugs.

Fine-tuning the sequential drug release of nano-formulated mutual prodrugs dictates the combination effects.

The maintenance of robust ratiometric loading of dual therapeutic agents and fine-tuning release kinetics for consistent in vitro and in vivo optimization of combination effects is vital for discovering new anticancer drug combinations and remains challenging. Smart nanomedicine strategies have been investigated for this purpose, but most of the reported strategies focus either on ratiometric delivery or on unimodal sequential release of the two different agents, which hampers effective optimization of combination effects. Herein we report a sequential drug release system based on nanoformulated mutual prodrugs constructed by the formation of ketal linkages with different acid sensitivities, thus enabling the acid-triggered release of two anticancer drugs, paclitaxel and gemcitabine, in various sequences. We found that in several cell lines, the sequence of drug release substantially affected the combination effects; specifically, in A549 cells, time-staggered release profiles showed enhanced synergistic effects relative to those of a simultaneous release profile. Moreover, in vivo assessment of the antitumor efficacy of the nanoformulations in A549 xenograft models indicated that the best therapeutic effects were obtained with time-staggered release profiles, which was consistent with the in vitro results. Our strategy for precisely controlled sequential drug release can be expected to facilitate the screening of optimal drug combinations and maximize combination effects both in vitro and in vivo.

Stromal Homeostasis-Restoring Nanomedicine Enhances Pancreatic Cancer Chemotherapy.

The desmoplastic stroma imposes a fatal physical delivery barrier in pancreatic ductal adenocarcinoma (PDAC) therapy. Deconstructing the stroma components hence predominates in stroma-targeting approaches, but conflicting outcomes have sometimes occurred due to the multifaceted nature of the stroma. Here, we constructed two sub-20-nm nanomedicines based on a so-called "next-wave" antifibrotic halofuginone (HF) and the tumoricidal paclitaxel (PTX) for enhanced PDAC chemotherapy. This was achieved by coassembling methoxy poly(ethylene glycol)-b-poly(caprolactone) with ketal-linked HF- and PTX-derived prodrugs. HF nanomedicine and PTX nanomedicine had excellent prodrug-nanocarrier compatibility and exhibited greatly improved pharmacokinetic profiles and high tumor accumulation. HF nanomedicine pretreatment restored stromal homeostasis and considerably facilitated the distribution of PTX nanomedicine and its penetration into carcinoma cells, leading to positive modulation of the infiltration of cytotoxic T cells and significant regression of tumor growth in two PDAC models. Our nanomedicine-based stromal remodeling strategy appears promising for treating desmoplastic malignancies.

Carrier strategies boost the application of CRISPR/Cas system in gene therapy.

Emerging clustered regularly interspaced short palindromic repeat/associated protein (CRISPR/Cas) genome editing technology shows great potential in gene therapy. However, proteins and nucleic acids suffer from enzymatic degradation in the physiological environment and low permeability into cells. Exploiting carriers to protect the CRISPR system from degradation, enhance its targeting of specific tissues and cells, and reduce its immunogenicity is essential to stimulate its clinical applications. Here, the authors review the state-of-the-art CRISPR delivery systems and their applications, and describe strategies to improve the safety and efficacy of CRISPR mediated genome editing, categorized by three types of cargo formats, that is, Cas: single-guide RNA ribonucleoprotein, Cas mRNA and single-guide RNA, and Cas plasmid expressing CRISPR/Cas systems. The authors hope this review will help develop safe and efficient nanomaterial-based carriers for CRISPR tools.

Modular ketal-linked prodrugs and biomaterials enabled by organocatalytic transisopropenylation of alcohols.

Isopropenyl ethers are critical intermediates for accessing medicinally valuable ketal-based prodrugs and biomaterials, but traditional approaches for the synthesis of isopropenyl ethers suffer from poor functional group compatibility and harsh reaction conditions. Here, we develop an organocatalytic transisopropenylation approach to solve these challenges, enabling the synthesis of isopropenyl ethers from various hydroxyl-group-containing small-molecule drugs, polymers, and functional building blocks. The method provides a straightforward and versatile synthesis of isopropenyl ethers, features excellent tolerance of diverse functional groups, applies to a wide range of substrates, and allows scalable synthesis. The development of this organocatalytic transisopropenylation approach enables access to modular preparation of various acid-sensitive ketal-linked prodrugs and functionalized ketalated biomaterials. We expect our syntheses and transformations of isopropenyl ethers will find utility in several diverse fields, including medicinal chemistry, drug delivery, and biomaterials.

Acid-sensitive PEGylated paclitaxel prodrug nanoparticles for cancer therapy: Effect of PEG length on antitumor efficacy.

Paclitaxel is one of the most widely used anticancer agents, but strong side effects and low bioavailability limit its clinical efficacy. The use of tumor microenvironment-responsive prodrugs is promising to solve these problems, and a smart linkage is crucial to achieve the efficient release of paclitaxel from such prodrugs in tumor. Herein, an acid-responsive acetone-based acyclic ketal linkage is used to construct paclitaxel prodrugs with different length of poly(ethylene glycol) (PEG). The PEGylated acetone-based acyclic-ketal-linked prodrugs of paclitaxel (PKPs) self-assembled into nanoparticles that were stable in normal physiological environment but released paclitaxel rapidly in mildly acidic environment in tumor. The length of PEG had considerable impact on size and critical micelle concentration of PKP nanoparticles, thereby affecting prodrug hydrolysis kinetics, pharmacokinetics, biodistribution, and antitumor activity for PKP nanoparticles. In an A2780 xenograft mouse model, PKP nanoparticles displayed improved pharmacokinetics and superior antitumor efficacy against Taxol. Our results demonstrate that acyclic-ketal-based prodrugs are useful for the development of acid-responsive anticancer nanomedicines.

Modular Acid-Activatable Acetone-Based Ketal-Linked Nanomedicine by Dexamethasone Prodrugs for Enhanced Anti-Rheumatoid Arthritis with Low Side Effects.

Given the physically encapsulated payloads with drug burst release and/or low drug loading, it is critical to initiate an innovative prodrug strategy to optimize the design of modular nanomedicines. Here, we designed modular pH-sensitive acetone-based ketal-linked prodrugs of dexamethasone (AKP-dexs) and formulated them as nanoparticles. We comprehensively studied the relationships between AKP-dex structure and properties, and we selected two types of AKP-dex-loaded nanoparticles for in vivo studies on the basis of their size, drug loading, and colloidal stability. In a collagen-induced arthritis rat model, these AKP-dex-loaded nanoparticles showed higher accumulation in inflamed joints and better therapeutic efficacy than free dexamethasone phosphate with less-severe side effects. AKP-dex-loaded nanoparticles may be useful for treating other inflammatory diseases and thus have great translational potential. Our findings represent an important step toward the development of practical applications for acetone-based ketal-linked prodrugs and are useful in the design of modular nanomedicines.

Acid-Triggered Release of Native Gemcitabine Conjugated in Polyketal Nanoparticles for Enhanced Anticancer Therapy.

Nucleoside analogue drugs are widely used in cancer therapy and antiviral therapy, while fast metabolism, drug resistance, and severe side effects significantly limit their clinical applications. To address these issues, a variety of ester- and amide-linked prodrugs and their nanoparticulate formulations have been devised. However, most of these prodrugs suffer from inefficient transformation to native drugs in tumor. Here, we report an approach to conjugate gemcitabine, a kind of anticancer nucleoside drug and widely used to treat cancers, to polyketal backbone via pH-sensitive ketal linkage, and prepared gemcitabine-containing polyketal prodrug nanoparticles with minimal drug release under physiological conditions and acid-triggerable release of native gemcitabine. Intracellular and intratumoral degradation of the pH-sensitive gemcitabine-containing polyketal prodrug and incorporation of gemcitabine into DNA were confirmed by confocal microscopy using EdU, an analogue of gemcitabine. One single intravenous injection of these gemcitabine-containing polyketal prodrug nanoparticles demonstrated notable anticancer efficacy in the A2780 ovarian xenograft tumor model with increased survival rate and good safety. Our approach can be adopted for other diol nucleoside analogues to synthesize pH-sensitive nucleoside-polyketal prodrugs for developing anticancer and antiviral formulations.

Optimization of technology for dietary fiber extraction from Maixiansan by response surface methodology.

BACKGROUND: Our study aims to determine whether response surface methodology can optimize the extraction of dietary fiber from Maixiansan. METHODS: A Box-Behnken design was employed to optimize the extraction parameters, including α-amylase concentration (X1: 0.3 - 0.5%), enzymolysis time (X2: 30 - 60 min) and NaOH content (X3: 1.0 - 5.0%), of dietary fiber from Maixiansan using an enzyme-alkali extraction technique. RESULTS: The optimal technological conditions were as follows: α-amylase concentration: 0.4%; enzymolysis time: 45 min; NaOH content: 4.0%. Under these conditions, the extraction yield reached 57.14%, which was well consistent with the predicted models with a coefficient of determination (R2) of 0.9818. An evaluation of the anti-inflammatory activity indicated that Maixiansan was able to significantly inhibit dextran sodium sulfate-induced ulcerative colitis in rats by increasing the concentration of short-chain fatty acids (acetate, propionate and butyrate), among which the butyrate content was significantly higher in the Maixiansan group than in the other groups. CONCLUSION: Our experiments showed that response surface methodology can optimize the extraction of dietary fiber from Maixiansan. Maixiansan could be explored as an anti-ulcerative colitis agent.