FRET-enabled monitoring of the thermosensitive nanoscale assembly of polymeric micelles into macroscale hydrogel and sequential cognate micelles release

Advancements and Applications of Injectable Hydrogel Composites in Biomedical Research and Therapy

Injectable hydrogels have gained popularity for their controlled release, targeted delivery, and enhanced mechanical properties. They hold promise in cardiac regeneration, joint diseases, postoperative analgesia, and ocular disorder treatment. Hydrogels enriched with nano-hydroxyapatite show potential in bone regeneration, addressing challenges of bone defects, osteoporosis, and tumor-associated regeneration. In wound management and cancer therapy, they enable controlled release, accelerated wound closure, and targeted drug delivery. Injectable hydrogels also find applications in ischemic brain injury, tissue regeneration, cardiovascular diseases, and personalized cancer immunotherapy. This manuscript highlights the versatility and potential of injectable hydrogel nanocomposites in biomedical research. Moreover, it includes a perspective section that explores future prospects, emphasizes interdisciplinary collaboration, and underscores the promising future potential of injectable hydrogel nanocomposites in biomedical research and applications.

FRET Based Biosensor: Principle Applications Recent Advances and Challenges

Förster resonance energy transfer (FRET)-based biosensors are being fabricated for specific detection of biomolecules or changes in the microenvironment. FRET is a non-radiative transfer of energy from an excited donor fluorophore molecule to a nearby acceptor fluorophore molecule. In a FRET-based biosensor, the donor and acceptor molecules are typically fluorescent proteins or fluorescent nanomaterials such as quantum dots (QDs) or small molecules that are engineered to be in close proximity to each other. When the biomolecule of interest is present, it can cause a change in the distance between the donor and acceptor, leading to a change in the efficiency of FRET and a corresponding change in the fluorescence intensity of the acceptor. This change in fluorescence can be used to detect and quantify the biomolecule of interest. FRET-based biosensors have a wide range of applications, including in the fields of biochemistry, cell biology, and drug discovery. This review article provides a substantial approach on the FRET-based biosensor, principle, applications such as point-of-need diagnosis, wearable, single molecular FRET (smFRET), hard water, ions, pH, tissue-based sensors, immunosensors, and aptasensor. Recent advances such as artificial intelligence (AI) and Internet of Things (IoT) are used for this type of sensor and challenges.

Physically stimulus-responsive nanoparticles for therapy and diagnosis

Nanoparticles offer numerous advantages in various fields of science, particularly in medicine. Over recent years, the use of nanoparticles in disease diagnosis and treatments has increased dramatically by the development of stimuli-responsive nano-systems, which can respond to internal or external stimuli. In the last 10 years, many preclinical studies were performed on physically triggered nano-systems to develop and optimize stable, precise, and selective therapeutic or diagnostic agents. In this regard, the systems must meet the requirements of efficacy, toxicity, pharmacokinetics, and safety before clinical investigation. Several undesired aspects need to be addressed to successfully translate these physical stimuli-responsive nano-systems, as biomaterials, into clinical practice. These have to be commonly taken into account when developing physically triggered systems; thus, also applicable for nano-systems based on nanomaterials. This review focuses on physically triggered nano-systems (PTNSs), with diagnostic or therapeutic and theranostic applications. Several types of physically triggered nano-systems based on polymeric micelles and hydrogels, mesoporous silica, and magnets are reviewed and discussed in various aspects.

Thermoresponsive Self-Assembly of Twofold Fluorescently Labeled Block Copolymers in Aqueous Solution and Microemulsions

A nonionic double hydrophilic block copolymer with a long permanently hydrophilic and a small thermoresponsive block is synthesized by reversible addition-fragmentation chain-transfer polymerization (RAFT). By employing a specifically designed chain-transfer agent, the polymer is functionalized with complementary end groups which are suited for Förster resonance energy transfer (FRET). The end group attached to the permanently hydrophilic block of poly(N,N-dimethylacrylamide) pDMAm is designed as a permanently hydrophobic segment ("sticker") comprising a long alkyl chain and the 4-aminonaphthalimide fluorophore. The other end attached to the thermoresponsive block of poly(N-isopropylacrylamide) pNiPAm incorporates a coumarin fluorophore. The temperature-dependent self-assembly of the twofold fluorescently labeled copolymer is studied in pure aqueous solution as well as in an o/w microemulsion by several techniques including turbidimetry, dynamic light scattering (DLS), and fluorescence spectroscopy. It is compared to the behaviors of the analogous twofold-labeled pDMAm and pNiPAm homopolymer references. The findings indicate that the block copolymer behaves as a polymeric surfactant at low temperatures, with one relatively small hydrophobic end block and an extended hydrophilic chain forming "hairy micelles". At elevated temperatures above the LCST phase transition of the pNiPAm block, however, the copolymer behaves as an associative telechelic polymer with two nonsymmetrical hydrophobic end blocks, which do not mix. Thus, instead of a network of bridged "flower micelles", large dynamic aggregates are formed. These are connected alternatingly by the original micellar cores as well as by clusters of the collapsed pNiPAm blocks. This type of structure is even more favored in the o/w microemulsion than in pure aqueous solution, as the microemulsion droplets constitute an attractive anchoring point for the hydrophobic dodecyl sticker but not for the collapsed pNiPAm chains.

Chromophoric Dendrimer-Based Materials: An Overview of Holistic-Integrated Molecular Systems for Fluorescence Resonance Energy Transfer (FRET) Phenomenon

Dendrimers (from the Greek dendros → tree; meros → part) are macromolecules with well-defined three-dimensional and tree-like structures. Remarkably, this hyperbranched architecture is one of the most ubiquitous, prolific, and recognizable natural patterns observed in nature. The rational design and the synthesis of highly functionalized architectures have been motivated by the need to mimic synthetic and natural-light-induced energy processes. Dendrimers offer an attractive material scaffold to generate innovative, technological, and functional materials because they provide a high amount of peripherally functional groups and void nanoreservoirs. Therefore, dendrimers emerge as excellent candidates since they can play a highly relevant role as unimolecular reactors at the nanoscale, acting as versatile and sophisticated entities. In particular, they can play a key role in the properties of light-energy harvesting and non-radiative energy transfer, allowing them to function as a whole unit. Remarkably, it is possible to promote the occurrence of the FRET phenomenon to concentrate the absorbed energy in photoactive centers. Finally, we think an in-depth understanding of this mechanism allows for diverse and prolific technological applications, such as imaging, biomedical therapy, and the conversion and storage of light energy, among others.

FRET Ratiometric Nanoprobes for Nanoparticle Monitoring

Fluorescence labelling is often used for tracking nanoparticles, providing a convenient assay for monitoring nanoparticle drug delivery. However, it is difficult to be quantitative, as many factors affect the fluorescence intensity. Förster resonance energy transfer (FRET), taking advantage of the energy transfer from a donor fluorophore to an acceptor fluorophore, provides a distance ruler to probe NP drug delivery. This article provides a review of different FRET approaches for the ratiometric monitoring of the self-assembly and formation of nanoparticles, their in vivo fate, integrity and drug release. We anticipate that the fundamental understanding gained from these ratiometric studies will offer new insights into the design of new nanoparticles with improved and better-controlled properties.

Detecting and Monitoring Hydrogels with Medical Imaging

Hydrogels, water-swollen polymer networks, are being applied to numerous biomedical applications, such as drug delivery and tissue engineering, due to their potential tunable rheologic properties, injectability into tissues, and encapsulation and release of therapeutics. Despite their promise, it is challenging to assess their properties in vivo and crucial information such as hydrogel retention at the site of administration and in situ degradation kinetics are often lacking. To address this, technologies to evaluate and track hydrogels in vivo with various imaging techniques have been developed in recent years, including hydrogels functionalized with contrast generating material that can be imaged with methods such as X-ray computed tomography (CT), magnetic resonance imaging (MRI), optical imaging, and nuclear imaging systems. In this review, we will discuss emerging approaches to label hydrogels for imaging, review the advantages and limitations of these imaging techniques, and highlight examples where such techniques have been implemented in biomedical applications.

Initial immune response to a FRET-based MMP sensor-immobilized silk fibroin hydrogel in vivo

To investigate the initial immune response to biodegradable silk fibroin (SF) hydrogels in vivo, a Förster/fluorescence resonance energy transfer (FRET)-based sensor was developed to detect matrix metalloproteinase (MMP) activity (FRET-MMPS) and immobilized to SF hydrogel. FRET-MMPS immobilized to SF hydrogel in vitro displayed intra-molecular FRET more than inter-molecular FRET, and MMP activity was detected through a decrease in FRET signal intensity. Then, the SF hydrogel modified with FRET-MMPS was implanted into mice subcutaneously, and it was observed that the FRET signal intensity decreased significantly soon (< 3 h) after implantation. Although the intensity exhibited a sharp decrease toward 24 h post-implantation, histological evaluation proved that bulk-level hydrogel degradation, such as breakdown, was mainly caused by macrophages and foreign body giant cells on a timescale of weeks. These results indicated that, immediately upon implantation, active MMPs reached the SF hydrogel and began cleaving SF networks, which might result in the loosening of the networks and then enabled immune cells, such as macrophages, to start the bulk-level hydrogel degradation. The sensor clarified the initial immune response to SF hydrogels and will provide clues for designing the biodegradation behaviors of scaffolds for regenerative medicine. STATEMENT OF SIGNIFICANCE: Silk fibroin (SF) materials are degraded gradually by the immune response. Immune cells, such as macrophages, break down implanted SF materials on a timescale of weeks or months, but the initial (< 24 h) immune response to SF materials remains unclear. In this study, SF hydrogels modified with Förster/fluorescence resonance energy transfer (FRET)-based matrix metalloproteinase (MMP) sensors were implanted in mice and within 3 h post-implantation, the SF hydrogels were degraded by MMPs. Although this molecular-level biodegradation was not correlated with the hydrogel breakdown, the MMPs were likely to loosen the SF networks to enable immune cells to infiltrate and degrade the hydrogel. This is the first study to unveil the initial stage of immune response to biomaterials.

Thermo-Responsive Hydrogels: From Recent Progress to Biomedical Applications

Thermogels are also known as thermo-sensitive or thermo-responsive hydrogels and can undergo a sol-gel transition as the temperature increases. This thermogelling behavior is the result of combined action from multiscale thermo-responsive mechanisms. From micro to macro, these mechanisms can be attributed to LCST behavior, micellization, and micelle aggregation of thermogelling polymers. Due to its facile phase conversion properties, thermogels are injectable yet can form an in situ gel in the human body. Thermogels act as a useful platform biomaterial that operates at physiological body temperatures. The purpose of this review is to summarize the recent progress in thermogel research, including investigations on the thermogel gelation mechanism and its applications in drug delivery, 3D cell culture, and tissue engineering. The review also discusses emerging directions in the study of thermogels.

Cancer theranostic platforms based on injectable polymer hydrogels

Theranostic platforms that combine therapy with diagnosis not only prevent the undesirable biological responses that may occur when these processes are conducted separately, but also allow individualized therapies for patients. Polymer hydrogels have been employed to provide well-controlled drug release and targeted therapy in theranostics, where injectable hydrogels enable non-invasive treatment and monitoring with a single injection, offering greater patient comfort and efficient therapy. Efforts have been focused on applying injectable polymer hydrogels in theranostic research and clinical use. This review highlights recent progress in the design of injectable polymer hydrogels for cancer theranostics, particularly focusing on the elements/components of theranostic hydrogels, and their cross-linking strategies, structures, and performance with regard to drug delivery/tracking. Therapeutic agents and tracking modalities that are essential components of the theranostic platforms are introduced, and the design strategies, properties and applications of the injectable hydrogels developed via two approaches, namely chemical bonds and physical interactions, are described. The theranostic functions of the platforms are highly dependent on the architecture and components employed for the construction of hydrogels. Challenges currently presented by theranostic platforms based on injectable hydrogels are identified, and prospects of acquiring more comfortable and personalized therapies are proposed.

Supramolecular co-assembly of self-adjuvanting nanofibrious peptide hydrogel enhances cancer vaccination by activating MyD88-dependent NF-κB signaling pathway without inflammation

Peptide vaccine targeting tumor-specific antigens is a promising cancer treatment regimen. However, peptide vaccines are commonly low-immunogenic, leading to suboptimal antitumor T-cell responses. Current peptide vaccination approaches are challenged by the variability of peptide physicochemical characters and vaccine formulations, flexibility, and the broad feasibility. Here, the supramolecular co-assembly of antigen epitope-conjugated peptides (ECPs) targeting CD8 or CD4 T-cell receptors was used to engineer a nanofibrious hydrogel vaccine platform. This approach provided precise and tunable loading of peptide antigens in nanofibers, which notably increased the antigen uptake, cross-presentation, and activation of dendritic cells (DCs). Immunization in mice indicated that the co-assembled peptide hydrogel did not induce local inflammation responses and elicited significantly promoted T-cell immunity by activating the MyD88-dependent NF-κB signaling pathway in DCs. Vaccination of mice using co-assembled peptide vaccine stimulated both enhanced CD8 and CD4 T cells against EG.7-OVA tumors without additional immunoadjuvants or delivery systems, and resulted in a more remarkable cancer immunotherapy efficacy, compared with free peptide vaccine or aluminum-adjuvanted peptide formulation. Altogether, peptide co-assembly demonstrated by three independent pairs of ECPs is a facile, customizable, and chemically defined approach for co-delivering peptide antigens in self-adjuvanting hydrogel vaccines that could induce stronger anticancer T-cell responses.

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Supramolecular co-assembly is a facile approach for manufacturing peptide vaccine.

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Peptide vaccine activates DCs through the MyD88-dependent NF-κB signaling pathway.

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Vaccination of co-assembled peptide hydrogel augments antitumor T-cell responses.

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Co-assembled peptide vaccine shows therapeutic cancer immunotherapy efficacy.

Capturing the Real-Time Hydrolytic Degradation of a Library of Biomedical Polymers by Combining Traditional Assessment and Electrochemical Sensors

We have developed an innovative methodology to overcome the lack of techniques for real-time assessment of degradable biomedical polymers at physiological conditions. The methodology was established by combining polymer characterization techniques with electrochemical sensors. The in vitro hydrolytic degradation of a series of aliphatic polyesters was evaluated by following the molar mass decrease and the mass loss at different incubation times while tracing pH and l-lactate released into the incubation media with customized miniaturized electrochemical sensors. The combination of different analytical approaches provided new insights into the mechanistic and kinetics aspects of the degradation of these biomedical materials. Although molar mass had to reach threshold values for soluble oligomers to be formed and specimens' resorption to occur, the pH variation and l-lactate concentration were direct evidence of the resorption of the polymers and indicative of the extent of chain scission. Linear models were found for pH and released l-lactate as a function of mass loss for the l-lactide-based copolymers. The methodology should enable the sequential screening of degradable polymers at physiological conditions and has potential to be used for preclinical material's evaluation aiming at reducing animal tests.

Synthetic Polymeric Antibacterial Hydrogel for Methicillin-Resistant Staphylococcus aureus-Infected Wound Healing: Nanoantimicrobial Self-Assembly, Drug- and Cytokine-Free Strategy

Antibacterial hydrogels are attracting extensive attention in soft tissue repair and regeneration, including bacteria-infected-wound healing. The abuse of antibiotics leads to drug resistance. Recent developments have demonstrated that the delivery of inorganic bactericidal agents in hydrogels can drive the wound healing process; however, this approach is complicated by external light stimuli, cytotoxicity, nondegradability, and sophisticated fabrication. Herein, an inherent antibacterial, bioresorbable hydrogel was developed by the spontaneous self-aggregation of amphiphilic, oxadiazole-group-decorated quaternary ammonium salts (QAS)-conjugated poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCEC-QAS) micellar nanoantimicrobials for methicillin-resistant Staphylococcus aureus (MRSA)-infected cutaneous wound healing. The PCEC-QAS hydrogel showed a stable gel state within the temperature range of 5-50 °C and antibacterial efficacy against both Gram-negative and -positive bacteria in vitro and in vivo. Additionally, the PCEC-QAS hydrogel facilitated the cell spreading, proliferation, and migration without cytotoxicity. An in vivo degradation and skin defect healing study suggested the PCEC-QAS hydrogel was totally absorbed without local or systemic toxicity and could promote wound repair in the absence of drugs, cytokines, or cells. Significantly, this hydrogel accelerated the regeneration of a MRSA-infected full-thickness impaired skin wound by successfully reconstructing an intact and thick epidermis similar to normal mouse skin. Collectively, a self-assembling PCEC-QAS antibacterial hydrogel is a promising dressing material to promote skin regeneration and prevent bacterial infection without additional drugs, cells, light irradiation, or delivery systems, providing a simple but effective strategy for treating dermal wounds.

Development of injectable thermosensitive polypeptide hydrogel as facile radioisotope and radiosensitizer hotspot for synergistic brachytherapy

Brachytherapy is considered to be an unparalleled form of conformal radiation therapy, which involves the delivery of radiation directly to tumor lesions or the postoperative cavity. With the development of specific applicators, the exploitation of in situ drug-delivery platform introduces opportunities for the synchronous administration of radiosensitizers. In this study, an iodine-131 (I¹³¹)-labeled injectable thermosensitive methoxy poly(ethylene glycol)-b-poly(tyrosine) hydrogel (denoted as PETyr-I¹³¹) was developed via a facile method. The radioactive source of I¹³¹ was immobilized at the subcutaneous injection site and monitored via single-photon emission computed tomography in real time, and hematological and histopathological analyses revealed no obvious side effects. Additionally, the SmacN7 peptide conjugated with cell membrane-permeable oligosarginine (denoted as SmacN7-R9) was used to enhance the radiosensitivity of cancer cells, as confirmed by the results of reactive oxygen species detection, DNA damage assay, cell apoptosis assay, and clonogenic evaluation. Importantly, a synergistic brachytherapy treatment effect on tumor-bearing nude mice was achieved. The proposed thermosensitive supramolecular hydrogel platform, which conformally immobilizes radionuclides and delivers radiosensitizers by virtue of its proximity to the site of the primary tumor or the postoperative cavity, has great potential for achieving synergistic treatment outcomes with reduced radiation-related side effects. STATEMENT OF SIGNIFICANCE: In this work, a kind of radioiodinated thermosensitive supramolecular hydrogel was developed, which was facilely used as the radioactive source for brachytherapy. Meanwhile, SmacN7-R9 peptide was combined as a model radiosensitizer to facilitate the activation of tumor cell apoptosis pathways and promotion of radiation-induced cytotoxicity. Synergistic brachytherapy outcomes were achieved from the in vitro and in vivo evaluations. Therefore, from the practical standpoint, this thermosensitive supramolecular hydrogel platform holds great potential for the 3D-conformally immobilizing radionuclide and delivering radiosensitizer by virtue of its proximity to the site of primary tumor lesions or postoperative cavity, resulting in synergetic treatment outcomes with reduced radiation associated side effects.

Black phosphorus nanosheets and docetaxel micelles co-incorporated thermoreversible hydrogel for combination chemo-photodynamic therapy

The platform of the combination chemo-photodynamic therapy has received widespread attention for enhancing anticancer efficacy and inhibiting tumor growth, which supports thermosensitive and controlled drug release. Here, an injectable thermoreversible hydrogel (BPNSs/DTX-M-hydrogel) co-encapsulating black phosphorus nanosheets (BPNSs) and docetaxel (DTX) micelles was prepared to increase drug accumulation in tumor tissue and improve anticancer efficacy. BPNSs were prepared by liquid exfoliation method with a simple and rapid preparation, and DTX micelles were prepared by the thin film dispersion method. Hydrogel was prepared with F127 as hydrogel matrix for intratumoral injection. BPNSs, DTX micelles, and BPNSs/DTX-M-hydrogel were characterized by particle size, morphology, stability and degradation, phase transition feature, and photodynamic performance. And the in vivo anticancer efficacy was evaluated in 4T1 tumor-bearing Balb/c mice. The results showed that the particle size of DTX micelles and BPNSs were about 16 and 180 nm, respectively. The hydrogel with the transformation temperature at near body exhibited great photodynamic efficacy and good biodegradability. Moreover, BPNSs/DTX-M-hydrogel with the combination of chemotherapy and photodynamic therapy exhibited unique anticancer efficacy with low toxicity. In conclusion, the combination platform of chemo-photodynamic therapy based on BPNSs could be a prospective strategy in antitumor research. Graphical abstract.

Injectable DNA-architected nanoraspberry depot-mediated on-demand programmable refilling and release drug delivery

Drug delivery depots boosting a local concentration of therapeutic agents have received great attention in clinical applications due to their low occurrence of side effects and high therapeutic efficacy. However, once the payload is exhausted, the local drug concentration will be lower than the therapeutic window. To address this issue, an injectable double-strand deoxyribonucleic acid (DNA)-architected nanoraspberry depot (DNR-depot) was developed that can refill doxorubicin (Dox, an anticancer drug) from the blood and remotely control drug release on demand. The large porous surface on a uniform nanoraspberry (NR) filled covalently with DNA serves as a Dox sponge-like refilling reservoir, and the NR serves as a magnetic electrical absorber. Via the strong affinity between Dox and DNA molecules, the refilling process of Dox can be achieved on DNR-depot both in vitro and in vivo. Upon high-frequency magnetic field (HFMF) treatment, the remotely triggered release of Dox is actuated by the dissociation of Dox and DNA molecules, facilitating an approximately 800% improvement in drug concentration at the tumor site compared to free Dox injection alone. Furthermore, the cycles of refilling and release can be carried out more than 3 times in vivo within 21 days. The combination of refilling and HFMF-programmable Dox release in tumors via DNR-depot can effectively inhibit tumor growth for 30 days.

19F magnetic resonance imaging enabled real-time, non-invasive and precise localization and quantification of the degradation rate of hydrogel scaffolds in vivo

The degradation behavior of hydrogel scaffolds is closely related to the controlled release of bioactive agents and matching with the proliferative demands of newly generated tissues. However, the current methods cannot provide precise localization and track the degradation of individual hydrogel scaffolds in vivo, despite superficial or volumetric information. Here, for the first time, we presented the use of ¹⁹F magnetic resonance imaging (¹⁹F MRI) to precisely monitor the localization and quantify the degradation rate of implantable or injectable hydrogels in a real-time and noninvasive manner, with no interference of endogenous background signals and limitation of penetration depth. The total voxel and content in the region of interest (ROI) were linearly correlated to the injection amount, providing exact three-dimensional (3D) stereoscopic and two-dimensional (2D) anatomical information in the meantime. Moreover, a computational algorithm was established to present the real-time degradation rate in vivo as a function of time, which was implemented directly from the ¹⁹F MRI dataset. In addition, labelling with a zwitterionic ¹⁹F contrast agent demonstrated a facile and general applicability for multiple types of materials with no influence on their original gelation properties as well as ¹⁹F NMR properties in the hydrogel matrix. Therefore, this ¹⁹F MRI method offers a new approach to non-invasively track the degradation rate of hydrogel scaffolds in vivo in a precise localization and accurate quantification way, which will suffice the need for the evaluation of implants at deep depths in large animals or human objects.

An aggregation-induced emission dye-powered afterglow luminogen for tumor imaging

Semiconducting polymer (SP)-based afterglow luminogens are showing increasing potential for in vivo imaging because of their long-life luminescence and the associated benefits (e.g., zero-autofluorescence background and high signal-to-noise ratio). However, such organic afterglow luminescence agents are still rare and their application is usually limited by their relatively low afterglow intensity and short afterglow duration. Herein, we report an aggregation-induced emission (AIE) dye-powered SP afterglow luminogen by leveraging on the unique characteristics of an AIE dye to circumvent the concentration-quenching effect, enhance afterglow intensity and prolong afterglow duration. The underlying working mechanism is investigated by a series of experiments and it is found that the AIE dye provides sufficient 1O2 to excite SPs and form massive amounts of high-energy intermediates, and then the SP intermediates emit photons that can activate the AIE dye to generate 1O2 and simultaneously trigger the energy transfer process between the SPs and AIE dye, resulting in a deep-red emission. It is this closed-loop of "photon-1O2-SP intermediates-photon" that provides the afterglow emission even after the cessation of the excitation light. The as-prepared luminogen shows good performance in in vivo tumour imaging. This study demonstrates the advantages of AIE-facilitated afterglow luminescence and discloses its mechanism, and hopefully it could inspire the development of other innovative designs for cancer theranostics.

Supramolecular thermogels from branched PCL-containing polyurethanes

Thermogels are temperature-responsive hydrogels which are most commonly formed by supramolecular self-assembly of polymer amphiphiles comprising of both hydrophobic and hydrophilic segments. Although polyurethane thermogels have shown great promise as biomaterials, their synthesis by step-growth polymerisation of diols and diisocyanates can also result in formation of allophanate branches, which arise from the reaction between free isocyanate groups and urethane linkages along the polymer backbone. In this paper, we investigate the effects of different synthetic conditions on the degree of allophanate branching on polyurethane amphiphiles, and explore the influences of these branches on the polymers' critical micelle concentration (CMC), thermodynamics of micellization and subsequent thermogel properties. Our findings offer new insights into the relationship between polymer structure, micelle and gel properties. These results highlight the importance of taking polymer branching into account for understanding the hierarchical self-assembly of polymer amphiphiles and the resulting thermogel properties and behaviour.

Polymer branching exerts notable influence on the spontaneous temperature-triggered self-assembly of amphiphilic polymers into micelles and thermogels in water.

Application of Förster Resonance Energy Transfer (FRET) technique to elucidate intracellular and In Vivo biofate of nanomedicines

Extensive studies on nanomedicines have been conducted for drug delivery and disease diagnosis (especially for cancer therapy). However, the intracellular and in vivo biofate of nanomedicines, which is significantly associated with their clinical therapeutic effect, is poorly understood at present. This is because of the technical challenges to quantify the disassembly and behaviour of nanomedicines. As a fluorescence- and distance-based approach, the Förster Resonance Energy Transfer (FRET) technique is very successful to study the interaction of nanomedicines with biological systems. In this review, principles on how to select a FRET pair and construct FRET-based nanomedicines have been described first, followed by their application to study structural integrity, biodistribution, disassembly kinetics, and elimination of nanomedicines at intracellular and in vivo levels, especially with drug nanocarriers including polymeric micelles, polymeric nanoparticles, and lipid-based nanoparticles. FRET is a powerful tool to reveal changes and interaction of nanoparticles after delivery, which will be very useful to guide future developments of nanomedicine.

Enhanced photo/chemo combination efficiency against bladder tumor by encapsulation of DOX and ZnPC into in situ-formed thermosensitive polymer hydrogel

BACKGROUND

Chemotherapy after transurethral resection is commonly recommended for bladder cancer. However, studies have shown that chemotherapy solely can hardly decrease progression rates of bladder cancer. The combination of chemotherapeutic agents with photo-dynamic therapy (PDT), a new promising localized therapy, may become a workable strategy for combating bladder cancer. This study reports the combination of doxorubicin (DOX)-based chemotherapy and zinc phthalocyanine (ZnPC)-based PDT using in situ-formed thermal-responsive copolymer hydrogel.

MATERIALS AND METHODS

The copolymer was synthesized by polymerization of 3-caprolactone, 1,4,8-trioxa[4.6]spiro-9-undecanone and poly(ethylene glycol) and was abbreviated as PCL-PTSUO-PEG. The thermal-responsive nanoparticles (TNPs) were prepared by the nanoprecipitation technology. The thermal-responsive hydrogel was formed after 37°C heating of TNP solution. The size, morphology and dynamic viscosity of hydrogel were detected. The in vitro drug release profile of TNP/DOX/ZnPC was performed. Cell uptake, cell inhibition and ROS generation of TNP/DOX/ZnPC were studied in 5637 cells. The in vivo antitumor activity of TNP/DOX/ZnPC was evaluated in nude mice bearing 5637 cells xenograft.

RESULTS

TNP/DOX and TNP/ZnPC had an average diameter of 102 and 108 nm, respectively. After being heated at 37°C for 5 minutes, TNP/DOX and TNP/ZnPC solution turned uniform light red and dark green hydrogel. ZnPC encapsulation designed by TNP could significantly improve its aqueous solubility to 1.9 mg/mL. Cell inhibition showed that the best cell inhibition was found, with cell viability of 18.5%, when the weight ratio of DOX and ZnPC encapsulated in the TNP reached about 1:5. TNP/DOX/ZnPC generated relative high level of ROS with 4.8-fold of free ZnPC and 1.6-fold of TNP/ZnPC. TNP/DOX/ZnPC showed only 8-fold of relative tumor growth without obvious toxicity to the mice.

CONCLUSION

Thermosensitive thermal-responsive hydrogel reported in this contribution are promising in situ-formed matrix for DOX- and ZnPC-based photo/chemo combination treatment for bladder cancer therapy.

Thermo-Sensitive Nanomaterials: Recent Advance in Synthesis and Biomedical Applications

Progress in nanotechnology has enabled us to open many new fronts in biomedical research by exploiting the peculiar properties of materials at the nanoscale. The thermal sensitivity of certain materials is a highly valuable property because it can be exploited in many promising applications, such as thermo-sensitive drug or gene delivery systems, thermotherapy, thermal biosensors, imaging, and diagnosis. This review focuses on recent advances in thermo-sensitive nanomaterials of interest in biomedical applications. We provide an overview of the different kinds of thermoresponsive nanomaterials, discussing their potential and the physical mechanisms behind their thermal response. We thoroughly review their applications in biomedicine and finally discuss the current challenges and future perspectives of thermal therapies.

l-Peptide functionalized dual-responsive nanoparticles for controlled paclitaxel release and enhanced apoptosis in breast cancer cells

Nanoparticles and macromolecular carriers have been widely used to increase the efficacy of chemotherapeutics, largely through passive accumulation provided by their enhanced permeability and retention effect. However, the therapeutic efficacy of nanoscale anticancer drug delivery systems is severely truncated by their low tumor-targetability and inefficient drug release at the target site. Here, the design and development of novel l-peptide functionalized dual-responsive nanoparticles (l-CS-g-PNIPAM-PTX) for active targeting and effective treatment of GRP78-overexpressing human breast cancer in vitro and in vivo are reported. l-CS-g-PNIPAM-PTX NPs have a relative high drug loading (13.5%) and excellent encapsulation efficiency (74.3%) and an average diameter of 275 nm. The release of PTX is slow at pH 7.4 and 25 °C but greatly accelerated at pH 5.0 and 37 °C. MTT assays and confocal experiments showed that the l-CS-g-PNIPAM-PTX NPs possessed high targetability and antitumor activity toward GRP78 overexpressing MDA-MB-231 human breast cancer cells. As expected, l-CS-g-PNIPAM-PTX NPs could effectively treat mice bearing MDA-MB-231 human breast tumor xenografts with little side effects, resulting in complete inhibition of tumor growth and a high survival rate over an experimental period of 60 days. These results indicate that l-peptide-functionalized acid - and thermally activated - PTX prodrug NPs have a great potential for targeted chemotherapy in breast cancer.