Control of hyperbranched structure of polycaprolactone/poly(ethylene glycol) polyurethane block copolymers by glycerol and their hydrogels for potential cell delivery

From nano to the macro: tuning hierarchical aggregation of thermoresponsive PEG/PCL-based polyurethanes via molar mass/composition control

Amphiphilic hyperbranched polyurethanes (HPUs) based on PEG and PCL are promising for several biomedical applications. However, the lack of control over the molar mass and composition hinders a deep understanding of the aqueous self-assembly of HPUs. In this paper, the control over the HPU molar mass and composition was provided by dynamic urea bond-mediated polymerization (DUBMP), enabling a careful evaluation of their aqueous self-assembly by 1H NMR, DLS, and Cryo-TEM. HPUs containing a single PCL block per chain self-assemble into nanoaggregates (Rh ≈ 10 nm) in water up to its cloud-point temperature (Tcp) of 34 °C. On the other hand, HPUs with more than one PCL block per chain self-assemble into nanoaggregates and their clusters below Tcp. In this case, the solution behavior can be tuned by the HPU molar mass. Increasing $$\overline{{\mathrm{M} }_{\mathrm{w}}}$$ M w ¯ from 4 to 19 kDa, HPUs of similar composition can form colloidally stable cluster suspensions ($$\overline{{\mathrm{M} }_{\mathrm{w}}}$$ M w ¯ = 4 kDa) and phase separate into a denser liquid aggregate–cluster phase ($$\overline{{\mathrm{M} }_{\mathrm{w}}}$$ M w ¯ = 7 kDa) or into a highly viscous aggregate-network phase ($$\overline{{\mathrm{M} }_{\mathrm{w}}}$$ M w ¯ = 19 kDa). This type of control over the hierarchical aggregation of HPUs was reported for the first time and is interesting for biomedical applications.

Graphical abstract

Facile Construction of a Two-in-One Injectable Micelleplex-Loaded Thermogel System for the Prolonged Delivery of Plasmid DNA

Nanoparticle-hydrogel systems have recently emerged as a class of interesting hybrid materials with immense potential for several biomedical applications. Remarkably, the incorporation of nanoparticles into a hydrogel may yield synergistic benefits lacking in a singular system. However, most synthetic strategies require laborious steps to achieve the system, severely restricting the process of translational research. Herein, a facile strategy to access a two-in-one system comprising two distinct polyurethane (PU)-based micellar systems is demonstrated and applied as a novel sustained gene delivery platform, where the two PUs are synthesized similarly but with slightly different compositions. One PU forms cationic micelles that complex with plasmid DNA (pDNA), which are loaded into a thermogel formed by another PU micellar system for the prolonged release of pDNA micelleplexes. Specifically, a thermogelling multiblock PU copolymer (denoted as EPH) was synthesized via the step-growth polymerization of poly(ethylene glycol), poly(propylene glycol), and poly(3-hydroxybutyrate). By further introducing a cationic extender, 3-(dimethylamino)-1,2-propanediol, into the reaction feed, a series of cationic PUs (denoted as EPHD) with varying compositions were obtained. The EPHDs formed positively charged micelles in aqueous solutions, efficiently condensed pDNA into nano-sized micelleplexes (<200 nm) at optimized w/w ratios, and mediated transient green fluorescence protein expression in HEK293T cells at 48 h post-transfection. On the other hand, aqueous EPH solution (4 wt %) was injectable at 4 °C and rapidly gelled upon heating to 37 °C to form a stable hydrogel depot. EPHD/pDNA micelleplexes were easily loaded into EPH by mixing the solutions at 4 °C, before heating to 37 °C, leading to the resultant hydrogel system. The in vitro release study revealed that while free pDNA loaded in the thermogel was completely released in 2 weeks, the release of EPHD/pDNA micelleplexes was prolonged to at least 28 days, suggesting substantial micelleplex-hydrogel interactions. Intact, bioactive, and noncytotoxic EPHD/pDNA micelleplexes in the release media were proved by gel retardation, in vitro gene transfection, and CCK-8 cytotoxicity assay results, respectively. Collectively, this work presents a simple approach to achieving and optimizing a novel two-in-one nanoparticle-hydrogel system for the prolonged delivery of pDNA and may be promising for long-term gene delivery applications.

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.

Hyperbranched polymer hydrogels with large stimuli-responsive changes in storage moduli and peroxide-induced healing

Hydrogels prepared using hyperbranched polymers with dynamic disulfide bonds show larger changes in moduli upon exposure to chemical stimuli for both softening and stiffening responses compared to linear polymers.

Composite Hydrogel of Methacrylated Hyaluronic Acid and Fragmented Polycaprolactone Nanofiber for Osteogenic Differentiation of Adipose-Derived Stem Cells

Composite hydrogels with electrospun nanofibers (NFs) have recently been used to mimic the native extracellular matrix. In this study, composite hydrogels of methacrylated hyaluronic acid containing fragmented polycaprolactone NFs were used for bone tissue engineering. The composite (NF/hydrogel) was crosslinked under ultraviolet (UV) light. The incorporation of fragmented polycaprolactone NFs increased the compression modulus from 1762.5 to 3122.5 Pa. Subsequently, adipose-derived stem cells incorporated into the composite hydrogel exhibited a more stretched and elongated morphology and osteogenic differentiation in the absence of external factors. The mRNA expressions of osteogenic biomarkers, including collagen 1 (Col1), alkaline phosphatase, and runt-related transcription factor 2, were 3-5-fold higher in the composite hydrogel than in the hydrogel alone. In addition, results of the protein expression of Col1 and alizarin red staining confirmed osteogenic differentiation. These findings suggest that our composite hydrogel provides a suitable microenvironment for bone tissue engineering.

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.

A one-pot, solvent-free, and controlled synthetic route for thermoresponsive hyperbranched polyurethanes

Hyperbranched polyurethanes (HPUs) are known for their multifunctionality and versatile properties.

Hydrogel scaffolds for tissue engineering: the importance of polymer choice

We explore the design and synthesis of hydrogel scaffolds for tissue engineering from the perspective of the underlying polymer chemistry. The key polymers, properties and architectures used, and their effect on tissue growth are discussed.

Additive Manufacturing of Personalized Pharmaceutical Dosage Forms via Stereolithography

The introduction of three-dimensional printing (3DP) has created exciting possibilities for the fabrication of dosage forms, paving the way for personalized medicine. In this study, oral dosage forms of two drug concentrations, namely 2.50% and 5.00%, were fabricated via stereolithography (SLA) using a novel photopolymerizable resin formulation based on a monomer mixture that, to date, has not been reported in the literature, with paracetamol and aspirin selected as model drugs. In order to produce the dosage forms, the ratio of poly(ethylene glycol) diacrylate (PEGDA) to poly(caprolactone) triol was varied with diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure TPO) utilized as the photoinitiator. The fabrication of 28 dosages in one print process was possible and the printed dosage forms were characterized for their drug release properties. It was established that both drugs displayed a sustained release over a 24-h period. The physical properties were also investigated, illustrating that SLA affords accurate printing of dosages with some statistically significant differences observed from the targeted dimensional range, indicating an area for future process improvement. The work presented in this paper demonstrates that SLA has the ability to produce small, individualized batches which may be tailored to meet patients’ specific needs or provide for the localized production of pharmaceutical dosage forms.

PCL-Based Composite Scaffold Matrices for Tissue Engineering Applications

Biomaterial-based scaffolds are important cues in tissue engineering (TE) applications. Recent advances in TE have led to the development of suitable scaffold architecture for various tissue defects. In this narrative review on polycaprolactone (PCL), we have discussed in detail about the synthesis of PCL, various properties and most recent advances of using PCL and PCL blended with either natural or synthetic polymers and ceramic materials for TE applications. Further, various forms of PCL scaffolds such as porous, films and fibrous have been discussed along with the stem cells and their sources employed in various tissue repair strategies. Overall, the present review affords an insight into the properties and applications of PCL in various tissue engineering applications.

Using Artificial Skin Devices as Skin Replacements: Insights into Superficial Treatment

Artificial skin devices are able to mimic the flexibility and sensory perception abilities of the skin. They have thus garnered attention in the biomedical field as potential skin replacements. This Review delves into issues pertaining to these skin-deep devices. It first elaborates on the roles that these devices have to fulfill as skin replacements, and identify strategies that are used to achieve such functionality. Following which, a comparison is done between the current state of these skin-deep devices and that of natural skin. Finally, an outlook on artificial skin devices is presented, which discusses how complementary technologies can create skin enhancements, and what challenges face such devices.

Polyester elastomers for soft tissue engineering

Polyester elastomers are soft, biodegradable and biocompatible and are commonly used in various biomedical applications, especially in tissue engineering. These synthetic polyesters can be easily fabricated using various techniques such as solvent casting, particle leaching, molding, electrospinning, 3-dimensional printing, photolithography, microablation etc. A large proportion of tissue engineering research efforts have focused on the use of allografts, decellularized animal scaffolds or other biological materials as scaffolds, but they face the major concern of triggering immunological responses from the host, on top of other issues. This review paper will introduce the recent developments in elastomeric polyesters, their synthesis and fabrication techniques, as well as their application in the biomedical field, focusing primarily on tissue engineering in ophthalmology, cardiac and vascular systems. Some of the commercial and near-commercial polyesters used in these tissue engineering fields will also be described.

A Recent Perspective on Noncovalently Formed Polymeric Hydrogels

Chemically crosslinked covalent hydrogels form a permanent and often strong network, and have been extensively used so far in drug delivery and tissue engineering. However, it is more difficult to induce dynamic and highly tunable changes in these hydrogels. Noncovalently formed hydrogels show promise as inherently reversible systems with an ability to change in response to dynamic environments, and have garnered strong interest recently. In this Personal Account, we elucidate a few key attractive properties of noncovalent hydrogels and describe recent developments in hydrogels crosslinked using various different noncovalent interactions. These hydrogels offer huge control for modulating material properties and could be more relevant mimics for biological systems.

Hierarchically Self-Assembled Supramolecular Host-Guest Delivery System for Drug Resistant Cancer Therapy

In this report, a new star-like copolymer β-CD- g-(PNIPAAm- b-POEGA) _x, consisting of a β-CD core, grafted with temperature-responsive poly( N-isopropylacrylamide) (PNIPAAm) and biocompatible poly(oligo(ethylene glycol) acrylate) (POEGA) in a block copolymer of the arms, was used to deliver chemotherapeutics to drug resistant cancer cells and tumors. The first step of the self-assembly process involves the encapsulation of chemotherapeutics through host-guest inclusion complexation between the β-cyclodextrin cavity and the anticancer drug. Next, the chain interaction of the PNIPAAm segment at elevated temperature drives the drug-loaded β-CD- g-(PNIPAAm- b-POEGA) _x/PTX inclusion complex to hierarchically self-assemble into nanosized supramolecular assemblies at 37 °C, whereas the presence of poly(ethylene glycol) (PEG) chains in the distal end of the star-like copolymer arms impart enhanced stability to the self-assembled structure. More interestingly, this supramolecular host-guest nanocomplex promoted the enhanced cellular uptake of chemotherapeutics in MDR-1 up-regulated drug resistant cancer cells and exhibited high therapeutic efficacy for suppressing drug resistant tumor growth in an in vivo mouse model, due to the increased stability, improvement in aqueous solubility, enhanced cellular uptake, and partial membrane pump impairment by taking the advantage of PEGylation and supramolecular complex between this star-like copolymer and chemotherapeutics. This work signifies that temperature-sensitive PEGylated supramolecular nanocarriers with good biocompatibility are effective in combating MDR-1 mediated drug resistance in both in vitro and in vivo models, which is of significant importance for the advanced drug delivery platform designed to combat drug resistant cancer.

Poly(carbonate urethane)-Based Thermogels with Enhanced Drug Release Efficacy for Chemotherapeutic Applications

In this study, we report the synthesis and characterisation of a thermogelling poly(carbonate urethane) system comprising poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG) and poly(polytetrahydrofuran carbonate) (PTHF carbonate). The incorporation of PTHF carbonate allowed for the control of the lower critical solution temperature (LCST) and decreased critical gelation concentration (CGC) of the thermogels significantly. In addition, the as-prepared thermogels displayed low toxicity against HepG2, L02 and HEK293T cells. Drug release studies were carried out using doxorubicin (Dox). Studies conducted using nude mice models with hepatocellular carcinoma revealed that the Dox-loaded poly(PEG/PPG/PTHF carbonate urethane) thermogels showed excellent in vivo anti-tumour performance and effectively inhibited tumour growth in the tested model.

Recent advances in the development of biodegradable PHB-based toughening materials: Approaches, advantages and applications

Polyhydroxybutyrate (PHB) is a natural biodegradable polymer that is produced by many types of bacteria as an intracellular energy storage material. Due to its numerous advantages such as biodegradability, biocompatibility, availability and with physical properties comparable to petroleum-based thermoplastics, PHB is a potential substitute in biomedical and packaging fields. However, several physical drawbacks, such as high production cost, thermal instability, and poor mechanical properties, due to secondary crystallization and slow nucleation rate, limit its competition with traditional plastics in industrial and biomedical applications. Thereby, many attempts have been employed to improve the material performance of toughened PHB so as to achieve greater competitiveness and sustainability. In this review, the most recent developments of PHB-based toughening materials are discussed with respect to their approaches and strategies, which includes: drawing and thermal treatment, blending with materials from natural sources and synthetic polymers, as well as forming reinforced composites with natural fibers and inorganic fillers. The alternation of PHB chemical structure to form various types of functional copolymers with enhanced materials performance is also summarized. The expanded utilization of these newly developed sophisticated PHB materials as engineering materials and the biomedical significance in different domains are also addressed.

A review of recent progress in drug and protein encapsulation: Approaches, applications and challenges

Many drugs and proteins formulated for treatment of various diseases are not fully utilised due to environmentally problems such as degradation by enzymes or it being hydrophobic. To counter this problem, the drug and protein of interest are encapsulated by synthetic polymers where they are protected from the environment. This allows the molecule to reach its target safely and maximise its function. In this paper, we will discuss about the different techniques of encapsulation that includes emulsion evaporation, self-emulsifying drug delivery system and supercritical fluid. This will be followed by the drugs and proteins that are commonly encapsulated to counter life-threatening diseases such as cancer and diabetes. A novel method using foam was proposed and will be briefly discussed as it can play a huge role in future developments.

Nano-Star-Shaped Polymers for Drug Delivery Applications

With the advancement of polymer engineering, complex star-shaped polymer architectures can be synthesized with ease, bringing about a host of unique properties and applications. The polymer arms can be functionalized with different chemical groups to fine-tune the response behavior or be endowed with targeting ligands or stimuli responsive moieties to control its physicochemical behavior and self-organization in solution. Rheological properties of these solutions can be modulated, which also facilitates the control of the diffusion of the drug from these star-based nanocarriers. However, these star-shaped polymers designed for drug delivery are still in a very early stage of development. Due to the sheer diversity of macromolecules that can take on the star architectures and the various combinations of functional groups that can be cross-linked together, there remain many structure-property relationships which have yet to be fully established. This review aims to provide an introductory perspective on the basic synthetic methods of star-shaped polymers, the properties which can be controlled by the unique architecture, and also recent advances in drug delivery applications related to these star candidates.

Recent development of synthetic nonviral systems for sustained gene delivery

Sustained gene delivery is of particular importance today because it circumvents the need for repeated therapeutic administration and provides spatial and temporal control of the release profile. Better understanding of the genetic basis of diseases and advances in gene therapy have propelled significant research on biocompatible gene carriers for therapeutic purposes. Varied biodegradable polymer-based architectures have been used to create new compositions with unique properties suitable for sustained gene delivery. This review presents the most recent advances in various polymeric systems: hydrogels, microspheres, nanospheres and scaffolds, having complex architectures to encapsulate and deliver functional genes. Through the recombination of different existing polymer systems, the multicomplex systems can be further endowed with new properties for better-targeted biomedical applications.

“Y”-shape armed amphiphilic star-like copolymers: design, synthesis and dual-responsive unimolecular micelle formation for controlled drug delivery

Dual stimuli-responsive unimolecular micelles from “Y”-shape armed amphiphilic star-like copolymer are designed for controlled drug delivery.

Review of Adaptive Programmable Materials and Their Bioapplications

Adaptive programmable materials have attracted increasing attention due to their high functionality, autonomous behavior, encapsulation, and site-specific confinement capabilities in various applications. Compared to conventional materials, adaptive programmable materials possess unique single-material architecture that can maintain, respond, and change their shapes and dimensions when they are subjected to surrounding environment changes, such as alternation in temperature, pH, and ionic strength. In this review, the most-recent advances in the design strategies of adaptive programmable materials are presented with respect to different types of architectural polymers, including stimuli-responsive polymers and shape-memory polymers. The diverse functions of these sophisticated materials and their significance in therapeutic agent delivery systems are also summarized in this review. Finally, the challenges for facile fabrication of these materials and future prospective are also discussed.

Biodegradable polymer scaffolds

Tissue engineering aims to repair the damaged tissue by transplantation of cells or introducing bioactive factors in a biocompatible scaffold. In recent years, biodegradable polymer scaffolds mimicking the extracellular matrix have been developed to promote the cell proliferation and extracellular matrix deposition. The biodegradable polymer scaffolds thus act as templates for tissue repair and regeneration. This article reviews the updated information regarding various types of natural and synthetic biodegradable polymers as well as their functions, physico-chemical properties, and degradation mechanisms in the development of biodegradable scaffolds for tissue engineering applications, including their combination with 3D printing.

Synthesis of Novel Temperature- and pH-Sensitive ABA Triblock Copolymers P(DEAEMA-co-MEO₂MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO₂MA-co-OEGMA): Micellization, Sol⁻Gel Transitions, and Sustained BSA Release

Novel temperature- and pH-responsive ABA-type triblock copolymers, P(DEAEMA-co-MEO₂MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO₂MA-co-OEGMA), composed of a poly(ethylene glycol) (PEG) middle block and temperature- and pH-sensitive outer blocks, were synthesized by atom transfer radical polymerization (ATRP). The composition and structure of the copolymer were characterized by ¹H NMR and gel permeation chromatography (GPC). The temperature- and pH-sensitivity, micellization, and the sol⁻gel transitions of the triblock copolymers in aqueous solutions were studied using transmittance measurements, surface tension, viscosity, fluorescence probe technique, dynamic light scattering (DLS), zeta-potential measurements, and transmission electron microscopy (TEM). The lower critical solution temperature (LCST) of the triblock copolymer, which contains a small amount of a weak base group, (N,N-diethylamino) ethyl methacrylate (DEAEMA), can be tuned precisely and reversibly by changing the solution pH. When the copolymer concentration was sufficiently high, increasing temperature resulted in the free-flowing solution transformation into a micellar gel. The sol-to-gel transition temperature (Tsol⁻gel) in aqueous solution will continue to decrease as solution concentration increases.

Recent Advances of Using Hybrid Nanocarriers in Remotely Controlled Therapeutic Delivery

The development of hybrid biomaterials has been attracting great attention in the design of materials for biomedicine. The nanosized level of inorganic and organic or even bioactive components can be combined into a single material by this approach, which has created entirely new advanced compositions with truly unique properties for drug delivery. The recent advances in using hybrid nanovehicles as remotely controlled therapeutic delivery carriers are summarized with respect to different nanostructures, including hybrid host-guest nanoconjugates, micelles, nanogels, core-shell nanoparticles, liposomes, mesoporous silica, and hollow nanoconstructions. In addition, the controlled release of guest molecules from these hybrid nanovehicles in response to various remote stimuli such as alternating magnetic field, near infrared, or ultrasound triggers is further summarized to introduce the different mechanisms of remotely triggered release behavior. Through proper chemical functionalization, the hybrid nanovehicle system can be further endowed with many new properties toward specific biomedical applications.

Emerging Supramolecular Therapeutic Carriers Based on Host-Guest Interactions

Recent advances in host-guest chemistry have significantly influenced the construction of supramolecular soft biomaterials. The highly selective and non-covalent interactions provide vast possibilities of manipulating supramolecular self-assemblies at the molecular level, allowing a rational design to control the sizes and morphologies of the resultant objects as carrier vehicles in a delivery system. In this Focus Review, the most recent developments of supramolecular self-assemblies through host-guest inclusion, including nanoparticles, micelles, vesicles, hydrogels, and various stimuli-responsive morphology transition materials are presented. These sophisticated materials with diverse functions, oriented towards therapeutic agent delivery, are further summarized into several active domains in the areas of drug delivery, gene delivery, co-delivery and site-specific targeting deliveries. Finally, the possible strategies for future design of multifunctional delivery carriers by combining host-guest chemistry with biological interface science are proposed.

Self-Assembly of Polyurethane Phosphate Ester with Phospholipid-Like Structures: Spherical, Worm-Like Micelles, Vesicles, and Large Compound Vesicles

Here, we report the preparation and self-assembly of amphiphilic polyurethane phosphate ester (PUP) polymers with phospholipid-like structures. The polymers, designed to have a hydrophilic phosphate head and two amphiphilic PPG-IPDI-MPEG (PU) tails were synthesized via coupling and phosphorylation reactions in sequence. These amphiphilic polymers could self-assemble into various interesting nanostructures in aqueous solution, such as spherical, worm-like micelles, vesicles, and large compound vesicles, depending on the hydrophobic chain length of PU tails and the initial polymer concentrations. It was found that the morphology transition is not only caused by the unique molecular structure of amphiphilic polyurethanes, but also influenced by the additional hydrophilic phosphate groups incorporated, which disturb the force balance governing the aggregation structures. This research supplies a new clue for the fabrication of well-defined nanostructures.

Facile Layer-by-Layer Self-Assembly toward Enantiomeric Poly(lactide) Stereocomplex Coated Magnetite Nanocarrier for Highly Tunable Drug Deliveries

A highly tunable nanoparticle (NP) system with multifunctionalities was developed as drug nanocarrier via a facile layer-by-layer (LbL) stereocomplex (SC) self-assembly of enantiomeric poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) in solution using silica-coated magnetite (Fe3O4@SiO2) as template. The poly(lactide) (PLA) SC coated NPs (Fe3O4@SiO2@-SC) were further endowed with different stimuli-responsiveness by controlling the outermost layer coatings with respective pH-sensitive poly(lactic acid)-poly(2-dimethylaminoethyl methacrylate) (PLA-D) and temperature-sensitive poly(lactic acid)-poly(N-isopropylacrylamide) (PLA-N) diblock copolymers to yield Fe3O4@SiO2@SC-D and Fe3O4@SiO2@SC-N NPs, respectively, while the superparamagnetic properties of Fe3O4 were maintained. TEM images show a clearly resolved core-shell structure with a silica layer and sequential PLA SC co/polymer coating layers in the respective NPs. The well-designed NPs possess a size distribution in a range of 220-270 nm and high magnetization of 70.8-72.1 emu/g [Fe3O4]. More importantly, a drug release study from the as-constructed stimuli-responsive NPs exhibited sustained release profiles and the rates of release can be tuned by variation of external environments. Further cytotoxicity and cell culture studies revealed that PLA SC coated NPs possessed good cell biocompatibility and the doxorubicin (DOX)-loaded NPs showed enhanced drug delivery efficiency toward MCF-7 cancer cells. Together with the strong magnetic sensitivity, the developed hybrid NPs demonstrate a great potential of control over the drug release at a targeted site. The developed coating method can be further optimized to finely tune the nanocarrier size and operating range of pHs and temperatures for in vivo applications.

Small molecule therapeutic-loaded liposomes as therapeutic carriers: from development to clinical applications

In this review, various methods and mechanisms for encapsulation of small therapeutic molecules in liposomes for targeted delivery and triggered release, as well as their potential in the clinical uses, are discussed.

Kinetics-dominated structure and stimuli-responsiveness in the assembly of colloidal nanotubes

In this paper, we discuss the molecular assembly kinetics of stimuli-responsive hydrogels prepared from imogolite, which is a rigid rod-like colloidal inorganic nanotube, and dicarboxylic acids.

Recent development of unimolecular micelles as functional materials and applications

Unimolecular micelles have high functionalities, encapsulation capabilities and site specific confinement abilities in various applications.

Recent Progress in Using Biomaterials as Vitreous Substitutes

Vitreous substitutes are crucial adjuncts during vitreo-retinal surgery for retinal diseases such as complicated retinal detachment, macular holes, complications of diabetic retinopathy, and ocular trauma involving posterior segment. In retinal detachment surgery, an internal tamponade agent is required to provide internal pressure for reattachment of the detached neurosensory retina. Current available options serve only as a temporary surgical adduct or short-term solution and are associated with inherent problems. Despite many years of intensive research, an ideal vitreous substitute remains elusive. Indeed, the development of an ideal vitreous substitute requires the concerted efforts of synthetic chemists and biomaterial engineers, as well as ophthalmic surgeons. In this review, we propose that polymeric hydrogels present the future of artificial vitreous substitutes due to its high water composition, optical transparency, and rheological properties that closely mimic the natural vitreous. In particular, thermosensitive smart hydrogels, with reversible sol to gel change, have emerged as the material class with the most potential to succeed as ideal vitreous substitutes, facilitating easy implementation during surgery. Importantly, these smart hydrogels also display potential as efficacious drug delivery systems.

Poly(ethylene glycol) conjugated poly(lactide)-based polyelectrolytes: synthesis and formation of stable self-assemblies induced by stereocomplexation

A series of pH-responsive amphiphilic poly(N,N-dimethylaminoethyl methacrylate)-block-poly(D-lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) conjugated with poly(ethylene glycol) (D-PDLA-D@PEG) and D-PLLA-D@PEG copolymers were synthesized using a combination of ring-opening polymerization and atom-transfer radical polymerization followed by sequential quaternization of PDMAEMA chains and azide-alkyne click reaction with alkyne-end PEG. Gel permeation chromatography, nuclear magnetic resonance, and Fourier transform infrared spectroscopy results demonstrate the successful synthesis of the copolymers, and the conjugated PEG percentages in the copolymers can be tuned by the feeding ratios in the quaternization reaction. Conjugating PEG onto the PDMAEMA segments also successfully facilitated the D-PDLA-D@PEG, D-PLLA-D@PEG, and its corresponding 1:1 D/L mixtures to be dissolved directly in aqueous solution at the desired concentration range without using any organic solvents unlike the copolymers without PEG conjugation (D-PDLA-D and D-PLLA-D). We demonstrate control over micellar size, charge, and stability via three different preparation pathways, i.e., solution pH, percentages of PEG conjugation in the copolymers, and formation of PLA stereocomplex in micellar core. Static and dynamic light scattering studies demonstrate that the size of the core-shell micelles increases when the solution pH is reduced due to the protonation of the PDMAEMA segments that caused the osmotic pressure within the micelle to increase until the micelles reached a maximum size. It is interesting to note that the micelles formed by 1:1 D/L mixtures have larger swelling ratios as well as aggregation number and hydrodynamic radius that do not change significantly with pH and dilution, respectively, as compared to micelles formed from individual D or L forms of the copolymers. The enhanced stability of the pH-responsive micelles prepared by direct dissolution of the 1:1 D/L mixtures of the PEG conjugated PLA-based polyelectrolytes in aqueous medium is attributed to the stereocomplex formation between PLLA and PDLA in the micellar core as confirmed by wide-angle X-ray scattering measurements.

Design of polyhedral oligomeric silsesquioxane (POSS) based thermo-responsive amphiphilic hybrid copolymers for thermally denatured protein protection applications

Hybrid micelles for simple and spontaneous protein protection using easily controllable temperature as the sole trigger in an “on-demand” fashion.