Nanogels of poly(acrylic acid): Uptake and release behavior with fluorescent oligothiophene-labeled bovine serum albumin

Non-Invasive Delivery of Insulin for Breaching Hindrances against Diabetes

Insulin is recognized as a crucial weapon in managing diabetes. Subcutaneous (s.c.) injections are the traditional approach for insulin administration, which usually have many limitations. Numerous alternative (non-invasive) slants through different routes have been explored by the researchers for making needle-free delivery of insulin for attaining its augmented absorption as well as bioavailability. The current review delineating numerous pros and cons of several novel approaches of non-invasive insulin delivery by overcoming many of their hurdles. Primary information on the topic was gathered by searching scholarly articles from PubMed added with extraction of data from auxiliary manuscripts. Many approaches (discussed in the article) are meant for the delivery of a safe, effective, stable, and patient friendly administration of insulin via buccal, oral, inhalational, transdermal, intranasal, ocular, vaginal and rectal routes. Few of them have proven their clinical efficacy for maintaining the glycemic levels, whereas others are under the investigational pipe line. The developed products are comprising of many advanced micro/nano composite technologies and few of them might be entering into the market in near future, thereby garnishing the hopes of millions of diabetics who are under the network of s.c. insulin injections.

Poly (acrylic acid)/tricalcium phosphate nanoparticles scaffold enriched with exosomes for cell-free therapy in bone tissue engineering: An in vivo evaluation

Introduction

This study aimed to assess the potential of poly (acrylic acid)/tricalcium phosphate nanoparticles (PAA/triCaPNPs) scaffold in terms of biocompatibility and osteoconductivity properties the in-vivo evaluation as well as to investigate the performance of PAA/triCaPNPs scaffold (with or without exosomes derived from UC-MSCs) for bone regeneration of rat critical-sized defect.

Methods

PAA/triCaPNPs scaffold was made from acrylic acid (AA) monomer, N,N'-methylenebisacrylamide (MBAA), sodium bicarbonate (SBC), and ammonium persulfate (APS) through freeze-drying method. For in vivo evaluation, we randomly divided 24 rats into three groups. The rat calvarial bone defects were treated as follows: (1) Control group: defects without any treatment, (2) scaffold group: defects treated with scaffold only, (3) scaffold+exo group: defects treated with scaffold enriched with exosomes (1 μg/μL, 150 μg per rat). Eight- and 12-weeks post-surgery, half of the animals were sacrificed and bone regeneration was examined through micro-computerized tomography (µ-CT), histological staining, and immunohistochemistry (IHC).

Results

Quantitative analysis based on µ-CT scan images at 8 and 12 weeks post-implantation clearly indicated that healing rate for defects that were filled with scaffold enriched with exosome was significantly higher than defects filled with scaffold without exosome. The H&E and Masson staining results revealed that more new bone-like form developed in the scaffold+exo group than that in control and scaffold groups. Further, IHC staining for osteocalcin and CD31 confirmed that more bone healing in the scaffold+exo group at 12 weeks could be associated with osteogenesis and angiogenesis concurrently.

Conclusion

In the present study, we aimed to investigate the therapeutic potential of PAA/triCaPNPs scaffold as a carrier of human UC-MSC-derived exosome to achieve the exosome-controlled release on calvarial bone defect. The in vivo results indicated that the exosome-enriched scaffold could effectively minify the defect area and improve the bone healing in rat model, and as such it could be an option for exosome-based therapy.

Preparation of poly(acrylic acid)/tricalcium phosphate nanoparticles scaffold: Characterization and releasing UC-MSCs derived exosomes for bone differentiation

Introduction

This study focused on preparing a multiscale three-dimensional (3D) scaffold using tricalcium phosphate nanoparticles (triCaPNPs) in a substrate of poly(acrylic acid) (PAA) polymer for controlled release of exosomes in bone tissue engineering.

Methods

A scaffold was fabricated with a material mixture containing acrylic acid (AA) monomer, N,N'-methylenebisacrylamide (MBAA), ammonium persulfate (APS), sodium bicarbonate (SBC), and triCaPNPs called composite scaffold (PAA/triCaPNPs) via cross-linking and freeze-drying methods. The synthesis process was easy and without complex multi-steps. Through mimicking the hybrid (organic-inorganic) structure of the bone matrix, we here chose triCaPNPs for incorporation into the PAA polymer. After assessing the physicochemical properties of the scaffold, the interaction of the scaffold with human umbilical cord mesenchymal stem cells (UC-MSCs) such as attachment, proliferation, and differentiation to osteoblast cells was evaluated. In addition, we used DiI-labeled exosomes to verify the exosome entrapment and release from the scaffold.

Results

The polymerization reaction of 3D scaffold was successful. Based on results of physicochemical properties, the presence of nanoparticles in the composite scaffold enhanced the mechanical stiffness, boosted the porosity with a larger pore size range, and offered better hydrophilicity, all of which would contribute to greater cell penetration, proliferation, and then better bone differentiation. In addition, our results indicated that our scaffold could take up and release exosomes, where the exosomes released from it could significantly enhance the osteogenic commitment of UC-MSCs.

Conclusion

The current research is the first study fabricating a multiscale scaffold using triCaPNPs in the substrate of PPA polymer using a cross-linker and freeze-drying process. This scaffold could mimic the nanoscale structure and chemical combination of native bone minerals. In addition, our results suggest that the PAA/triCaPNPs scaffold could be beneficial to achieve controlled exosome release for exosome-based therapy in bone tissue engineering.

Stimuli-responsive polypeptide nanogels for trypsin inhibition

A new type of hydrophilic, biocompatible, and biodegradable polypeptide nanogel depots loaded with the natural serine protease inhibitor α1-antitrypsin (AAT) was applied for the inhibition of the inflammatory mediator trypsin. Two types of nanogels were prepared from linear synthetic polypeptides based on biocompatible and biodegradable poly[N ⁵-(2-hydroxyethyl)-ʟ-glutamine-ran-N ⁵-propargyl-ʟ-glutamine-ran-N ⁵-(6-aminohexyl)-ʟ-glutamine]-ran-N ⁵-[2-(4-hydroxyphenyl)ethyl)-ʟ-glutamine] (PHEG-Tyr) or biocompatible N ^α-ʟ-lysine-grafted α,β-poly[(2-propyne)-ᴅ,ʟ-aspartamide-ran-(2-hydroxyethyl)-ᴅʟ-aspartamide-ran-(2-(4-hydroxyphenyl)ethyl)-ᴅʟ-aspartamide] (N ^α-Lys-NG). Both nanogels were prepared by HRP/H₂O₂-mediated crosslinking in inverse miniemulsions with pH and temperature-stimuli responsive behavior confirmed by dynamic light scattering and zeta potential measurements. The loading capacity of PHEG-Tyr and N ^α-Lys-NG nanogels and their release profiles were first optimized with bovine serum albumin. The nanogels were then used for loading and release of AAT. PHEG-Tyr and N ^α-Lys-NG nanogels showed different loading capacities for AAT with the maximum (20%) achieved with N ^α-Lys-NG nanogel. In both cases, the nanogel depots demonstrated a burst release of AAT during the first 6 h, which could be favorable for quick inhibition of trypsin. A consequent pilot in vitro inhibition study revealed that both PHEG-Tyr and N ^α-Lys-NG nanogels loaded with AAT successfully inhibited the enzymatic activity of trypsin. Furthermore, the inhibitory efficiency of the AAT-loaded nanogels was higher than that of only AAT. Interestingly, also non-loaded PHEG-Tyr and N ^α-Lys-NG nanogels were shown to effectively inhibit trypsin because they contain suitable amino acids in their structures that effectively block the active site of trypsin.

Preparation and Timed Release Properties of Self-Rupturing Gels

Swelling of polymeric hydrogels is sensitive to their cross-link densities. Here, we exploit this principle to prepare self-rupturing gels which are based on a commonly-used, nontoxic, and inexpensive polyelectrolyte, poly(acrylic acid), and are prepared through a simple and low-cost polymerization-based technique. The self-rupture of these covalently cross-linked gels is achieved by preparing them to have highly nonuniform cross-link densities. This heterogeneity in cross-linking leads to highly nonuniform swelling, which generates stresses that are high enough to induce gel rupture. The time required for this rupture to occur depends on the difference in the cross-link densities between the adjoining gel regions, gel size, order in which the variably cross-linked gel portions are synthesized, and on the ambient pH and ionic strength. Furthermore, when these self-rupturing gels are prepared to have liquid-filled (capsule-like) morphologies, they can act as timed/delayed release devices. The self-rupture of these capsules provides a burst payload release after a preprogrammed delay, which is on the timescale of days and can be easily tuned by varying the rupture time, i.e., by varying either the cross-link nonuniformity or the pH and ionic strength of the release media.