Effects of Microneedle Design Parameters on Hydraulic Resistance

Vaccine delivery alerts innate immune systems for more immunogenic vaccination

Vaccine delivery technologies are mainly designed to minimally invasively deliver vaccines to target tissues with little or no adjuvant effects. This study presents a prototype laser-based powder delivery (LPD) with inherent adjuvant effects for more immunogenic vaccination without incorporation of external adjuvants. LPD takes advantage of aesthetic ablative fractional laser to generate skin microchannels to support high-efficient vaccine delivery and at the same time creates photothermal stress in microchannel-surrounding tissues to boost vaccination. LPD could significantly enhance pandemic influenza 2009 H1N1 vaccine immunogenicity and protective efficacy as compared with needle-based intradermal delivery in murine models. The ablative fractional laser was found to induce host DNA release, activate NLR family pyrin domain containing 3 inflammasome, and stimulate IL-1β release despite their dispensability for laser adjuvant effects. Instead, the ablative fractional laser activated MyD88 to mediate its adjuvant effects by potentiation of antigen uptake, maturation, and migration of dendritic cells. LPD also induced minimal local or systemic adverse reactions due to the microfractional and sustained vaccine delivery. Our data support the development of self-adjuvanted vaccine delivery technologies by intentional induction of well-controlled tissue stress to alert innate immune systems for more immunogenic vaccination.

Novel microinjector for carrying bone substitutes for bone regeneration in periodontal diseases

BACKGROUND/PURPOSE

Traditionally, guide bone regeneration (GBR) was a widely used method for repairing bone lost from periodontal disease. There were some disadvantages associated with the GBR method, such as the need for a stable barrier membrane and a new creative cavity during the surgical process. To address these disadvantages, the purpose of this study was to evaluate a novel microinjector developed for dental applications. The microinjector was designed to carry bone graft substitutes to restore bone defects for bone regeneration in periodontal diseases. The device would be used to replace the GBR method.

METHODS

In this study, the injected force and ejected volume of substitutes (including air, water, and ethanol) were defined by Hooke's law (n = 3). The optimal particle size of bone graft substitutes was determined by measuring the recycle ratio of bone graft substitutes from the microinjector (n = 3). Furthermore, a novel agarose gel model was used to evaluate the feasibility of the microinjector.

RESULTS

The current study found that the injected force was less than 0.4 N for obtaining the ejected volume of approximately 2 mL, and when the particle size of tricalcium phosphate (TCP) was smaller than 0.5 mm, 80% TCP could be ejected from the microinjector. Furthermore, by using an agarose model to simulate the periodontal soft tissue, it was also found that bone graft substitutes could be easily injected into the gel.

CONCLUSION

The results confirmed the feasibility of this novel microinjector for dental applications to carry bone graft substitutes for the restoration of bone defects of periodontal disease.

Fiberoptic microneedle device facilitates volumetric infusate dispersion during convection-enhanced delivery in the brain

BACKGROUND AND OBJECTIVES

A fiberoptic microneedle device (FMD) was designed and fabricated for the purpose of enhancing the volumetric dispersal of macromolecules delivered to the brain through convection-enhanced delivery (CED) by concurrent delivery of sub-lethal photothermal hyperthermia. This study's objective was to demonstrate enhanced dispersal of fluid tracer molecules through co-delivery of 1,064  nm laser energy in an in vivo rodent model.

MATERIALS AND METHODS

FMDs capable of co-delivering fluids and laser energy through a single light-guiding capillary tube were fabricated. FMDs were stereotactically inserted symmetrically into both cerebral hemispheres of 16 anesthetized rats to a depth of 1.5  mm. Laser irradiation (1,064 nm) at 0 (control), 100, and 200 mW was administered concurrently with CED infusions of liposomal rhodamine (LR) or gadolinium-Evans blue-serum albumin conjugated complex (Gd-EBA) at a flow rate of 0.1 µl/min for 1 hour. Line pressures were monitored during the infusions. Rodents were sacrificed immediately following infusion and their brains were harvested, frozen, and serially cryosectioned for histopathologic and volumetric analyses.

RESULTS

Analysis by ANOVA methods demonstrated that co-delivery enhanced volumetric dispersal significantly, with measured volumes of 15.8  ±  0.6 mm(3) for 100 mW compared to 10.0  ±  0.4 mm(3) for its fluid only control and 18.0  ±  0.3 mm(3) for 200 mW compared to 10.3  ±  0.7 mm(3) for its fluid only control. Brains treated with 200 mW co-delivery exhibited thermal lesions, while 100 mW co-deliveries were associated with preservation of brain cytoarchitecture.

CONCLUSION

Both lethal and sub-lethal photothermal hyperthermia substantially increase the rate of volumetric dispersal in a 1 hour CED infusion. This suggests that the FMD co-delivery method could reduce infusion times and the number of catheter insertions into the brain during CED procedures.

Intracranial hyperthermia through local photothermal heating with a fiberoptic microneedle device

BACKGROUND AND OBJECTIVES

The fiberoptic microneedle device (FMD) seeks to leverage advantages of both laser-induced thermal therapy (LITT) and convection-enhanced delivery (CED) to increase volumetric dispersal of locally infused chemotherapeutics through sub-lethal photothermal heat generation. This study focused on determination of photothermal damage thresholds with 1,064 nm light delivered through the FMD into in vivo rat models.

MATERIALS AND METHODS

FMDs capable of co-delivering laser energy and fluid agents were fabricated through a novel off-center splicing technique involving fusion of a multimode fiberoptic to light-guiding capillary tubing. FMDs were positioned at a depth of 2.5 mm within the cerebrum of male rats with fluoroptic temperature probes placed within 1 mm of the FMD tip. Irradiation (without fluid infusion) was conducted at laser powers of 0 (sham), 100, 200, 500, or 750 mW. Evans blue-serum albumin conjugated complex solution (EBA) and laser energy co-delivery were performed in a second set of preliminary experiments.

RESULTS

Maximum, steady-state temperatures of 38.7 ± 1.6 and 42.0 ± 0.9 °C were measured for the 100 and 200 mW experimental groups, respectively. Histological investigation demonstrated needle insertion damage alone for sham and 100 mW irradiations. Photothermal damage was detected at 200 mW, although observable thermal damage was limited to a small penumbra of cerebral cortical microcavitation and necrosis that immediately surrounded the region of FMD insertion. Co-delivery of EBA and laser energy presented increased volumetric dispersal relative to infusion-only controls.

CONCLUSION

Fluoroptic temperature sensing and histopathological assessments demonstrated that a laser power of 100 mW results in sub-lethal brain hyperthermia, and the optimum, sub-lethal target energy range is likely 100-200 mW. The preliminary FMD-CED experiments confirmed the feasibility of augmenting fluid dispersal using slight photothermal heat generation, demonstrating the FMD's potential as a way to increase the efficacy of CED in treating MG.