Phosphate Glass Microspheres Research Articles

Zinc phosphate glass microspheres promoted mineralization and expression of BMP2 in MC3T3-E1 cells.

Degradable phosphate glasses have shown favorable properties for tissue engineering. By changing the composition of the glasses, the degradation rate, and ion release are controllable. Zinc oxide can function as a glass network modifier and has been shown to play a positive role in bone formation. Also, phosphate glasses can easily be processed into microspheres, which can be used as microcarriers. This study aims to develop zinc phosphate glasses microspheres and explore the optimized size and composition for applications in bone tissue engineering. Zinc-titanium-calcium-sodium phosphate glasses with 0, 1, 3, 5, or 10 mol % zinc oxide were prepared and processed into microspheres. The smaller microspheres ranged in size from 50 to 106 μm, while the larger ones ranged from 106 to 150 μm. The characteristics of glasses were examined. The osteoblastic cell line MC3T3-E1 was cultured on the surface of microspheres and the cell viability was examined. To evaluate osteogenic differentiation, Alizarin Red S staining, quantitative reverse transcription polymerase chain reaction, and western blot analysis were performed after 14 days. Different sizes of zinc phosphate glass microspheres were successfully made. The glass microspheres with <10 mol % zinc oxide were able to support the adhesion and proliferation of MC3T3-E1 cell lines. The relative gene expression of BMP2 was significantly upregulated in the smaller glass microspheres containing 3 mol % zinc oxide (26-fold, p < .001) and both sizes of microspheres containing 5 mol % zinc oxide (smaller: 27-fold, p < .001; larger: 35-fold, p < .001). Additionally, cluster formation was observed in glass microspheres after 14 days, and the mineralization of MC3T3-E1 cell lines was promoted. Based on these findings, the glass microspheres containing 3-5 mol % of zinc oxide can promote osteogenic differentiation for MC3T3-E1 cells.

Phosphate Glass Microspheres with Silver Nanoparticles for Whispering Gallery Mode Resonators.

Glass microspheres have gained significant attention over the years in the field of photonics due to their application in whispering gallery mode (WGM) microresonator platforms. However, the synthesis of glass spheres in the micro regime remains challenging, while it relies mostly on complicated synthetic methods or sol-gel chemistry. Herein, we demonstrate the controlled formation of phosphate glass microspheres by means of a simple, fast, low-temperature, post-glass melting thermal treatment of previously quenched glass. Moreover, we report on the simultaneous formation of silver nanoparticles (AgNPs) on the surface of glass spheres upon the same treatment. The formation of metal nanoparticles onto the glass spheres induces attractive optical and plasmonic properties, believed to be suitable for WGM resonator-based applications, as well as a wide range of optoelectronic, photonic, and sensing applications.

Development of samarium-doped phosphate glass microspheres for internal radiotheranostic applications

Internal radiotherapy delivers radioactive sources inside the body, near to or into malignant tumours, which may be particularly effective when malignancies are not responding to external beam radiotherapy. A pure beta emitter, 90Y, is currently used for internal radiotherapy. However, theranostic radionuclide-doped microspheres can be developed by incorporating 153Sm, which emits therapeutic beta and diagnostic gamma energies. This study investigated the production of high concentrations of samarium-content doped phosphate-based glass microspheres. The glass P60 (i.e. 60P2O5-25CaO-15Na2O) was mixed with Sm2O3 at ratios of 75:25 (G75:Sm25), 50:50 (G50:Sm50) and 25:75 (G25:Sm75) and processed via flame spheroidisation. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) confirmed the microsphere uniformity with significantly high samarium content up to 44 % in G25:Sm75. Via X-ray diffraction (XRD) analysis, samarium-doped microspheres appeared to be glass–ceramic in nature. Mass-loss, size and pH changes were performed over 28 days, revealing a significant increase in samarium microsphere stability. After 15 min of neutron activation (neutron flux 3.01 × 1013 n.cm−2.s−1), the specific activity of the microspheres (G75:Sm25, G50:Sm50 and G25:Sm75) was 0.28, 0.54 and 0.58 GBq.g−1, respectively. Therefore, the samarium microspheres produced in this study provide great potential for improving internal radiotherapy treatment for liver cancer by avoiding complex procedures and using less microspheres with shorter irradiation time.

High-Q lasing in Nd3+-doped phosphate glass microsphere resonators.

Nd3+-doped glasses are the most widely used laser gain media. However, Nd3+-doped non-silica microsphere lasers generally have lower quality (Q) factors due to the presence of non-radiative energy-loss impurities in traditional glass systems. In this work, we report the first, to the best of our knowledge, Nd3+-doped phosphate glass microsphere laser with the highest Q-factor of 1.54 × 106 among all Nd3+-doped non-silica glass microsphere lasers. Whispering gallery modes in the 1020-1120-nm band can be obtained for a typical microsphere with a diameter of 82.57 µm. When the pump power exceeds the threshold of 0.17 mW, single- and multi-mode microsphere lasing can be generated under 808-nm laser diode (LD) pumping. Typical Q-factors of the phosphate glass microspheres can reach 106, which is at least an order of magnitude higher than those of other Nd3+-doped non-silica glass microsphere lasers. The Nd3+-doped phosphate glass microsphere laser reported in this work can be considered as an active optical/photonic device with low pump thresholds.

Process parameter optimisation for manufacturing porous bioactive silicate glass microspheres via flame spheroidisation: The goldilocks effect

This study investigated the influence of flame spheroidisation process parameters for successfully manufacturing solid (dense) and highly porous microspheres from Food and Drug Administration approved bioactive 45S5 glass and 45S5 with addition of viscosity modifiers (i.e. 2 and 5 mol% borax and V2O5), compared against successfully processed phosphate glass microspheres (termed P40). Characterisation studies performed included thermal analysis (SDT), glass viscosity measurements using high temperature rotational viscometry and hot stage microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis.This study revealed that aside from intrinsic material properties (i.e. melt temperature and viscosity profiles), process parameters including starting glass particle size, cooling rate and gas flow rates were important factors in achieving the desired porous glass microsphere morphology. Considering the above influential factors, a processing model has been proposed for the manufacture of highly porous microspheres from bioactive silicate glasses.

Osteogenic potential of solid and porous phosphate glass microspheres as pulp capping materials

This study investigated the morphology (Scanning Electron Microscope), chemistry (Elemental Analysis (EDX), Raman Spectroscopy and X-ray diffraction), thermal characteristics, cytocompatibility, and osteogenic potential of solid and porous phosphate-based glass microspheres for potential use as pulp-capping materials. Cytocompatibility was investigated using human dental pulp stem cells (hDPSCs) through both direct and indirect (extracts) contact tests. Cells grown in normal cell culture medium and 10% dimethyl sulfoxide served as positive and negative controls, respectively. Unlike solid glass microspheres (GMs), porous GMs showed higher CaO mol% and crystalline structure. Both types of GMs supported the attachment, spreading, and viability of hDPSCs similar to the positive control. Cells grown in GMs’ extracts showed even higher viability, but less mineralization than those grown in direct contact with GMs. The presence of osteogenic supplements however did not have a significant effect on mineralisation. Accordingly, both solid and porous GMs show useful applicability as pulp-capping materials.

Antibacterial effect of titanium dioxide-doped phosphate glass microspheres filled total-etch dental adhesive on S. mutans biofilm

Abstract Purpose to improve the antibacterial action of a two-step total-etch dental adhesive by using titanium dioxide-doped phosphate glass microspheres (GMs) without affecting its penetration ability. Materials and methods Five and 10 wt% of APTES silanized [surface treated with 3-Aminopropyltriethoxysilane (APTES)] and non-silanized GMs have been used as a filler to Adper™ Single Bond 2 Refill. The morphology, chemistry and ζ - potential of GMs have been investigated using scanning electron microscopy, Fourier transform infra-red (FTIR) spectroscopy and Zeta-sizer respectively. The chemistry and antibacterial action of filled adhesive have been investigated using FTIR and nitrocellulose filter membranes (NFM) S. mutans biofilm model respectively. The number of colony forming units (CFU) per NFM was considered. The contact angle and microtensile bond strength of adhesives to mid-coronal dentin, as a measure of its penetration ability, have been investigated using a Drop Shape Analyzer and microtensile testing machine respectively. Adper™ Single Bond 2 Refill was used as a control. Results The size of GMs varied from 60 to 200 μm. The silanization process was confirmed by reduction in ζ-potential [-7 (±2) mV] and the presence of amide (1500-1600 cm−1), C–N (1380 cm−1), Si–O–Si (1096 cm−1) and Si–O–C (780 cm−1) peaks. Incorporation of GMs had no adverse effect on monomer conversion. All tested adhesives including the control showed significantly higher antibacterial action (~5–7 log10 reduction in CFU) than the NFM control. All filled adhesives showed significantly higher antibacterial action (~1–2 log10 reduction in CFU) than the control adhesive. The non-silanized GMs filled adhesives showed the highest antibacterial action against S. mutans biofilm formation. The presence of silanized GMs did not affect the wetting but increased the microtensile bond strength of the adhesive to dentin. Conclusion Glass microsphere modified adhesives could be promising to reduce the possibility of recurrent caries around restorations.

基于磷酸盐玻璃微球腔的全光调谐光纤滤波器

基于磷酸盐玻璃微球腔的全光调谐光纤滤波器

Characterisation of osteogenic and vascular responses of hMSCs to Ti-Co doped phosphate glass microspheres using a microfluidic perfusion platform

Using microspherical scaffolds as building blocks to repair bone defects of specific size and shape has been proposed as a tissue engineering strategy. Here, phosphate glass (PG) microcarriers doped with 5 mol % TiO2 and either 0 mol % CoO (CoO 0%) or 2 mol % CoO (CoO 2%) were investigated for their ability to support osteogenic and vascular responses of human mesenchymal stem cells (hMSCs). Together with standard culture techniques, cell-material interactions were studied using a novel perfusion microfluidic bioreactor that enabled cell culture on microspheres, along with automated processing and screening of culture variables. While titanium doping was found to support hMSCs expansion and differentiation, as well as endothelial cell-derived vessel formation, additional doping with cobalt did not improve the functionality of the microspheres. Furthermore, the microfluidic bioreactor enabled screening of culture parameters for cell culture on microspheres that could be potentially translated to a scaled-up system for tissue-engineered bone manufacturing.

Formulating injectable pastes of porous calcium phosphate glass microspheres for bone regeneration applications

Current trends in regenerative medicine treatments for bone repair applications focus on cell-based therapies. These aim to deliver the treatment via a minimally invasive injection to reduce patient trauma and to improve efficacy. This paper describes the injectability of porous calcium phosphate glass microspheres to be used for bone repair based on their formulation, rheology and flow behavior. The use of excipients (xanthan gum, methyl cellulose and carboxyl methyl cellulose) were investigated to improve flow performance. Based on our results, the flow characteristics of the glass microsphere pastes vary according to particle size, surface area, and solid to liquid ratio, as well as the concentration of viscosity modifiers used. The optimal flow characteristics of calcium phosphate glass microsphere pastes was found to contain 40 mg/mL of xanthan gum which increased viscosity whilst providing elastic properties (∼29,000 Pa) at shear rates that mirror the injection process and the resting period post injection, preventing the glass microspheres from both damage and dispersion. It was established that a base formulation must contain 1 g of glass microspheres (60-125 μm in size) per 1 mL of cell culture media, or 0.48 g of glass microspheres of sizes between 125 and 200 μm. Furthermore, the glass microsphere formulations with xanthan gum were readily injectable via a syringe-needle system (3-20 mL, 18G and 14G needles), and have the potential to be utilized as a cell (or other biologics) delivery vehicle for bone regeneration applications.

In vitro cellular testing of strontium/calcium substituted phosphate glass discs and microspheres shows potential for bone regeneration.

Phosphate‐based glasses (PBGs) are ideal materials for regenerative medicine strategies because their composition, degradation rates, and ion release profiles can easily be controlled. Strontium has previously been found to simultaneously affect bone resorption and deposition. Therefore, by combining the inherent properties of resorbable PBG and therapeutic activity of strontium, these glasses could be used as a delivery device of therapeutic factors for the treatment of orthopaedic diseases such as osteoporosis. This study shows the cytocompatibility and osteogenic potential of PBGs where CaO is gradually replaced by SrO in the near invert glass system 40P2O5·(16‐x)CaO·20Na2O·24MgO·xSrO (x = 0, 4, 8, 12, and 16 mol%). Direct seeding of MG63 cells onto glass discs showed no significant difference in cell metabolic activity and DNA amount measurement across the different formulations studied. Cell attachment and spreading was confirmed via scanning electron microscopy (SEM) imaging at Days 3 and 14. Alkaline phosphatase (ALP) activity was similarly maintained across the glass compositions. Follow‐on studies explored the effect of each glass composition in microsphere conformation (size: 63‐125 μm) on human mesenchymal stem cells (hMSCs) in 3D cultures, and analysis of cell metabolic activity and ALP activity showed no significant differences at Day 14 over the compositional range investigated, in line with the observations from MG63 cell culture studies. Environmental SEM and live cell imaging at Day 14 of hMSCs seeded on the microspheres showed cell attachment and colonisation of the microsphere surfaces, confirming these formulations as promising candidates for regenerative medicine strategies addressing compromised musculoskeletal/orthopaedic diseases.

Assessing behaviour of osteoblastic cells in dynamic culture conditions using titanium-doped phosphate glass microcarriers

Tissue engineering is a promising approach for bone regeneration; yet challenges remain that limit successful translation to patients. It is necessary to understand how real-world manufacturing processes will affect the constituent cells and biomaterials that are needed to create engineered bone. Bioactive phosphate glasses processed into microspheres are an attractive platform for expanding bone-forming cells and also for driving their osteogenic differentiation and maturation. The aim of this study was to assess whether Ti-doped phosphate glass microspheres could support osteoblastic cell responses in dynamic cell culture environments. Dynamic culture conditions were achieved using microwell studies under orbital agitation. Dimensionless parameters such as the Froude number were used to inform the choice of agitation speeds, and the impact on cell proliferation and microunit formation was quantified. We found that phosphate glass microspheres doped with titanium dioxide at both 5 and 7 mol% provided a suitable biomaterial platform for effective culture of MG63 osteoblastic cells and was not cytotoxic. Dynamic culture conditions supported expansion of MG63 cells and both 150 and 300 rpm orbital shake resulted in higher cell yield than static cultures at the end of the culture (day 13). The Froude number analysis provided insight into how the microunit size could be manipulated to enable an appropriate agitation speed to be used, while ensuring buoyancy of the microunits. These small-scale experiments and analyses provide understanding of the impact of fluid flow on cell expansion that will have increasing importance when scaling up to process technologies that can deliver clinical quantities of cell-microsphere units. Such knowledge will enable future engineering of living bone-like material using processing systems such as bioreactors that use mixing and agitation for nutrient transfer, therefore introducing cells to dynamic culture conditions.

Porous calcium phosphate glass microspheres for orthobiologic applications

Orthobiologics is a rapidly advancing field utilising cell-based therapies and biomaterials to enable the body to repair and regenerate musculoskeletal tissues. This paper reports on a cost-effective flame spheroidisation process for production of novel porous glass microspheres from calcium phosphate-based glasses to encapsulate and deliver stem cells. Careful selection of the glass and pore-forming agent, along with a manufacturing method with the required processing window enabled the production of porous glass microspheres via a single-stage manufacturing process. The morphological and physical characterisation revealed porous microspheres with tailored surface and interconnected porosity (up to 76 ± 5%) with average pore size of 55 ± 8 µm and surface areas ranging from 0.34 to 0.9 m2 g−1. Furthermore, simple alteration of the processing parameters produced microspheres with alternate unique morphologies, such as with solid cores and surface porosity only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. Furthermore, cytocompatibility of the microspheres was assessed using human mesenchymal stem cells via direct cell culture experiments and analysis confirmed that they had migrated to within the centre of the microspheres. The novel microspheres developed have huge potential for tissue engineering and regenerative medicine applications. Statement of SignificanceThis manuscript highlights a simple cost-effective one-step process for manufacturing porous calcium phosphate-based glass microspheres with varying control over surface pores and fully interconnected porosity via a flame spheroidisation process. Moreover, a simple alteration of the processing parameters can produce microspheres which have a solid core with surface pores only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. The paper also shows that stem cells not only attach and proliferate but more importantly migrate to within the core of the porous microspheres, highlighting applications for bone tissue engineering and regenerative medicine.

WHISPERING GALLERY MODE LASERS IN ERBIUM/YTTERBIUM CODOPED PHOSPHATE GLASSES

The study of whispering gallery mode laser in Er3+/Yb3+ co-doped phosphate glass microsphere has been reported. The coupling was carried out by fiber half taper technique. The microsphere lasers have been studied under pumping at 980 nm, to take full advantage of energy transfer effect from ion Ytterbium to ion Erbium. The observed lasing range extends from 1533 nm to 1612 nm.

Towards modular bone tissue engineering using Ti-Co-doped phosphate glass microspheres: cytocompatibility and dynamic culture studies.

The production of large quantities of functional vascularized bone tissue ex vivo still represent an unmet clinical challenge. Microcarriers offer a potential solution to scalable manufacture of bone tissue due to their high surface area-to-volume ratio and the capacity to be assembled using a modular approach. Microcarriers made of phosphate bioactive glass doped with titanium dioxide have been previously shown to enhance proliferation of osteoblast progenitors and maturation towards functional osteoblasts. Furthemore, doping with cobalt appears to mimic hypoxic conditions that have a key role in promoting angiogenesis. This characteristic could be exploited to meet the clinical requirement of producing vascularized units of bone tissue. In the current study, the human osteosarcoma cell line MG-63 was cultured on phosphate glass microspheres doped with 5% mol titanium dioxide and different concentrations of cobalt oxide (0%, 2% and 5% mol), under static and dynamic conditions (150 and 300 rpm on an orbital shaker). Cell proliferation and the formation of aggregates of cells and microspheres were observed over a period of two weeks in all glass compositions, thus confirming the biocompatibility of the substrate and the suitability of this system for the formation of compact micro-units of tissue. At the concentrations tested, cobalt was not found to be cytotoxic and did not alter cell metabolism. On the other hand, the dynamic environment played a key role, with moderate agitation having a positive effect on cell proliferation while higher agitation resulting in impaired cell growth. Finally, in static culture assays, the capacity of cobalt doping to induce vascular endothelial growth factor (VEGF) upregulation by osteoblastic cells was observed, but was not found to increase linearly with cobalt oxide content. In conclusion, Ti-Co phosphate glasses were found to support osteoblastic cell growth and aggregate formation that is a necessary precursor to tissue formation and the upregaulation of VEGF production can potentially support vascularization.

Silver iodide phosphate glass microsphere resonator integrated on an optical fiber taper.

In this Letter, we demonstrate the fabrication and characterization of a robust and functional whispering gallery mode (WGM) resonating system based on a silver iodide phosphate glass microsphere melted on an optical fiber taper. The fabrication process is presented, together with spectral characterization of the device. The effect of the thermal annealing of the soft glass resonator on the whispering gallery modes' excitation and Q-factor is shown and discussed.

Room-temperature preparation of phosphate glass microspheres as carriers for therapeutic agents

Event Abstract Back to Event Room-temperature preparation of phosphate glass microspheres as carriers for therapeutic agents Arash Momeni1, Iain Gibson1 and Mark Filiaggi1, 2 1 Dalhousie University, Applied Oral Sciences, Canada 2 Dalhousie University, School of Biomedical Engineering, Canada Introduction: Polymeric microspheres are widely accepted as carriers for therapeutic agents (TA) due to their excellent biocompatibility and biodegradability, however they lack osteoconductivity and mechanical stiffness which glass microspheres (GMS) could offer in dental or bone-related applications. GMS are only prepared by high temperature methods (e.g. propane torch) that preclude loading of TA. Glass particles can be prepared by sol-gel methods and can be loaded by direct addition of the TA to the sol or by subsequent soaking of particles in the TA solution. However, these particles are typically irregular in shape, brittle due to porosity and display low TA encapsulation efficiency. We are describing here for the first time the feasibility of preparing spherical phosphate glass particles with excellent TA loading using polyphosphate coacervates. Materials and Methods: Sodium polyphosphate (NaPP) was prepared in-house [1] and dissolved in water (1% (g/mL)). 1M CaCl2 solution was then added to reach a Ca/P mole ratio of 0.5 forming polyphosphate coacervate [2], which was subsequently collected, freeze-dried and mixed with minocycline (antibiotic) solution (1.6±0.2% minocycline/dry coacervate (wt.)). To form the GMS, 9g of polycaprolactone (thickening agent) was dissolved in 150mL chloroform, followed by addition of 1mL of Span80 (emulsifier). To this solution, 1mL of drug-loaded coacervate was added and mixed using an overhead stirrer at 2000rpm for 90min prior to adding 300mL of acetone and mixing at 400rpm for 3hr. GMS were collected by centrifugation and washed with fresh chloroform and acetone. Cross-sectional SEM imaging of GMS was obtained after imbedding in cured resin, polishing and then applying a conductive coating. Drug loading and encapsulation efficiency were determined by measuring minocycline absorbance at 400nm. Composition was determined by energy dispersive X-ray (EDX) and inductively coupled plasma (ICP). Particle size was assessed using laser diffraction. Results and Discussion: GMS preparation is described schematically in Fig. 1. Ca2+ screens the charge on NaPP chains to yield a coacervate, a polymer-rich phase that separates form the original solution [2]. TA is mixed with the coacervate and then dispersed inside a non-solvent (Chloroform) to obtain spherical particles by surface tension, followed by water extraction (acetone addition) to transform the coacervate to glass. GMS obtained by this process were found to be highly spherical, with homogeneous composition as demonstrated by EDX mapping (Fig. 2). EDX results are in agreement with ICP data indicating a GMS Ca/P mole ratio of 0.4, similar to that observed in the precursor coacervate. A distribution of GMS sizes, between 1-200µm, was obtained that could subsequently be sieved to get to a desired bead size. Encapsulation efficiency was 62±16% (n=6) that is expectedly high as minocycline solubility in acetone and chloroform is limited, and drug loading was 1.0±0.2% (n=6). Higher drug loading is presumably feasible by introducing more minocycline to coacervate initially. Conclusion: Room-temperature preparation of therapeutically loaded phosphate glass microspheres is possible using polyphosphate coacervate precursors. Currently we are focused on minocycline elution studies and application of these microspheres in periodontitis treatment.

Development of Phosphate Glass Microspheres Containing Holmium for Selective Internal Radiotherapy

Selective internal radiotherapy is used to treat hepatocellular carcinoma. Glass microspheres containing β- particle emitter radionuclides are introduced into the liver close to the tumor. The microspheres are trapped in the arterioles which feed the tumor. The irradiation with β- particles can cause the death of cancer cells. In this work the development of phosphate glass microspheres containing holmium is proposed. 165Ho has a high cross section for neutron absorption enabling the production of 166Ho which decays to 166Er by emitting a β- particle. The microspheres were produced using the flame method and characterized by different techniques to evaluate their potential use in radiotherapy. Microspheres with suitable morphology, size, density, and holmium concentration were obtained.

Titanium phosphate glass microspheres for bone tissue engineering

We have demonstrated the successful production of titanium phosphate glass microspheres in the size range of ∼10–200μm using an inexpensive, efficient, easily scalable process and assessed their use in bone tissue engineering applications. Glasses of the following compositions were prepared by melt-quench techniques: 0.5P2O5–0.4CaO–(0.1−x)Na2O–xTiO2, where x=0.03, 0.05 and 0.07mol fraction (denoted as Ti3, Ti5 and Ti7 respectively). Several characterization studies such as differential thermal analysis, degradation (performed using a novel time lapse imaging technique) and pH and ion release measurements revealed significant densification of the glass structure with increased incorporation of TiO2 in the glass from 3 to 5mol.%, although further TiO2 incorporation up to 7mol.% did not affect the glass structure to the same extent. Cell culture studies performed using MG63 cells over a 7-day period clearly showed the ability of the microspheres to provide a stable surface for cell attachment, growth and proliferation. Taken together, the results confirm that 5mol.% TiO2 glass microspheres, on account of their relative ease of preparation and favourable biocompatibility, are worthy candidates for use as substrate materials in bone tissue engineering applications.

Thermo-Optical Tuning of Whispering Gallery Modes in Erbium:Ytterbium Doped Glass Microspheres to Arbitrary Probe Wavelengths

We present experimental results on an all-optical, thermally-assisted technique for broad range tuning of microsphere cavity resonance modes to arbitrary probe wavelengths. An erbium:ytterbium co-doped phosphate glass (Schott IOG-2) microsphere is pumped at 978 nm via the supporting stem and the heat generated by absorption of the pump light expands the cavity and changes the refractive index. This is a robust tuning method that decouples the pump from the probe and allows fine tuning of the microsphere's whispering gallery modes. Pump/probe experiments were performed to demonstrate thermo-optical tuning to specific probe wavelengths, including the 5S1/2 F= 3 to 5P3/2 F'= 4 laser cooling transition of rubidium-85. This is of particular interest for cavity quantum electrodynamics (QED)-type experiments, while the broad tuning range achievable is useful for integrated photonic devices, including sensors and modulators.